use semihosting with a feature-flag

Cargo.toml

@@ -19,11 +19,12 @@ features = []
 default-target = "thumbv7em-none-eabihf"
 
 [dependencies]
-panic-abort = "0.3.1"
-
+panic-abort = { version = "0.3.1" }
+panic-semihosting = { version = "0.5.1", optional = true }
+log = "0.4"
 cortex-m = "0.5"
 cortex-m-rt = { version = "0.6", features = ["device"] }
-cortex-m-semihosting = "0.3"
+cortex-m-log = { version = "0.4", features = ["log-integration"] }
 stm32f4 = { version = "0.6", features = ["rt", "stm32f429"] }
 embedded-hal = "0.2"
 stm32f4xx-hal = { git = "https://github.com/stm32-rs/stm32f4xx-hal.git", features = ["rt", "stm32f429"] }
@@ -31,6 +32,8 @@ stm32f4xx-hal = { git = "https://github.com/stm32-rs/stm32f4xx-hal.git", feature
 stm32-eth = { version = "0.1.0", features = ["smoltcp-phy", "nucleo-f429zi"] }
 smoltcp = { version = "0.5.0", default-features = false, features = ["proto-ipv4", "proto-ipv6", "socket-icmp", "socket-udp", "socket-tcp", "log", "verbose"] }
 
+[features]
+semihosting = ["panic-semihosting", "cortex-m-log/semihosting"]
 
 [profile.release]
 codegen-units = 1

shell.nix

@@ -24,7 +24,7 @@ stdenv.mkDerivation {
     # Let openocd output scroll by
     sleep 1
 
-    echo "Run 'cargo build --release'"
+    echo "Run 'cargo build --release --features=semihosting'"
     echo "Then 'gdb target/thumbv7em-none-eabihf/release/adc2tcp'"
   '';
 }

src/main.rs

@@ -4,8 +4,15 @@
 #![feature(never_type)]
 
 #[allow(unused_extern_crates)]
+#[cfg(not(feature = "semihosting"))]
 extern crate panic_abort;
+#[cfg(feature = "semihosting")]
+extern crate panic_semihosting;
 
+#[macro_use]
+extern crate log;
+
+use core::fmt::Write;
 use cortex_m::asm::wfi;
 use cortex_m_rt::entry;
 use embedded_hal::watchdog::{WatchdogEnable, Watchdog};
@@ -18,9 +25,6 @@ use stm32f4xx_hal::{
 };
 use smoltcp::time::Instant;
 
-use core::fmt::Write;
-use cortex_m_semihosting::hio;
-
 mod adc_input;
 mod net;
 mod server;
@@ -29,10 +33,30 @@ mod timer;
 
 const OUTPUT_INTERVAL: u32 = 1000;
 
+#[cfg(not(feature = "semihosting"))]
+fn init_log() {}
+
+#[cfg(feature = "semihosting")]
+fn init_log() {
+    use log::LevelFilter;
+    use cortex_m_log::log::{Logger, init};
+    use cortex_m_log::printer::semihosting::{InterruptOk, hio::HStdout};
+    static mut LOGGER: Option<Logger<InterruptOk<HStdout>>> = None;
+    let logger = Logger {
+        inner: InterruptOk::<_>::stdout().expect("semihosting stdout"),
+        level: LevelFilter::Info,
+    };
+    let logger = unsafe {
+        LOGGER.get_or_insert(logger)
+    };
+
+    init(logger).expect("set logger");
+}
+
 #[entry]
 fn main() -> ! {
-    let mut stdout = hio::hstdout().unwrap();
-    writeln!(stdout, "adc2tcp").unwrap();
+    init_log();
+    info!("adc2tcp");
 
     let mut cp = CorePeripherals::take().unwrap();
     cp.SCB.enable_icache();
@@ -57,19 +81,19 @@ fn main() -> ! {
     let gpioc = dp.GPIOC.split();
     let gpiog = dp.GPIOG.split();
 
-    writeln!(stdout, "ADC init").unwrap();
+    info!("ADC init");
     adc_input::setup(&mut cp.NVIC, dp.ADC1, gpioa.pa3);
 
-    writeln!(stdout, "Eth setup").unwrap();
+    info!("Eth setup");
     stm32_eth::setup_pins(
         gpioa.pa1, gpioa.pa2, gpioa.pa7, gpiob.pb13, gpioc.pc1,
         gpioc.pc4, gpioc.pc5, gpiog.pg11, gpiog.pg13
     );
 
-    writeln!(stdout, "Timer setup").unwrap();
+    info!("Timer setup");
     timer::setup(cp.SYST, clocks);
 
-    writeln!(stdout, "Net startup").unwrap();
+    info!("Net startup");
     net::run(&mut cp.NVIC, dp.ETHERNET_MAC, dp.ETHERNET_DMA, |net| {
         let mut server = Server::new(net);