examples/tcp: fix lifetime for smoltcp bump

.github/workflows/ci.yml

@@ -1,117 +0,0 @@
-name: Continuous Integration
-
-on:
-  push:
-    branches: [master]
-
-  pull_request:
-    branches: [master]
-
-env:
-  CARGO_TERM_COLOR: always
-
-jobs:
-  style:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: stable
-          override: true
-          components: rustfmt
-
-      - name: Style Check
-        uses: actions-rs/cargo@v1
-        with:
-          command: fmt
-          args: --all -- --check
-
-  clippy:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: stable
-          target: thumbv7em-none-eabihf
-          override: true
-          components: clippy
-
-      - name: Clippy Check
-        uses: actions-rs/cargo@v1
-        with:
-          command: clippy
-          args: --all-features
-
-  documentation:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-
-      - uses: actions-rs/toolchain@v1
-        with:
-          profile: minimal
-          toolchain: stable
-          target: thumbv7em-none-eabihf
-          override: true
-
-      - name: Cargo Doc
-        uses: actions-rs/cargo@v1
-        with:
-          command: doc
-          args: --all-features
-
-  audit:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v2
-      - name: Cargo Audit
-        uses: actions-rs/audit-check@v1
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}
-
-  compile:
-    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        toolchain:
-          - stable
-          - beta
-
-    steps:
-      - uses: actions/checkout@v2
-
-      - name: Install Rust ${{ matrix.toolchain }}
-        uses: actions-rs/toolchain@v1
-        with:
-          toolchain: ${{ matrix.toolchain }}
-          target: thumbv7em-none-eabihf
-          override: true
-
-      - name: Cargo Check
-        uses: actions-rs/cargo@v1
-        with:
-          command: check
-          args: --verbose --all-features
-
-      - name: Cargo Build
-        uses: actions-rs/cargo@v1
-        with:
-          command: build
-          args: --all-features
-
-      - name: Cargo Build [Release]
-        uses: actions-rs/cargo@v1
-        with:
-          command: build
-          args: --release --all-features
-
-      - name: Cargo Build [Examples]
-        uses: actions-rs/cargo@v1
-        with:
-          command: build
-          args: --examples --all-features

Cargo.toml

@@ -1,9 +1,9 @@
 [package]
 categories = ["embedded", "no-std"]
 name = "enc424j600"
-description = "Embbeded Rust Ethernet driver for ENC424J600 Ethernet controller with SPI interface"
-authors = ["Harry Ho <hh@m-labs.hk>", "Dip Cheung <dc@m-labs.hk>"]
-version = "0.3.0"
+description = "Embbeded Rust Ethernet driver for ENC424J600 Ethernet controller with SPI interface, compatible with STM32F4xx"
+authors = ["Harry Ho <hh@m-labs.hk>"]
+version = "0.2.0"
 keywords = ["ethernet", "eth", "enc424j600", "stm32", "stm32f4xx"]
 repository = "https://git.m-labs.hk/M-Labs/ENC424J600"
 edition = "2018"
@@ -13,30 +13,37 @@ license = "BSD-2-Clause"
 volatile-register = "0.2"
 aligned = "0.3"
 embedded-hal = "0.2"
-smoltcp = { version = "0.7.0", default-features = false, features = [ "socket-raw", "proto-ipv4",
-    "proto-ipv6", "socket-tcp", "ethernet"], optional = true }
-cortex-m = {version = "0.5", optional = true }
-
+smoltcp = { version = "0.7.0", default-features = false, features = ["proto-ipv4", "proto-ipv6", "socket-icmp", "socket-udp", "socket-tcp", "log", "verbose", "ethernet"], optional = true }
 # Optional dependencies for building examples
-[dev-dependencies]
-stm32f4xx-hal = { version = "0.8", features = ["stm32f407", "rt"] }
-cortex-m-rt = "0.6"
-cortex-m-rtic = "0.5.3"
-panic-itm = "0.4"
-log = "0.4"
+stm32f4xx-hal = { version = "0.8", optional = true }
+cortex-m = { version = "0.5", optional = true }
+cortex-m-rt = { version = "0.6", optional = true }
+cortex-m-rtic = { version = "0.5.3", optional = true }
+panic-itm = { version = "0.4", optional = true }
+log = { version = "0.4", optional = true }
+# Optional dependencies for using NAL with somltcp and cortex_m
+heapless = { version = "0.5.6", optional = true }
+embedded-nal = { version = "0.1.0", optional = true }
 
 [features]
 smoltcp-phy = ["smoltcp"]
-cortex-m-cpu = ["cortex-m"]
+smoltcp-phy-all = [
+    "smoltcp/socket-raw", "smoltcp/socket-udp", "smoltcp/socket-tcp",
+    "smoltcp/proto-ipv4", "smoltcp/proto-ipv6"
+]
+# Example-based features
+tx_stm32f407 = ["stm32f4xx-hal/stm32f407", "cortex-m", "cortex-m-rtic", "panic-itm", "log"]
+tcp_stm32f407 = ["stm32f4xx-hal/stm32f407", "cortex-m", "cortex-m-rt", "cortex-m-rtic", "smoltcp-phy-all", "smoltcp/log", "panic-itm", "log"]
+nal = [ "smoltcp-phy", "heapless", "embedded-nal", "cortex-m", "cortex-m-rtic" ]
 default = []
 
 [[example]]
 name = "tx_stm32f407"
-required-features = ["smoltcp", "cortex-m-cpu"]
+required-features = ["tx_stm32f407"]
 
 [[example]]
 name = "tcp_stm32f407"
-required-features = ["smoltcp", "cortex-m-cpu"]
+required-features = ["tcp_stm32f407"]
 
 [profile.release]
 codegen-units = 1

examples/delay.rs

@@ -0,0 +1,33 @@
+use embedded_hal::blocking::delay::{DelayMs, DelayUs};
+
+pub struct AsmDelay {
+    frequency_us: u32,
+    frequency_ms: u32,
+}
+
+impl AsmDelay {
+    pub fn new(freq: u32) -> AsmDelay {
+        AsmDelay {
+            frequency_us: (freq / 1_000_000),
+            frequency_ms: (freq / 1_000),
+        }
+    }
+}
+
+impl<U> DelayUs<U> for AsmDelay
+where
+    U: Into<u32>,
+{
+    fn delay_us(&mut self, us: U) {
+        cortex_m::asm::delay(self.frequency_us * us.into())
+    }
+}
+
+impl<U> DelayMs<U> for AsmDelay
+where
+    U: Into<u32>,
+{
+    fn delay_ms(&mut self, ms: U) {
+        cortex_m::asm::delay(self.frequency_ms * ms.into())
+    }
+}

examples/tcp_stm32f407.rs

@@ -2,31 +2,46 @@
 #![no_main]
 
 extern crate panic_itm;
-use cortex_m::{iprint, iprintln};
+use cortex_m::{iprintln, iprint};
 
-use embedded_hal::{blocking::delay::DelayMs, digital::v2::OutputPin};
-use enc424j600::smoltcp_phy;
-use stm32f4xx_hal::{
-    delay::Delay, gpio::GpioExt, rcc::RccExt, spi::Spi, stm32::ITM, time::Hertz, time::U32Ext,
+use embedded_hal::{
+    digital::v2::OutputPin,
+    blocking::delay::DelayMs
 };
+use stm32f4xx_hal::{
+    rcc::RccExt,
+    gpio::GpioExt,
+    time::U32Ext,
+    stm32::ITM,
+    delay::Delay,
+    spi::Spi,
+    time::Hertz
+};
+use enc424j600;
+use enc424j600::{smoltcp_phy, EthController};
 
-use core::fmt::Write;
-use core::str;
-use smoltcp::iface::{EthernetInterface, EthernetInterfaceBuilder, NeighborCache};
+use smoltcp::wire::{
+    EthernetAddress, IpAddress, IpCidr, Ipv6Cidr
+};
+use smoltcp::iface::{NeighborCache, EthernetInterfaceBuilder, EthernetInterface};
 use smoltcp::socket::{SocketSet, TcpSocket, TcpSocketBuffer};
-use smoltcp::wire::{EthernetAddress, IpAddress, IpCidr, Ipv6Cidr};
+use core::str;
+use core::fmt::Write;
+
+mod delay;
+use delay::AsmDelay;
 
 /// Timer
 use core::cell::RefCell;
 use cortex_m::interrupt::Mutex;
 use cortex_m_rt::exception;
-use smoltcp::time::Instant;
 use stm32f4xx_hal::{
     rcc::Clocks,
-    stm32::SYST,
     time::MilliSeconds,
-    timer::{Event as TimerEvent, Timer},
+    timer::{Timer, Event as TimerEvent},
+    stm32::SYST
 };
+use smoltcp::time::Instant;
 /// Rate in Hz
 const TIMER_RATE: u32 = 20;
 /// Interval duration in milliseconds
@@ -44,34 +59,32 @@ fn timer_setup(syst: SYST, clocks: Clocks) {
 #[exception]
 fn SysTick() {
     cortex_m::interrupt::free(|cs| {
-        *TIMER_MS.borrow(cs).borrow_mut() += TIMER_DELTA;
+        *TIMER_MS.borrow(cs)
+            .borrow_mut() += TIMER_DELTA;
     });
 }
 
 /// Obtain current time in milliseconds
 pub fn timer_now() -> MilliSeconds {
-    let ms = cortex_m::interrupt::free(|cs| *TIMER_MS.borrow(cs).borrow());
+    let ms = cortex_m::interrupt::free(|cs| {
+        *TIMER_MS.borrow(cs)
+            .borrow()
+    });
     ms.ms()
 }
 
 ///
 use stm32f4xx_hal::{
-    gpio::{
-        gpioa::{PA4, PA5, PA6, PA7},
-        Alternate, Output, PushPull, AF5,
-    },
     stm32::SPI1,
+    gpio::{
+        gpioa::{PA5, PA6, PA7, PA4},
+        Alternate, AF5, Output, PushPull
+    }
 };
-type SpiEth = enc424j600::Enc424j600<
-    Spi<
-        SPI1,
-        (
-            PA5<Alternate<AF5>>,
-            PA6<Alternate<AF5>>,
-            PA7<Alternate<AF5>>,
-        ),
-    >,
+type BoosterSpiEth = enc424j600::SpiEth<
+    Spi<SPI1, (PA5<Alternate<AF5>>, PA6<Alternate<AF5>>, PA7<Alternate<AF5>>)>,
     PA4<Output<PushPull>>,
+    AsmDelay
 >;
 
 pub struct NetStorage {
@@ -81,15 +94,19 @@ pub struct NetStorage {
 
 static mut NET_STORE: NetStorage = NetStorage {
     // Placeholder for the real IP address, which is initialized at runtime.
-    ip_addrs: [IpCidr::Ipv6(Ipv6Cidr::SOLICITED_NODE_PREFIX)],
+    ip_addrs: [IpCidr::Ipv6(
+        Ipv6Cidr::SOLICITED_NODE_PREFIX,
+    )],
     neighbor_cache: [None; 8],
 };
 
 #[rtic::app(device = stm32f4xx_hal::stm32, peripherals = true, monotonic = rtic::cyccnt::CYCCNT)]
 const APP: () = {
     struct Resources {
-        eth_iface: EthernetInterface<'static, smoltcp_phy::SmoltcpDevice<SpiEth>>,
-        itm: ITM,
+        eth_iface: EthernetInterface<
+            'static,
+            smoltcp_phy::SmoltcpDevice<BoosterSpiEth>>,
+        itm: ITM
     }
 
     #[init()]
@@ -101,23 +118,22 @@ const APP: () = {
         c.core.DWT.enable_cycle_counter();
         c.core.DCB.enable_trace();
 
-        let clocks = c
-            .device
-            .RCC
-            .constrain()
+        let clocks = c.device.RCC.constrain()
             .cfgr
             .sysclk(168.mhz())
             .hclk(168.mhz())
             .pclk1(42.mhz())
             .require_pll48clk()
             .freeze();
-        let mut delay = Delay::new(c.core.SYST, clocks);
+        let asm_delay = AsmDelay::new(clocks.sysclk().0);
+        let mut hal_delay = Delay::new(c.core.SYST, clocks);
 
         // Init ITM
         let mut itm = c.core.ITM;
         let stim0 = &mut itm.stim[0];
 
-        iprintln!(stim0, "Eth TCP Server on STM32-F407 via NIC100/ENC424J600");
+        iprintln!(stim0,
+            "Eth TCP Server on STM32-F407 via NIC100/ENC424J600");
 
         // NIC100 / ENC424J600 Set-up
         let spi1 = c.device.SPI1;
@@ -130,25 +146,22 @@ const APP: () = {
         // Map SPISEL: see Table 1, NIC100 Manual
         let mut spisel = gpioa.pa1.into_push_pull_output();
         spisel.set_high().unwrap();
-        delay.delay_ms(1_u32);
+        hal_delay.delay_ms(1_u32);
         spisel.set_low().unwrap();
 
         // Create SPI1 for HAL
         let eth_iface = {
             let mut spi_eth = {
                 let spi_eth_port = Spi::spi1(
-                    spi1,
-                    (spi1_sck, spi1_miso, spi1_mosi),
+                    spi1, (spi1_sck, spi1_miso, spi1_mosi),
                     enc424j600::spi::interfaces::SPI_MODE,
                     Hertz(enc424j600::spi::interfaces::SPI_CLOCK_FREQ),
-                    clocks,
-                );
-
-                SpiEth::new(spi_eth_port, spi1_nss).cpu_freq_mhz(168)
+                    clocks);
+                enc424j600::SpiEth::new(spi_eth_port, spi1_nss, asm_delay)
             };
 
             // Init controller
-            match spi_eth.reset(&mut delay) {
+            match spi_eth.init_dev() {
                 Ok(_) => {
                     iprintln!(stim0, "Initializing Ethernet...")
                 }
@@ -159,20 +172,20 @@ const APP: () = {
 
             // Read MAC
             let mut eth_mac_addr: [u8; 6] = [0; 6];
-            spi_eth.read_mac_addr(&mut eth_mac_addr);
+            spi_eth.read_from_mac(&mut eth_mac_addr).unwrap();
             for i in 0..6 {
                 let byte = eth_mac_addr[i];
                 match i {
                     0 => iprint!(stim0, "MAC Address = {:02x}-", byte),
                     1..=4 => iprint!(stim0, "{:02x}-", byte),
                     5 => iprint!(stim0, "{:02x}\n", byte),
-                    _ => (),
+                _ => ()
                 };
             }
 
             // Init Rx/Tx buffers
-            spi_eth.init_rxbuf();
-            spi_eth.init_txbuf();
+            spi_eth.init_rxbuf().unwrap();
+            spi_eth.init_txbuf().unwrap();
             iprintln!(stim0, "Ethernet controller initialized");
 
             // Init smoltcp interface
@@ -196,10 +209,13 @@ const APP: () = {
 
         // Setup SysTick after releasing SYST from Delay
         // Reference to stm32-eth:examples/ip.rs
-        timer_setup(delay.free(), clocks);
+        timer_setup(hal_delay.free(), clocks);
         iprintln!(stim0, "Timer initialized");
 
-        init::LateResources { eth_iface, itm }
+        init::LateResources {
+            eth_iface,
+            itm
+        }
     }
 
     #[idle(resources=[eth_iface, itm])]
@@ -229,11 +245,8 @@ const APP: () = {
         let greet_handle = socket_set.add(greet_socket);
         {
             let store = unsafe { &mut NET_STORE };
-            iprintln!(
-                stim0,
-                "TCP sockets will listen at {}",
-                store.ip_addrs[0].address()
-            );
+            iprintln!(stim0,
+                "TCP sockets will listen at {}", store.ip_addrs[0].address());
         }
 
         // Copied / modified from:
@@ -245,7 +258,8 @@ const APP: () = {
             let now = timer_now().0;
             let instant = Instant::from_millis(now as i64);
             match iface.poll(&mut socket_set, instant) {
-                Ok(_) => {}
+                Ok(_) => {
+                },
                 Err(e) => {
                     iprintln!(stim0, "[{}] Poll error: {:?}", instant, e)
                 }
@@ -254,40 +268,33 @@ const APP: () = {
             {
                 let mut socket = socket_set.get::<TcpSocket>(echo_handle);
                 if !socket.is_open() {
-                    iprintln!(
-                        stim0,
-                        "[{}] Listening to port 1234 for echoing, time-out in 10s",
-                        instant
-                    );
+                    iprintln!(stim0,
+                        "[{}] Listening to port 1234 for echoing, time-out in 10s", instant);
                     socket.listen(1234).unwrap();
                     socket.set_timeout(Some(smoltcp::time::Duration::from_millis(10000)));
                 }
                 if socket.can_recv() {
-                    iprintln!(
-                        stim0,
-                        "[{}] Received packet: {:?}",
-                        instant,
-                        socket.recv(|buffer| { (buffer.len(), str::from_utf8(buffer).unwrap()) })
-                    );
+                    iprintln!(stim0,
+                    "[{}] Received packet: {:?}", instant, socket.recv(|buffer| {
+                        (buffer.len(), str::from_utf8(buffer).unwrap())
+                    }));
                 }
             }
             // Control the "greeting" socket (:4321)
             {
                 let mut socket = socket_set.get::<TcpSocket>(greet_handle);
                 if !socket.is_open() {
-                    iprintln!(
-                        stim0,
+                    iprintln!(stim0,
                         "[{}] Listening to port 4321 for greeting, \
-                        please connect to the port",
-                        instant
-                    );
+                        please connect to the port", instant);
                     socket.listen(4321).unwrap();
                 }
 
                 if socket.can_send() {
                     let greeting = "Welcome to the server demo for STM32-F407!";
                     write!(socket, "{}\n", greeting).unwrap();
-                    iprintln!(stim0, "[{}] Greeting sent, socket closed", instant);
+                    iprintln!(stim0,
+                        "[{}] Greeting sent, socket closed", instant);
                     socket.close();
                 }
             }

examples/tx_stm32f407.rs

@@ -2,38 +2,44 @@
 #![no_main]
 
 extern crate panic_itm;
-use cortex_m::{iprint, iprintln};
+use cortex_m::{iprintln, iprint};
 
-use embedded_hal::{blocking::delay::DelayMs, digital::v2::OutputPin};
-use enc424j600::EthPhy;
-use stm32f4xx_hal::{
-    delay::Delay, gpio::GpioExt, rcc::RccExt, spi::Spi, stm32::ITM, time::Hertz, time::U32Ext,
+use embedded_hal::{
+    digital::v2::OutputPin,
+    blocking::delay::DelayMs
 };
+use stm32f4xx_hal::{
+    rcc::RccExt,
+    gpio::GpioExt,
+    time::U32Ext,
+    stm32::ITM,
+    delay::Delay,
+    spi::Spi,
+    time::Hertz
+};
+use enc424j600;
+use enc424j600::EthController;
+
+mod delay;
+use delay::AsmDelay;
 
 ///
 use stm32f4xx_hal::{
-    gpio::{
-        gpioa::{PA4, PA5, PA6, PA7},
-        Alternate, Output, PushPull, AF5,
-    },
     stm32::SPI1,
+    gpio::{
+        gpioa::{PA5, PA6, PA7, PA4},
+        Alternate, AF5, Output, PushPull
+    },
 };
-type SpiEth = enc424j600::Enc424j600<
-    Spi<
-        SPI1,
-        (
-            PA5<Alternate<AF5>>,
-            PA6<Alternate<AF5>>,
-            PA7<Alternate<AF5>>,
-        ),
-    >,
+type BoosterSpiEth = enc424j600::SpiEth<
+    Spi<SPI1, (PA5<Alternate<AF5>>, PA6<Alternate<AF5>>, PA7<Alternate<AF5>>)>,
     PA4<Output<PushPull>>,
->;
+    AsmDelay>;
 
 #[rtic::app(device = stm32f4xx_hal::stm32, peripherals = true, monotonic = rtic::cyccnt::CYCCNT)]
 const APP: () = {
     struct Resources {
-        spi_eth: SpiEth,
+        spi_eth: BoosterSpiEth,
         delay: Delay,
         itm: ITM,
     }
@@ -43,10 +49,7 @@ const APP: () = {
         c.core.SCB.enable_icache();
         c.core.SCB.enable_dcache(&mut c.core.CPUID);
 
-        let clocks = c
-            .device
-            .RCC
-            .constrain()
+        let clocks = c.device.RCC.constrain()
             .cfgr
             .sysclk(168.mhz())
             .hclk(168.mhz())
@@ -55,12 +58,14 @@ const APP: () = {
             //.pclk2(64.mhz())
             .require_pll48clk()
             .freeze();
+        let asm_delay = AsmDelay::new(clocks.sysclk().0);
         let mut delay = Delay::new(c.core.SYST, clocks);
 
         // Init ITM
         let mut itm = c.core.ITM;
         let stim0 = &mut itm.stim[0];
-        iprintln!(stim0, "Eth TX Pinging on STM32-F407 via NIC100/ENC424J600");
+        iprintln!(stim0,
+            "Eth TX Pinging on STM32-F407 via NIC100/ENC424J600");
 
         // NIC100 / ENC424J600 Set-up
         let spi1 = c.device.SPI1;
@@ -78,18 +83,15 @@ const APP: () = {
         // Create SPI1 for HAL
         let mut spi_eth = {
             let spi_eth_port = Spi::spi1(
-                spi1,
-                (spi1_sck, spi1_miso, spi1_mosi),
+                spi1, (spi1_sck, spi1_miso, spi1_mosi),
                 enc424j600::spi::interfaces::SPI_MODE,
                 Hertz(enc424j600::spi::interfaces::SPI_CLOCK_FREQ),
-                clocks,
-            );
-
-            SpiEth::new(spi_eth_port, spi1_nss).cpu_freq_mhz(168)
+                clocks);
+            enc424j600::SpiEth::new(spi_eth_port, spi1_nss, asm_delay)
         };
 
         // Init
-        match spi_eth.reset(&mut delay) {
+        match spi_eth.init_dev() {
             Ok(_) => {
                 iprintln!(stim0, "Initializing Ethernet...")
             }
@@ -100,20 +102,20 @@ const APP: () = {
 
         // Read MAC
         let mut eth_mac_addr: [u8; 6] = [0; 6];
-        spi_eth.read_mac_addr(&mut eth_mac_addr);
+        spi_eth.read_from_mac(&mut eth_mac_addr).unwrap();
         for i in 0..6 {
             let byte = eth_mac_addr[i];
             match i {
                 0 => iprint!(stim0, "MAC Address = {:02x}-", byte),
                 1..=4 => iprint!(stim0, "{:02x}-", byte),
                 5 => iprint!(stim0, "{:02x}\n", byte),
-                _ => (),
+                _ => ()
             };
         }
 
         // Init Rx/Tx buffers
-        spi_eth.init_rxbuf();
-        spi_eth.init_txbuf();
+        spi_eth.init_rxbuf().unwrap();
+        spi_eth.init_txbuf().unwrap();
         iprintln!(stim0, "Ethernet controller initialized");
 
         init::LateResources {
@@ -128,20 +130,20 @@ const APP: () = {
         let stim0 = &mut c.resources.itm.stim[0];
         // Testing Eth TX
         let eth_tx_dat: [u8; 64] = [
-            0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x08, 0x60, 0x6e, 0x44, 0x42, 0x95, 0x08, 0x06,
-            0x00, 0x01, 0x08, 0x00, 0x06, 0x04, 0x00, 0x01, 0x08, 0x60, 0x6e, 0x44, 0x42, 0x95,
-            0xc0, 0xa8, 0x01, 0x64, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xc0, 0xa8, 0x01, 0xe7,
-            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-            0x00, 0x00, 0x00, 0x00, 0x69, 0xd0, 0x85, 0x9f,
+            0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x08, 0x60,
+            0x6e, 0x44, 0x42, 0x95, 0x08, 0x06, 0x00, 0x01,
+            0x08, 0x00, 0x06, 0x04, 0x00, 0x01, 0x08, 0x60,
+            0x6e, 0x44, 0x42, 0x95, 0xc0, 0xa8, 0x01, 0x64,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xc0, 0xa8,
+            0x01, 0xe7, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+            0x00, 0x00, 0x00, 0x00, 0x69, 0xd0, 0x85, 0x9f
         ];
         loop {
             let mut eth_tx_packet = enc424j600::tx::TxPacket::new();
             eth_tx_packet.update_frame(&eth_tx_dat, 64);
-            iprint!(
-                stim0,
-                "Sending packet (len={:}): ",
-                eth_tx_packet.get_frame_length()
-            );
+            iprint!(stim0,
+                "Sending packet (len={:}): ", eth_tx_packet.get_frame_length());
             for i in 0..20 {
                 let byte = eth_tx_packet.get_frame_byte(i);
                 match i {
@@ -152,10 +154,10 @@ const APP: () = {
                     13..=14 | 16..=18 => iprint!(stim0, "{:02x}", byte),
                     5 | 11 | 15 => iprint!(stim0, "{:02x} ", byte),
                     19 => iprint!(stim0, "{:02x} ...\n", byte),
-                    _ => (),
+                    _ => ()
                 };
             }
-            c.resources.spi_eth.send_packet(&eth_tx_packet);
+            c.resources.spi_eth.send_raw_packet(&eth_tx_packet).unwrap();
             iprintln!(stim0, "Packet sent");
             c.resources.delay.delay_ms(100_u32);
         }

nix/itm-tools.nix

@@ -0,0 +1,21 @@
+{ stdenv, fetchFromGitHub, rustPlatform, pkg-config }:
+
+rustPlatform.buildRustPackage rec {
+  version = "2019-11-15";
+  pname = "itm-tools";
+
+  src = fetchFromGitHub {
+    owner = "japaric";
+    repo = "itm-tools";
+    rev = "e94155e44019d893ac8e6dab51cc282d344ab700";
+    sha256 = "19xkjym0i7y52cfhvis49c59nzvgw4906cd8bkz8ka38mbgfqgiy";
+  };
+
+  cargoPatches = [ ./itm-tools-cargo-lock.patch ];
+
+  cargoSha256 = "0is702s14pgvd5i2m8aaw3zcsshqrwj97mjgg3wikbc627pagzg7";
+
+  nativeBuildInputs = [ pkg-config ];
+
+  doCheck = false;
+}

nix/rustPlatform.nix

@@ -10,7 +10,7 @@ let
   ];
   rustChannel =
     lib.rustLib.fromManifestFile rustManifest {
-      inherit stdenv lib fetchurl patchelf;
+      inherit stdenv fetchurl patchelf;
     };
   rust =
     rustChannel.rust.override {

shell.nix

@@ -8,6 +8,8 @@ with pkgs;
 let
   rustPlatform = callPackage ./nix/rustPlatform.nix {};
 
+  itm-tools = callPackage ./nix/itm-tools.nix { inherit rustPlatform; };
+
   runHelp = writeShellScriptBin "run-help" ''
     echo "[Common Tools]"
     echo "  run-openocd-f4x"
@@ -101,7 +103,7 @@ in
 stdenv.mkDerivation {
   name = "enc424j600-stm32-env";
   buildInputs = with rustPlatform.rust; [
-    rustc cargo pkgs.gdb pkgs.openocd pkgs.tmux pkgs.itm-tools 
+    rustc cargo pkgs.gdb pkgs.openocd pkgs.tmux itm-tools 
     runHelp runTmuxEnv killTmuxEnv
     runOpenOcdF4x runItmDemuxFollow
     exTxStm32f407 exTcpStm32f407

src/lib.rs

@@ -2,7 +2,10 @@
 
 pub mod spi;
 use embedded_hal::{
-    blocking::{delay::DelayUs, spi::Transfer},
+    blocking::{
+        spi::Transfer,
+        delay::DelayUs,
+    },
     digital::v2::OutputPin,
 };
 
@@ -12,165 +15,126 @@ pub mod tx;
 #[cfg(feature="smoltcp")]
 pub mod smoltcp_phy;
 
+#[cfg(all(feature="smoltcp", feature="nal"))]
+pub mod nal;
+
 /// Max raw frame array size
 pub const RAW_FRAME_LENGTH_MAX: usize = 1518;
 
-/// Trait representing PHY layer of ENC424J600
-pub trait EthPhy {
-    fn recv_packet(&mut self, is_poll: bool) -> Result<rx::RxPacket, Error>;
-    fn send_packet(&mut self, packet: &tx::TxPacket) -> Result<(), Error>;
+pub trait EthController {
+    fn init_dev(&mut self) -> Result<(), EthControllerError>;
+    fn init_rxbuf(&mut self) -> Result<(), EthControllerError>;
+    fn init_txbuf(&mut self) -> Result<(), EthControllerError>;
+    fn receive_next(&mut self, is_poll: bool) -> Result<rx::RxPacket, EthControllerError>;
+    fn send_raw_packet(&mut self, packet: &tx::TxPacket) -> Result<(), EthControllerError>;
+    fn set_promiscuous(&mut self) -> Result<(), EthControllerError>;
+    fn read_from_mac(&mut self, mac: &mut [u8]) -> Result<(), EthControllerError>;
 }
 
 /// TODO: Improve these error types
 #[derive(Debug)]
-pub enum Error {
+pub enum EthControllerError {
     SpiPortError,
-    RegisterError,
+    GeneralError,
     // TODO: Better name?
-    NoRxPacketError,
+    NoRxPacketError
 }
 
-impl From<spi::Error> for Error {
-    fn from(_: spi::Error) -> Error {
-        Error::SpiPortError
+impl From<spi::SpiPortError> for EthControllerError {
+    fn from(_: spi::SpiPortError) -> EthControllerError {
+        EthControllerError::SpiPortError
     }
 }
 
-/// ENC424J600 controller in SPI mode
-pub struct Enc424j600<SPI: Transfer<u8>, NSS: OutputPin> {
-    spi_port: spi::SpiPort<SPI, NSS>,
+/// Ethernet controller using SPI interface
+pub struct SpiEth<SPI: Transfer<u8>,
+                  NSS: OutputPin,
+                  Delay: DelayUs<u16>> {
+    spi_port: spi::SpiPort<SPI, NSS, Delay>,
     rx_buf: rx::RxBuffer,
-    tx_buf: tx::TxBuffer,
+    tx_buf: tx::TxBuffer
 }
 
-impl<SPI: Transfer<u8>, NSS: OutputPin> Enc424j600<SPI, NSS> {
-    pub fn new(spi: SPI, nss: NSS) -> Self {
-        Enc424j600 {
-            spi_port: spi::SpiPort::new(spi, nss),
+impl <SPI: Transfer<u8>,
+      NSS: OutputPin,
+      Delay: DelayUs<u16>> SpiEth<SPI, NSS, Delay> {
+    pub fn new(spi: SPI, nss: NSS, delay: Delay) -> Self {
+        SpiEth {
+            spi_port: spi::SpiPort::new(spi, nss, delay),
             rx_buf: rx::RxBuffer::new(),
-            tx_buf: tx::TxBuffer::new(),
+            tx_buf: tx::TxBuffer::new()
+        }
     }
 }
 
-    #[cfg(feature = "cortex-m-cpu")]
-    pub fn cpu_freq_mhz(mut self, freq: u32) -> Self {
-        self.spi_port = self.spi_port.cpu_freq_mhz(freq);
-        self
-    }
-
-    pub fn init(&mut self, delay: &mut impl DelayUs<u16>) -> Result<(), Error> {
-        self.reset(delay)?;
-        self.init_rxbuf()?;
-        self.init_txbuf()?;
-        Ok(())
-    }
-
-    pub fn reset(&mut self, delay: &mut impl DelayUs<u16>) -> Result<(), Error> {
+impl <SPI: Transfer<u8>,
+      NSS: OutputPin,
+      Delay: DelayUs<u16>> EthController for SpiEth<SPI, NSS, Delay> {
+    fn init_dev(&mut self) -> Result<(), EthControllerError> {
         // Write 0x1234 to EUDAST
         self.spi_port.write_reg_16b(spi::addrs::EUDAST, 0x1234)?;
         // Verify that EUDAST is 0x1234
         let mut eudast = self.spi_port.read_reg_16b(spi::addrs::EUDAST)?;
         if eudast != 0x1234 {
-            return Err(Error::RegisterError);
+            return Err(EthControllerError::GeneralError)
         }
         // Poll CLKRDY (ESTAT<12>) to check if it is set
         loop {
             let estat = self.spi_port.read_reg_16b(spi::addrs::ESTAT)?;
-            if estat & 0x1000 == 0x1000 {
-                break;
+            if estat & 0x1000 == 0x1000 { break }
         }
-        }
-        // Issue system reset - set ETHRST (ECON2<4>) to 1
-        self.spi_port.send_opcode(spi::opcodes::SETETHRST)?;
-        delay.delay_us(25);
+        // Set ETHRST (ECON2<4>) to 1
+        let econ2 = self.spi_port.read_reg_8b(spi::addrs::ECON2)?;
+        self.spi_port.write_reg_8b(spi::addrs::ECON2, 0x10 | (econ2 & 0b11101111))?;
+        // Wait for 25us
+        self.spi_port.delay_us(25_u16);
         // Verify that EUDAST is 0x0000
         eudast = self.spi_port.read_reg_16b(spi::addrs::EUDAST)?;
         if eudast != 0x0000 {
-            return Err(Error::RegisterError);
+            return Err(EthControllerError::GeneralError)
         }
-        delay.delay_us(256);
+        // Wait for 256us
+        self.spi_port.delay_us(256_u16);
         Ok(())
     }
 
-    pub fn init_rxbuf(&mut self) -> Result<(), Error> {
+    fn init_rxbuf(&mut self) -> Result<(), EthControllerError> {
         // Set ERXST pointer
-        self.spi_port
-            .write_reg_16b(spi::addrs::ERXST, self.rx_buf.get_start_addr())?;
+        self.spi_port.write_reg_16b(spi::addrs::ERXST, self.rx_buf.get_wrap_addr())?;
         // Set ERXTAIL pointer
-        self.spi_port
-            .write_reg_16b(spi::addrs::ERXTAIL, self.rx_buf.get_tail_addr())?;
+        self.spi_port.write_reg_16b(spi::addrs::ERXTAIL, self.rx_buf.get_tail_addr())?;
         // Set MAMXFL to maximum number of bytes in each accepted packet
-        self.spi_port
-            .write_reg_16b(spi::addrs::MAMXFL, RAW_FRAME_LENGTH_MAX as u16)?;
-        // Enable RX - set RXEN (ECON1<0>) to 1
-        self.spi_port.send_opcode(spi::opcodes::ENABLERX)?;
+        self.spi_port.write_reg_16b(spi::addrs::MAMXFL, RAW_FRAME_LENGTH_MAX as u16)?;
+        // Enable RXEN (ECON1<0>)
+        let econ1 = self.spi_port.read_reg_16b(spi::addrs::ECON1)?;
+        self.spi_port.write_reg_16b(spi::addrs::ECON1, 0x1 | (econ1 & 0xfffe))?;
         Ok(())
     }
 
-    pub fn init_txbuf(&mut self) -> Result<(), Error> {
+    fn init_txbuf(&mut self) -> Result<(), EthControllerError> {
         // Set EGPWRPT pointer
         self.spi_port.write_reg_16b(spi::addrs::EGPWRPT, 0x0000)?;
         Ok(())
     }
 
-    /// Set controller to Promiscuous Mode
-    pub fn set_promiscuous(&mut self) -> Result<(), Error> {
-        // From Section 10.12, ENC424J600 Data Sheet:
-        // "To accept all incoming frames regardless of content (Promiscuous mode),
-        // set the CRCEN, RUNTEN, UCEN, NOTMEEN and MCEN bits."
-        let erxfcon_lo = self.spi_port.read_reg_8b(spi::addrs::ERXFCON)?;
-        self.spi_port.write_reg_8b(
-            spi::addrs::ERXFCON,
-            0b0101_1110 | (erxfcon_lo & 0b1010_0001),
-        )?;
-        Ok(())
-    }
-
-    /// Read MAC to [u8; 6]
-    pub fn read_mac_addr(&mut self, mac: &mut [u8]) -> Result<(), Error> {
-        mac[0] = self.spi_port.read_reg_8b(spi::addrs::MAADR1)?;
-        mac[1] = self.spi_port.read_reg_8b(spi::addrs::MAADR1 + 1)?;
-        mac[2] = self.spi_port.read_reg_8b(spi::addrs::MAADR2)?;
-        mac[3] = self.spi_port.read_reg_8b(spi::addrs::MAADR2 + 1)?;
-        mac[4] = self.spi_port.read_reg_8b(spi::addrs::MAADR3)?;
-        mac[5] = self.spi_port.read_reg_8b(spi::addrs::MAADR3 + 1)?;
-        Ok(())
-    }
-
-    pub fn write_mac_addr(&mut self, mac: &[u8]) -> Result<(), Error> {
-        self.spi_port.write_reg_8b(spi::addrs::MAADR1, mac[0])?;
-        self.spi_port.write_reg_8b(spi::addrs::MAADR1 + 1, mac[1])?;
-        self.spi_port.write_reg_8b(spi::addrs::MAADR2, mac[2])?;
-        self.spi_port.write_reg_8b(spi::addrs::MAADR2 + 1, mac[3])?;
-        self.spi_port.write_reg_8b(spi::addrs::MAADR3, mac[4])?;
-        self.spi_port.write_reg_8b(spi::addrs::MAADR3 + 1, mac[5])?;
-        Ok(())
-    }
-}
-
-impl<SPI: Transfer<u8>, NSS: OutputPin> EthPhy for Enc424j600<SPI, NSS> {
     /// Receive the next packet and return it
     /// Set is_poll to true for returning until PKTIF is set;
     /// Set is_poll to false for returning Err when PKTIF is not set
-    fn recv_packet(&mut self, is_poll: bool) -> Result<rx::RxPacket, Error> {
+    fn receive_next(&mut self, is_poll: bool) -> Result<rx::RxPacket, EthControllerError> {
         // Poll PKTIF (EIR<4>) to check if it is set
         loop {
             let eir = self.spi_port.read_reg_16b(spi::addrs::EIR)?;
-            if eir & 0x40 == 0x40 {
-                break;
-            }
+            if eir & 0x40 == 0x40 { break }
             if !is_poll {
-                return Err(Error::NoRxPacketError);
+                return Err(EthControllerError::NoRxPacketError)
             }
         }
         // Set ERXRDPT pointer to next_addr
-        self.spi_port
-            .write_reg_16b(spi::addrs::ERXRDPT, self.rx_buf.get_next_addr())?;
+        self.spi_port.write_reg_16b(spi::addrs::ERXRDPT, self.rx_buf.get_next_addr())?;
         // Read 2 bytes to update next_addr
         let mut next_addr_buf = [0; 3];
         self.spi_port.read_rxdat(&mut next_addr_buf, 2)?;
-        self.rx_buf
-            .set_next_addr((next_addr_buf[1] as u16) | ((next_addr_buf[2] as u16) << 8));
+        self.rx_buf.set_next_addr((next_addr_buf[1] as u16) | ((next_addr_buf[2] as u16) << 8));
         // Read 6 bytes to update rsv
         let mut rsv_buf = [0; 7];
         self.spi_port.read_rxdat(&mut rsv_buf, 6)?;
@@ -182,61 +146,68 @@ impl<SPI: Transfer<u8>, NSS: OutputPin> EthPhy for Enc424j600<SPI, NSS> {
         rx_packet.update_frame_length();
         // Read frame bytes
         let mut frame_buf = [0; RAW_FRAME_LENGTH_MAX];
-        self.spi_port
-            .read_rxdat(&mut frame_buf, rx_packet.get_frame_length())?;
+        self.spi_port.read_rxdat(&mut frame_buf, rx_packet.get_frame_length())?;
         rx_packet.copy_frame_from(&frame_buf[1..]);
         // Set ERXTAIL pointer to (next_addr - 2)
-        // * Assume head, tail, next and wrap addresses are word-aligned (even)
-        // - If next_addr is at least (start_addr+2), then set tail pointer to the word right before next_addr
-        if self.rx_buf.get_next_addr() > self.rx_buf.get_start_addr() {
-            self.spi_port
-                .write_reg_16b(spi::addrs::ERXTAIL, self.rx_buf.get_next_addr() - 2)?;
-        // - Otherwise, next_addr will wrap, so set tail pointer to the last word address of RX buffer
+        if self.rx_buf.get_next_addr() > rx::ERXST_DEFAULT {
+            self.spi_port.write_reg_16b(spi::addrs::ERXTAIL, self.rx_buf.get_next_addr() - 2)?;
         } else {
-            self.spi_port
-                .write_reg_16b(spi::addrs::ERXTAIL, rx::RX_MAX_ADDRESS - 1)?;
+            self.spi_port.write_reg_16b(spi::addrs::ERXTAIL, rx::RX_MAX_ADDRESS - 1)?;
         }
-        // Decrement PKTCNT - set PKTDEC (ECON1<8>)
-        self.spi_port.send_opcode(spi::opcodes::SETPKTDEC)?;
+        // Set PKTDEC (ECON1<88>) to decrement PKTCNT
+        let econ1_hi = self.spi_port.read_reg_8b(spi::addrs::ECON1 + 1)?;
+        self.spi_port.write_reg_8b(spi::addrs::ECON1 + 1, 0x01 | (econ1_hi & 0xfe))?;
         // Return the RxPacket
         Ok(rx_packet)
     }
 
     /// Send an established packet
-    fn send_packet(&mut self, packet: &tx::TxPacket) -> Result<(), Error> {
+    fn send_raw_packet(&mut self, packet: &tx::TxPacket) -> Result<(), EthControllerError> {
         // Set EGPWRPT pointer to next_addr
-        self.spi_port
-            .write_reg_16b(spi::addrs::EGPWRPT, self.tx_buf.get_next_addr())?;
+        self.spi_port.write_reg_16b(spi::addrs::EGPWRPT, self.tx_buf.get_next_addr())?;
         // Copy packet data to SRAM Buffer
         // 1-byte Opcode is included
         let mut txdat_buf: [u8; RAW_FRAME_LENGTH_MAX + 1] = [0; RAW_FRAME_LENGTH_MAX + 1];
         packet.write_frame_to(&mut txdat_buf[1..]);
-        self.spi_port
-            .write_txdat(&mut txdat_buf, packet.get_frame_length())?;
+        self.spi_port.write_txdat(&mut txdat_buf, packet.get_frame_length())?;
         // Set ETXST to packet start address
-        self.spi_port
-            .write_reg_16b(spi::addrs::ETXST, self.tx_buf.get_next_addr())?;
+        self.spi_port.write_reg_16b(spi::addrs::ETXST, self.tx_buf.get_next_addr())?;
         // Set ETXLEN to packet length
-        self.spi_port
-            .write_reg_16b(spi::addrs::ETXLEN, packet.get_frame_length() as u16)?;
-        // Send packet - set TXRTS (ECON1<1>) to start transmission
-        self.spi_port.send_opcode(spi::opcodes::SETTXRTS)?;
+        self.spi_port.write_reg_16b(spi::addrs::ETXLEN, packet.get_frame_length() as u16)?;
+        // Set TXRTS (ECON1<1>) to start transmission
+        let mut econ1_lo = self.spi_port.read_reg_8b(spi::addrs::ECON1)?;
+        self.spi_port.write_reg_8b(spi::addrs::ECON1, 0x02 | (econ1_lo & 0xfd))?;
         // Poll TXRTS (ECON1<1>) to check if it is reset
         loop {
-            let econ1_lo = self.spi_port.read_reg_8b(spi::addrs::ECON1)?;
-            if econ1_lo & 0x02 == 0 {
-                break;
-            }
+            econ1_lo = self.spi_port.read_reg_8b(spi::addrs::ECON1)?;
+            if econ1_lo & 0x02 == 0 { break }
         }
         // TODO: Read ETXSTAT to understand Ethernet transmission status
         // (See: Register 9-2, ENC424J600 Data Sheet)
         // Update TX buffer start address
-        // * Assume TX buffer consumes the entire general-purpose SRAM block
-        self.tx_buf.set_next_addr(
-            (self.tx_buf.get_next_addr() + packet.get_frame_length() as u16)
-                % self.rx_buf.get_start_addr()
-                - self.tx_buf.get_start_addr(),
-        );
+        self.tx_buf.set_next_addr((self.tx_buf.get_next_addr() + packet.get_frame_length() as u16) %
+            tx::GPBUFEN_DEFAULT);
+        Ok(())
+    }
+
+    /// Set controller to Promiscuous Mode
+    fn set_promiscuous(&mut self) -> Result<(), EthControllerError> {
+        // From Section 10.12, ENC424J600 Data Sheet:
+        // "To accept all incoming frames regardless of content (Promiscuous mode),
+        // set the CRCEN, RUNTEN, UCEN, NOTMEEN and MCEN bits."
+        let erxfcon_lo = self.spi_port.read_reg_8b(spi::addrs::ERXFCON)?;
+        self.spi_port.write_reg_8b(spi::addrs::ERXFCON, 0b0101_1110 | (erxfcon_lo & 0b1010_0001))?;
+        Ok(())
+    }
+
+    /// Read MAC to [u8; 6]
+    fn read_from_mac(&mut self, mac: &mut [u8]) -> Result<(), EthControllerError> {
+        mac[0] = self.spi_port.read_reg_8b(spi::addrs::MAADR1)?;
+        mac[1] = self.spi_port.read_reg_8b(spi::addrs::MAADR1 + 1)?;
+        mac[2] = self.spi_port.read_reg_8b(spi::addrs::MAADR2)?;
+        mac[3] = self.spi_port.read_reg_8b(spi::addrs::MAADR2 + 1)?;
+        mac[4] = self.spi_port.read_reg_8b(spi::addrs::MAADR3)?;
+        mac[5] = self.spi_port.read_reg_8b(spi::addrs::MAADR3 + 1)?;
         Ok(())
     }
 }

src/nal.rs

@@ -0,0 +1,265 @@
+use core::cell::RefCell;
+use heapless::{consts, Vec};
+use embedded_nal as nal;
+use nal::nb;
+use smoltcp as net;
+use embedded_hal::{
+    blocking::spi::Transfer,
+    blocking::delay::DelayUs,
+    digital::v2::OutputPin
+};
+use rtic::cyccnt::Instant;
+
+
+#[derive(Debug)]
+pub enum NetworkError {
+    NoSocket,
+    ConnectionFailure,
+    ReadFailure,
+    WriteFailure,
+    Unsupported,
+}
+
+pub type NetworkInterface<SPI, NSS, Delay> = net::iface::EthernetInterface<
+    'static,
+    crate::smoltcp_phy::SmoltcpDevice<
+        crate::SpiEth<SPI, NSS, Delay>
+    >,
+>;
+
+pub struct NetworkStack<'a, SPI, NSS, Delay>
+where
+    SPI: 'static + Transfer<u8>,
+    NSS: 'static + OutputPin,
+    Delay: 'static + DelayUs<u16>
+{
+    network_interface: RefCell<NetworkInterface<SPI, NSS, Delay>>,
+    sockets: RefCell<net::socket::SocketSet<'a>>,
+    next_port: RefCell<u16>,
+    unused_handles: RefCell<Vec<net::socket::SocketHandle, consts::U16>>,
+    time_ms: RefCell<u32>,
+    last_update_instant: RefCell<Option<Instant>>,
+}
+
+impl<'a, SPI, NSS, Delay> NetworkStack<'a, SPI, NSS, Delay>
+where
+    SPI: Transfer<u8>,
+    NSS: OutputPin,
+    Delay: DelayUs<u16>
+{
+    pub fn new(interface: NetworkInterface<SPI, NSS, Delay>, sockets: net::socket::SocketSet<'a>) -> Self {
+        let mut unused_handles: Vec<net::socket::SocketHandle, consts::U16> = Vec::new();
+        for socket in sockets.iter() {
+            unused_handles.push(socket.handle()).unwrap();
+        }
+
+        NetworkStack {
+            network_interface: RefCell::new(interface),
+            sockets: RefCell::new(sockets),
+            next_port: RefCell::new(49152),
+            unused_handles: RefCell::new(unused_handles),
+            time_ms: RefCell::new(0),
+            last_update_instant: RefCell::new(None),
+        }
+    }
+
+    // Include auto_time_update to allow Instant::now() to not be called
+    // Instant::now() is not safe to call in `init()` context
+    pub fn update(&self, auto_time_update: bool) -> bool {
+        if auto_time_update {
+            // Check if it is the first time the stack has updated the time itself
+            let now = match *self.last_update_instant.borrow() {
+                // If it is the first time, do not advance time
+                // Simply store the current instant to initiate time updating
+                None => Instant::now(),
+
+                // If it was updated before, advance time and update last_update_instant
+                Some(instant) => {
+                    // Calculate elapsed time
+                    let now = Instant::now();
+                    let duration = now.duration_since(instant);
+                    // Adjust duration into ms (note: decimal point truncated)
+                    self.advance_time(duration.as_cycles() / 168_000);
+                    now
+                }
+            };
+
+            self.last_update_instant.replace(Some(now));
+        }
+
+        match self.network_interface.borrow_mut().poll(
+            &mut self.sockets.borrow_mut(),
+            net::time::Instant::from_millis(*self.time_ms.borrow() as i64),
+        ) {
+            Ok(changed) => changed == false,
+            Err(_e) => {
+                true
+            }
+        }
+    }
+
+    pub fn advance_time(&self, duration: u32) {
+        *self.time_ms.borrow_mut() += duration;
+    }
+
+    fn get_ephemeral_port(&self) -> u16 {
+        // Get the next ephemeral port
+        let current_port = self.next_port.borrow().clone();
+
+        let (next, wrap) = self.next_port.borrow().overflowing_add(1);
+        *self.next_port.borrow_mut() = if wrap { 49152 } else { next };
+
+        return current_port;
+    }
+}
+
+impl<'a, SPI, NSS, Delay> nal::TcpStack for NetworkStack<'a, SPI, NSS, Delay>
+where
+    SPI: Transfer<u8>,
+    NSS: OutputPin,
+    Delay: DelayUs<u16>
+{
+    type TcpSocket = net::socket::SocketHandle;
+    type Error = NetworkError;
+
+    fn open(&self, _mode: nal::Mode) -> Result<Self::TcpSocket, Self::Error> {
+        match self.unused_handles.borrow_mut().pop() {
+            Some(handle) => {
+                // Abort any active connections on the handle.
+                let mut sockets = self.sockets.borrow_mut();
+                let internal_socket: &mut net::socket::TcpSocket = &mut *sockets.get(handle);
+                internal_socket.abort();
+
+                Ok(handle)
+            }
+            None => Err(NetworkError::NoSocket),
+        }
+    }
+
+    // Ideally connect is only to be performed in `init()` of `main.rs`
+    // Calling `Instant::now()` of `rtic::cyccnt` would face correctness issue during `init()`
+    fn connect(
+        &self,
+        socket: Self::TcpSocket,
+        remote: nal::SocketAddr,
+    ) -> Result<Self::TcpSocket, Self::Error> {
+        let address = {
+            let mut sockets = self.sockets.borrow_mut();
+            let internal_socket: &mut net::socket::TcpSocket = &mut *sockets.get(socket);
+
+            // If we're already in the process of connecting, ignore the request silently.
+            if internal_socket.is_open() {
+                return Ok(socket);
+            }
+
+            match remote.ip() {
+                nal::IpAddr::V4(addr) => {
+                    let octets = addr.octets();
+                    let address =
+                        net::wire::Ipv4Address::new(octets[0], octets[1], octets[2], octets[3]);
+                    internal_socket
+                        .connect((address, remote.port()), self.get_ephemeral_port())
+                        .map_err(|_| NetworkError::ConnectionFailure)?;
+                    address
+                }
+                nal::IpAddr::V6(_) => {
+                    // Match W5500 behavior: Reject the use of IPV6
+                    return Err(NetworkError::Unsupported);
+                }
+            }
+        };
+
+        // Match W5500 behavior: Poll until connected
+        loop {
+            match self.is_connected(&socket) {
+                Ok(true) => break,
+                _ => {
+                    let mut sockets = self.sockets.borrow_mut();
+                    let internal_socket: &mut net::socket::TcpSocket = &mut *sockets.get(socket);
+                    // If the connect got ACK->RST, it will end up in Closed TCP state
+                    // Perform reconnection in this case
+                    // In all other scenario, simply wait for TCP connection to be established
+                    if internal_socket.state() == net::socket::TcpState::Closed {
+                        internal_socket.close();
+                        internal_socket
+                            .connect((address, remote.port()), self.get_ephemeral_port())
+                            .map_err(|_| NetworkError::ConnectionFailure)?;
+                    }
+                }
+            }
+
+            // Avoid using Instant::now() and Advance time manually
+            self.update(false);
+
+            // Delay for 1 ms, minimum time unit of smoltcp
+            // TODO: Allow clock configuration, if supported in main
+            cortex_m::asm::delay(168_000_000 / 1_000);
+            {
+                self.advance_time(1);
+            }
+        }
+
+        Ok(socket)
+    }
+
+    fn is_connected(&self, socket: &Self::TcpSocket) -> Result<bool, Self::Error> {
+        let mut sockets = self.sockets.borrow_mut();
+        let socket: &mut net::socket::TcpSocket = &mut *sockets.get(*socket);
+
+        Ok(socket.may_send() && socket.may_recv())
+    }
+
+    fn write(&self, socket: &mut Self::TcpSocket, buffer: &[u8]) -> nb::Result<usize, Self::Error> {
+        let mut non_queued_bytes = &buffer[..];
+        while non_queued_bytes.len() != 0 {
+            let result = {
+                let mut sockets = self.sockets.borrow_mut();
+                let socket: &mut net::socket::TcpSocket = &mut *sockets.get(*socket);
+                let result = socket.send_slice(non_queued_bytes);
+                result
+            };
+
+            match result {
+                Ok(num_bytes) => {
+                    // In case the buffer is filled up, push bytes into ethernet driver
+                    if num_bytes != non_queued_bytes.len() {
+                        self.update(true);
+                    }
+
+                    // Process the unwritten bytes again, if any
+                    non_queued_bytes = &non_queued_bytes[num_bytes..]
+                }
+                Err(_) => return Err(nb::Error::Other(NetworkError::WriteFailure)),
+            }
+        }
+
+        Ok(buffer.len())
+    }
+
+    fn read(
+        &self,
+        socket: &mut Self::TcpSocket,
+        buffer: &mut [u8],
+    ) -> nb::Result<usize, Self::Error> {
+        // Enqueue received bytes into the TCP socket buffer
+        self.update(true);
+
+        let mut sockets = self.sockets.borrow_mut();
+        let socket: &mut net::socket::TcpSocket = &mut *sockets.get(*socket);
+
+        let result = socket.recv_slice(buffer);
+        match result {
+            Ok(num_bytes) => Ok(num_bytes),
+            Err(_) => Err(nb::Error::Other(NetworkError::ReadFailure)),
+        }
+    }
+
+    fn close(&self, socket: Self::TcpSocket) -> Result<(), Self::Error> {
+        let mut sockets = self.sockets.borrow_mut();
+        let internal_socket: &mut net::socket::TcpSocket = &mut *sockets.get(socket);
+        internal_socket.close();
+
+        self.unused_handles.borrow_mut().push(socket).unwrap();
+        Ok(())
+    }
+}

src/rx.rs

@@ -11,25 +11,25 @@ pub const RSV_LENGTH: usize = 6;
 /// Struct for RX Buffer on the hardware
 /// TODO: Should be a singleton
 pub struct RxBuffer {
-    start_addr: u16,
+    wrap_addr: u16,
     next_addr: u16,
-    tail_addr: u16,
+    tail_addr: u16
 }
 
 impl RxBuffer {
     pub fn new() -> Self {
         RxBuffer {
-            start_addr: ERXST_DEFAULT,
+            wrap_addr: ERXST_DEFAULT,
             next_addr: ERXST_DEFAULT,
-            tail_addr: ERXTAIL_DEFAULT,
+            tail_addr: ERXTAIL_DEFAULT
         }
     }
 
-    pub fn set_start_addr(&mut self, addr: u16) {
-        self.start_addr = addr;
+    pub fn set_wrap_addr(&mut self, addr: u16) {
+        self.wrap_addr = addr;
     }
-    pub fn get_start_addr(&self) -> u16 {
-        self.start_addr
+    pub fn get_wrap_addr(& self) -> u16{
+        self.wrap_addr
     }
 
     pub fn set_next_addr(&mut self, addr: u16) {
@@ -52,7 +52,7 @@ impl RxBuffer {
 pub struct RxPacket {
     rsv: Rsv,
     frame: [u8; RAW_FRAME_LENGTH_MAX],
-    frame_length: usize,
+    frame_length: usize
 }
 
 impl RxPacket {
@@ -60,7 +60,7 @@ impl RxPacket {
         RxPacket {
             rsv: Rsv::new(),
             frame: [0; RAW_FRAME_LENGTH_MAX],
-            frame_length: 0,
+            frame_length: 0
         }
     }
 
@@ -106,14 +106,14 @@ impl RxPacket {
 struct Rsv {
     raw_rsv: [u8; RSV_LENGTH],
     // TODO: Add more definitions
-    frame_length: u16,
+    frame_length: u16
 }
 
 impl Rsv {
     fn new() -> Self {
         Rsv {
             raw_rsv: [0; RSV_LENGTH],
-            frame_length: 0_u16,
+            frame_length: 0_u16
         }
     }
 

src/smoltcp_phy.rs

@@ -1,30 +1,32 @@
-use crate::{tx, EthPhy, RAW_FRAME_LENGTH_MAX};
+use crate::{
+    EthController, tx, RAW_FRAME_LENGTH_MAX
+};
 use core::cell;
 use smoltcp::{
     phy::{Device, DeviceCapabilities, RxToken, TxToken},
     time::Instant,
-    Error,
+    Error
 };
 
-pub struct SmoltcpDevice<E: EthPhy> {
-    pub eth_phy: cell::RefCell<E>,
+pub struct SmoltcpDevice<EC: EthController> {
+    pub eth_controller: cell::RefCell<EC>,
     rx_packet_buf: [u8; RAW_FRAME_LENGTH_MAX],
-    tx_packet_buf: [u8; RAW_FRAME_LENGTH_MAX],
+    tx_packet_buf: [u8; RAW_FRAME_LENGTH_MAX]
 }
 
-impl<E: EthPhy> SmoltcpDevice<E> {
-    pub fn new(eth_phy: E) -> Self {
+impl<EC: EthController> SmoltcpDevice<EC> {
+    pub fn new(eth_controller: EC) -> Self {
         SmoltcpDevice {
-            eth_phy: cell::RefCell::new(eth_phy),
+            eth_controller: cell::RefCell::new(eth_controller),
             rx_packet_buf: [0; RAW_FRAME_LENGTH_MAX],
-            tx_packet_buf: [0; RAW_FRAME_LENGTH_MAX],
+            tx_packet_buf: [0; RAW_FRAME_LENGTH_MAX]
         }
     }
 }
 
-impl<'a, E: 'a + EthPhy> Device<'a> for SmoltcpDevice<E> {
+impl<'a, EC: 'a + EthController> Device<'a> for SmoltcpDevice<EC> {
     type RxToken = EthRxToken<'a>;
-    type TxToken = EthTxToken<'a, E>;
+    type TxToken = EthTxToken<'a, EC>;
 
     fn capabilities(&self) -> DeviceCapabilities {
         let mut caps = DeviceCapabilities::default();
@@ -33,33 +35,33 @@ impl<'a, E: 'a + EthPhy> Device<'a> for SmoltcpDevice<E> {
     }
 
     fn receive(&'a mut self) -> Option<(Self::RxToken, Self::TxToken)> {
-        let self_p = (&mut *self) as *mut SmoltcpDevice<E>;
-        match self.eth_phy.borrow_mut().recv_packet(false) {
+        let self_p = (&mut *self) as *mut SmoltcpDevice<EC>;
+        match self.eth_controller.borrow_mut().receive_next(false) {
             Ok(rx_packet) => {
                 // Write received packet to RX packet buffer
                 rx_packet.write_frame_to(&mut self.rx_packet_buf);
                 // Construct a RxToken
                 let rx_token = EthRxToken {
                     buf: &mut self.rx_packet_buf,
-                    len: rx_packet.get_frame_length(),
+                    len: rx_packet.get_frame_length()
                 };
                 // Construct a blank TxToken
                 let tx_token = EthTxToken {
                     buf: &mut self.tx_packet_buf,
-                    dev: self_p,
+                    dev: self_p
                 };
                 Some((rx_token, tx_token))
-            }
-            Err(_) => None,
+            },
+            Err(_) => None
         }
     }
 
     fn transmit(&'a mut self) -> Option<Self::TxToken> {
-        let self_p = (&mut *self) as *mut SmoltcpDevice<E>;
+        let self_p = (&mut *self) as *mut SmoltcpDevice<EC>;
         // Construct a blank TxToken
         let tx_token = EthTxToken {
             buf: &mut self.tx_packet_buf,
-            dev: self_p,
+            dev: self_p
         };
         Some(tx_token)
     }
@@ -67,7 +69,7 @@ impl<'a, E: 'a + EthPhy> Device<'a> for SmoltcpDevice<E> {
 
 pub struct EthRxToken<'a> {
     buf: &'a mut [u8],
-    len: usize,
+    len: usize
 }
 
 impl<'a> RxToken for EthRxToken<'a> {
@@ -79,12 +81,12 @@ impl<'a> RxToken for EthRxToken<'a> {
     }
 }
 
-pub struct EthTxToken<'a, E: EthPhy> {
+pub struct EthTxToken<'a, EC: EthController> {
     buf: &'a mut [u8],
-    dev: *mut SmoltcpDevice<E>,
+    dev: *mut SmoltcpDevice<EC>
 }
 
-impl<'a, E: 'a + EthPhy> TxToken for EthTxToken<'a, E> {
+impl<'a, EC: 'a + EthController> TxToken for EthTxToken<'a, EC> {
     fn consume<R, F>(self, _timestamp: Instant, len: usize, f: F) -> Result<R, Error>
     where
         F: FnOnce(&mut [u8]) -> Result<R, Error>,
@@ -95,10 +97,12 @@ impl<'a, E: 'a + EthPhy> TxToken for EthTxToken<'a, E> {
         // Update frame length and write frame bytes
         tx_packet.update_frame(&mut self.buf[..len], len);
         // Send the packet as raw
-        let eth_phy = unsafe { &mut (*self.dev).eth_phy };
-        match eth_phy.borrow_mut().send_packet(&tx_packet) {
-            Ok(_) => result,
-            Err(_) => Err(Error::Exhausted),
+        let eth_controller = unsafe {
+            &mut (*self.dev).eth_controller
+        };
+        match eth_controller.borrow_mut().send_raw_packet(&tx_packet) {
+            Ok(_) => { result },
+            Err(_) => Err(Error::Exhausted)
         }
     }
 }

src/spi.rs

@@ -1,4 +1,7 @@
-use embedded_hal::{blocking::spi::Transfer, digital::v2::OutputPin};
+use embedded_hal::{
+    blocking::{spi::Transfer, delay::DelayUs},
+    digital::v2::OutputPin,
+};
 
 pub mod interfaces {
     use embedded_hal::spi;
@@ -12,21 +15,11 @@ pub mod interfaces {
 }
 
 pub mod opcodes {
-    /// 1-byte Instructions
-    pub const SETETHRST: u8 = 0b1100_1010;
-    pub const SETPKTDEC: u8 = 0b1100_1100;
-    pub const SETTXRTS: u8 = 0b1101_0100;
-    pub const ENABLERX: u8 = 0b1110_1000;
-    /// 3-byte Instructions
-    pub const WRXRDPT: u8 = 0b0110_0100; // 8-bit opcode followed by data
-    pub const RRXRDPT: u8 = 0b0110_0110; // 8-bit opcode followed by data
-    pub const WGPWRPT: u8 = 0b0110_1100; // 8-bit opcode followed by data
-    pub const RGPWRPT: u8 = 0b0110_1110; // 8-bit opcode followed by data
-    /// N-byte Instructions
+    /// SPI Opcodes
     pub const RCRU: u8 = 0b0010_0000;
     pub const WCRU: u8 = 0b0010_0010;
-    pub const RRXDATA: u8 = 0b0010_1100; // 8-bit opcode followed by data
-    pub const WGPDATA: u8 = 0b0010_1010; // 8-bit opcode followed by data
+    pub const RERXDATA: u8 = 0b0010_1100;   // 8-bit opcode followed by data
+    pub const WEGPDATA: u8 = 0b0010_1010;   // 8-bit opcode followed by data
 }
 
 pub mod addrs {
@@ -58,160 +51,157 @@ pub mod addrs {
 
 /// Struct for SPI I/O interface on ENC424J600
 /// Note: stm32f4xx_hal::spi's pins include: SCK, MISO, MOSI
-pub struct SpiPort<SPI: Transfer<u8>, NSS: OutputPin> {
+pub struct SpiPort<SPI: Transfer<u8>,
+                   NSS: OutputPin,
+                   Delay: DelayUs<u16>> {
     spi: SPI,
     nss: NSS,
-    #[cfg(feature = "cortex-m-cpu")]
-    cpu_freq_mhz: f32,
+    delay: Delay,
 }
 
-pub enum Error {
-    OpcodeError,
-    TransferError,
+pub enum SpiPortError {
+    TransferError
 }
 
 #[allow(unused_must_use)]
-impl<SPI: Transfer<u8>, NSS: OutputPin> SpiPort<SPI, NSS> {
+impl <SPI: Transfer<u8>,
+      NSS: OutputPin,
+      Delay: DelayUs<u16>> SpiPort<SPI, NSS, Delay> {
     // TODO: return as Result()
-    pub fn new(spi: SPI, mut nss: NSS) -> Self {
+    pub fn new(spi: SPI, mut nss: NSS, delay: Delay) -> Self {
         nss.set_high();
 
         SpiPort {
             spi,
             nss,
-            #[cfg(feature = "cortex-m-cpu")]
-            cpu_freq_mhz: 0.,
+            delay
         }
     }
 
-    #[cfg(feature = "cortex-m-cpu")]
-    pub fn cpu_freq_mhz(mut self, freq: u32) -> Self {
-        self.cpu_freq_mhz = freq as f32;
-        self
-    }
-
-    pub fn read_reg_8b(&mut self, addr: u8) -> Result<u8, Error> {
+    pub fn read_reg_8b(&mut self, addr: u8) -> Result<u8, SpiPortError> {
         // Using RCRU instruction to read using unbanked (full) address
-        let mut buf: [u8; 4] = [0; 4];
-        buf[1] = addr;
-        self.rw_n(&mut buf, opcodes::RCRU, 2)?;
-        Ok(buf[2])
+        let r_data = self.rw_addr_u8(opcodes::RCRU, addr, 0)?;
+        Ok(r_data)
     }
 
-    pub fn read_reg_16b(&mut self, lo_addr: u8) -> Result<u16, Error> {
-        // Unless the register can be written with specific opcode,
-        // use WCRU instruction to write using unbanked (full) address
-        let mut buf: [u8; 4] = [0; 4];
-        let mut data_offset = 0; // number of bytes separating
-                                 // actual data from opcode
-        match lo_addr {
-            addrs::ERXRDPT | addrs::EGPWRPT => {}
-            _ => {
-                buf[1] = lo_addr;
-                data_offset = 1;
-            }
-        }
-        self.rw_n(
-            &mut buf,
-            match lo_addr {
-                addrs::ERXRDPT => opcodes::RRXRDPT,
-                addrs::EGPWRPT => opcodes::RGPWRPT,
-                _ => opcodes::RCRU,
-            },
-            2 + data_offset, // extra 8-bit lo_addr before data
-        )?;
-        Ok(buf[data_offset + 1] as u16 | (buf[data_offset + 2] as u16) << 8)
+    pub fn read_reg_16b(&mut self, lo_addr: u8) -> Result<u16, SpiPortError> {
+        let r_data_lo = self.read_reg_8b(lo_addr)?;
+        let r_data_hi = self.read_reg_8b(lo_addr + 1)?;
+        // Combine top and bottom 8-bit to return 16-bit
+        Ok(((r_data_hi as u16) << 8) | r_data_lo as u16)
     }
 
     // Currently requires manual slicing (buf[1..]) for the data read back
-    pub fn read_rxdat<'a>(&mut self, buf: &'a mut [u8], data_length: usize) -> Result<(), Error> {
-        self.rw_n(buf, opcodes::RRXDATA, data_length)
+    pub fn read_rxdat<'a>(&mut self, buf: &'a mut [u8], data_length: usize)
+                         -> Result<(), SpiPortError> {
+        let r_valid = self.r_n(buf, opcodes::RERXDATA, data_length)?;
+        Ok(r_valid)
     }
 
-    // Currently requires actual data to be stored in buf[1..] instead of buf[0..]
+    // Currenly requires actual data to be stored in buf[1..] instead of buf[0..]
     // TODO: Maybe better naming?
-    pub fn write_txdat<'a>(&mut self, buf: &'a mut [u8], data_length: usize) -> Result<(), Error> {
-        self.rw_n(buf, opcodes::WGPDATA, data_length)
+    pub fn write_txdat<'a>(&mut self, buf: &'a mut [u8], data_length: usize)
+                          -> Result<(), SpiPortError> {
+        let w_valid = self.w_n(buf, opcodes::WEGPDATA, data_length)?;
+        Ok(w_valid)
     }
 
-    pub fn write_reg_8b(&mut self, addr: u8, data: u8) -> Result<(), Error> {
+    pub fn write_reg_8b(&mut self, addr: u8, data: u8) -> Result<(), SpiPortError> {
+        // TODO: addr should be separated from w_data
         // Using WCRU instruction to write using unbanked (full) address
-        let mut buf: [u8; 3] = [0; 3];
-        buf[1] = addr;
-        buf[2] = data;
-        self.rw_n(&mut buf, opcodes::WCRU, 2)
+        self.rw_addr_u8(opcodes::WCRU, addr, data)?;
+        Ok(())
     }
 
-    pub fn write_reg_16b(&mut self, lo_addr: u8, data: u16) -> Result<(), Error> {
-        // Unless the register can be written with specific opcode,
-        // use WCRU instruction to write using unbanked (full) address
-        let mut buf: [u8; 4] = [0; 4];
-        let mut data_offset = 0; // number of bytes separating
-                                 // actual data from opcode
-        match lo_addr {
-            addrs::ERXRDPT | addrs::EGPWRPT => {}
-            _ => {
-                buf[1] = lo_addr;
-                data_offset = 1;
-            }
-        }
-        buf[1 + data_offset] = data as u8;
-        buf[2 + data_offset] = (data >> 8) as u8;
-        self.rw_n(
-            &mut buf,
-            match lo_addr {
-                addrs::ERXRDPT => opcodes::WRXRDPT,
-                addrs::EGPWRPT => opcodes::WGPWRPT,
-                _ => opcodes::WCRU,
-            },
-            2 + data_offset, // extra 8-bit lo_addr before data
-        )
+    pub fn write_reg_16b(&mut self, lo_addr: u8, data: u16) -> Result<(), SpiPortError> {
+        self.write_reg_8b(lo_addr, (data & 0xff) as u8)?;
+        self.write_reg_8b(lo_addr + 1, ((data & 0xff00) >> 8) as u8)?;
+        Ok(())
     }
 
-    pub fn send_opcode(&mut self, opcode: u8) -> Result<(), Error> {
-        match opcode {
-            opcodes::SETETHRST | opcodes::SETPKTDEC | opcodes::SETTXRTS | opcodes::ENABLERX => {
-                let mut buf: [u8; 1] = [0];
-                self.rw_n(&mut buf, opcode, 0)
-            }
-            _ => Err(Error::OpcodeError),
-        }
+    pub fn delay_us(&mut self, duration: u16) {
+        self.delay.delay_us(duration)
     }
 
-    // TODO: Actual data should start from buf[0], not buf[1]
-    // Completes an SPI transfer for reading data to the given buffer,
-    // or writing data from the buffer.
-    // It sends an 8-bit instruction, followed by either
-    // receiving or sending n*8-bit data.
-    // The slice of buffer provided must begin with the 8-bit instruction.
-    // If n = 0, the transfer will only involve sending the instruction.
-    fn rw_n<'a>(&mut self, buf: &'a mut [u8], opcode: u8, data_length: usize) -> Result<(), Error> {
-        assert!(buf.len() > data_length);
+    // TODO: Generalise transfer functions
+    // TODO: (Make data read/write as reference to array)
+    // Currently requires 1-byte addr, read/write data is only 1-byte
+    fn rw_addr_u8(&mut self, opcode: u8, addr: u8, data: u8)
+                 -> Result<u8, SpiPortError> {
+        // Enable chip select
+        self.nss.set_low();
+        // Start writing to SLAVE
+        // TODO: don't just use 3 bytes
+        let mut buf: [u8; 3] = [0; 3];
+        buf[0] = opcode;
+        buf[1] = addr;
+        buf[2] = data;
+        match self.spi.transfer(&mut buf) {
+            Ok(_) => {
+                // Disable chip select
+                self.delay_us(1);
+                self.nss.set_high();
+                self.delay_us(1);
+                Ok(buf[2])
+            },
+            // TODO: Maybe too naive?
+            Err(_) => {
+                // Disable chip select
+                self.delay_us(1);
+                self.nss.set_high();
+                self.delay_us(1);
+                Err(SpiPortError::TransferError)
+            }
+        }
+    }
+
+    // TODO: Generalise transfer functions
+    // Currently does NOT accept addr, read data is N-byte long
+    // Returns a reference to the data returned
+    // Note: buf must be at least (data_length + 1)-byte long
+    // TODO: Check and raise error for array size < (data_length + 1)
+    fn r_n<'a>(&mut self, buf: &'a mut [u8], opcode: u8, data_length: usize)
+              -> Result<(), SpiPortError> {
         // Enable chip select
         self.nss.set_low();
-        // >=50ns min. CS_n setup time
-        #[cfg(feature = "cortex-m-cpu")]
-        cortex_m::asm::delay((0.05 * (self.cpu_freq_mhz + 1.)) as u32);
         // Start writing to SLAVE
         buf[0] = opcode;
-        let result = self.spi.transfer(&mut buf[..data_length + 1]);
-        match opcode {
-            opcodes::RCRU | opcodes::WCRU | opcodes::RRXDATA | opcodes::WGPDATA => {
+        match self.spi.transfer(&mut buf[..data_length+1]) {
+            Ok(_) => {
                 // Disable chip select
-                // >=50ns min. CS_n hold time
-                #[cfg(feature = "cortex-m-cpu")]
-                cortex_m::asm::delay((0.05 * (self.cpu_freq_mhz + 1.)) as u32);
                 self.nss.set_high();
-                // >=20ns min. CS_n disable time
-                #[cfg(feature = "cortex-m-cpu")]
-                cortex_m::asm::delay((0.02 * (self.cpu_freq_mhz + 1.)) as u32);
-            }
-            _ => {}
-        }
-        match result {
-            Ok(_) => Ok(()),
+                Ok(())
+            },
             // TODO: Maybe too naive?
-            Err(_) => Err(Error::TransferError),
+            Err(_) => {
+                // Disable chip select
+                self.nss.set_high();
+                Err(SpiPortError::TransferError)
+            }
+        }
+    }
+
+    // Note: buf[0] is currently reserved for opcode to overwrite
+    // TODO: Actual data should start from buf[0], not buf[1]
+    fn w_n<'a>(&mut self, buf: &'a mut [u8], opcode: u8, data_length: usize)
+              -> Result<(), SpiPortError> {
+        // Enable chip select
+        self.nss.set_low();
+        // Start writing to SLAVE
+        buf[0] = opcode;
+        // TODO: Maybe need to copy data to buf later on
+        match self.spi.transfer(&mut buf[..data_length+1]) {
+            Ok(_) => {
+                // Disable chip select
+                self.nss.set_high();
+                Ok(())
+            },
+            // TODO: Maybe too naive?
+            Err(_) => {
+                // Disable chip select
+                self.nss.set_high();
+                Err(SpiPortError::TransferError)
+            }
         }
     }
 }

src/tx.rs

@@ -1,28 +1,32 @@
 use crate::RAW_FRAME_LENGTH_MAX;
 
+/// SRAM Addresses
+pub const GPBUFST_DEFAULT: u16 = 0x0000;    // Start of General-Purpose SRAM Buffer
+pub const GPBUFEN_DEFAULT: u16 = 0x5340;    // End of General-Purpose SRAM Buffer == ERXST default
+
 /// Struct for TX Buffer on the hardware
 /// TODO: Should be a singleton
 pub struct TxBuffer {
-    start_addr: u16,
+    wrap_addr: u16,
     // The following two fields are controlled by firmware
     next_addr: u16,
-    tail_addr: u16,
+    tail_addr: u16
 }
 
 impl TxBuffer {
     pub fn new() -> Self {
         TxBuffer {
-            start_addr: 0x0000,
-            next_addr: 0x0001,
-            tail_addr: 0x0000,
+            wrap_addr: GPBUFST_DEFAULT,
+            next_addr: GPBUFST_DEFAULT + 1,
+            tail_addr: GPBUFST_DEFAULT
         }
     }
 
-    pub fn set_start_addr(&mut self, addr: u16) {
-        self.start_addr = addr;
+    pub fn set_wrap_addr(&mut self, addr: u16) {
+        self.wrap_addr = addr;
     }
-    pub fn get_start_addr(&self) -> u16 {
-        self.start_addr
+    pub fn get_wrap_addr(& self) -> u16{
+        self.wrap_addr
     }
 
     pub fn set_next_addr(&mut self, addr: u16) {
@@ -44,14 +48,14 @@ impl TxBuffer {
 /// TODO: Generalise MAC addresses
 pub struct TxPacket {
     frame: [u8; RAW_FRAME_LENGTH_MAX],
-    frame_length: usize,
+    frame_length: usize
 }
 
 impl TxPacket {
     pub fn new() -> Self {
         TxPacket {
             frame: [0; RAW_FRAME_LENGTH_MAX],
-            frame_length: 0,
+            frame_length: 0
         }
     }