Adding updated docs for adc file

Cargo.lock

@@ -501,7 +501,7 @@ dependencies = [
 [[package]]
 name = "stm32h7xx-hal"
 version = "0.8.0"
-source = "git+https://github.com/quartiq/stm32h7xx-hal?branch=feature/stabilizer-dma#5fbbfa9352f720994c210e5c21601f3acf9dc40c"
+source = "git+https://github.com/quartiq/stm32h7xx-hal?branch=feature/dma-rtic-example#d8cb6fa5099282665f5e5068a9dcdc9ebaa63240"
 dependencies = [
  "bare-metal 1.0.0",
  "cast",

Cargo.toml

@@ -55,7 +55,7 @@ path = "ad9959"
 [dependencies.stm32h7xx-hal]
 features = ["stm32h743v", "rt", "unproven", "ethernet", "quadspi"]
 git = "https://github.com/quartiq/stm32h7xx-hal"
-branch = "feature/stabilizer-dma"
+branch = "feature/dma-rtic-example"
 
 [features]
 semihosting = ["panic-semihosting", "cortex-m-log/semihosting"]
@@ -65,7 +65,7 @@ nightly = ["cortex-m/inline-asm"]
 [profile.dev]
 codegen-units = 1
 incremental = false
-opt-level = 1
+opt-level = 3
 
 [profile.release]
 opt-level = 3

src/adc.rs

@@ -1,13 +1,36 @@
+///! Stabilizer ADC management interface
+///!
+///! The Stabilizer ADCs utilize a DMA channel to trigger sampling. The SPI streams are configured
+///! for full-duplex operation, but only RX is connected to physical pins. A timer channel is
+///! configured to generate a DMA write into the SPI TXFIFO, which initiates a SPI transfer and
+///! results in an ADC sample read for both channels.
+///!
+///! In order to read multiple samples without interrupting the CPU, a separate DMA transfer is
+///! configured to read from each of the ADC SPI RX FIFOs. Due to the design of the SPI peripheral,
+///! these DMA transfers stall when no data is available in the FIFO. Thus, the DMA transfer only
+///! completes after all samples have been read. When this occurs, a CPU interrupt is generated so
+///! that software can process the acquired samples from both ADCs. Only one of the ADC DMA streams
+///! is configured to generate an interrupt to handle both transfers, so it is necessary to ensure
+///! both transfers are completed before reading the data. This is usually not significant for
+///! busy-waiting because the transfers should complete at approximately the same time.
 use super::{
-    hal, DMAReq, DmaConfig, MemoryToPeripheral, PeripheralToMemory, Priority,
+    hal, DMAReq, DmaConfig, MemoryToPeripheral, PeripheralToMemory, Priority, TargetAddress,
-    Stream, TargetAddress, Transfer,
+        Transfer,
 };
 
+// The desired ADC input buffer size. This is use configurable.
 const INPUT_BUFFER_SIZE: usize = 1;
 
+// The following data is written by the timer ADC sample trigger into each of the SPI TXFIFOs. Note
+// that because the SPI MOSI line is not connected, this data is dont-care. Data in AXI SRAM is not
+// initialized on boot, so the contents are random.
 #[link_section = ".axisram.buffers"]
 static mut SPI_START: [u16; 1] = [0x00];
 
+// The following global buffers are used for the ADC sample DMA transfers. Two buffers are used for
+// each transfer in a ping-pong buffer configuration (one is being acquired while the other is being
+// processed). Note that the contents of AXI SRAM is uninitialized, so the buffer contents on
+// startup are undefined.
 #[link_section = ".axisram.buffers"]
 static mut ADC0_BUF0: [u16; INPUT_BUFFER_SIZE] = [0; INPUT_BUFFER_SIZE];
 
@@ -20,8 +43,9 @@ static mut ADC1_BUF0: [u16; INPUT_BUFFER_SIZE] = [0; INPUT_BUFFER_SIZE];
 #[link_section = ".axisram.buffers"]
 static mut ADC1_BUF1: [u16; INPUT_BUFFER_SIZE] = [0; INPUT_BUFFER_SIZE];
 
+/// SPI2 is used as a ZST (zero-sized type) for indicating a DMA transfer into the SPI2 TX FIFO
+/// whenever the tim2 update dma request occurs.
 struct SPI2 {}
-
 impl SPI2 {
     pub fn new() -> Self {
         Self {}
@@ -29,18 +53,23 @@ impl SPI2 {
 }
 
 unsafe impl TargetAddress<MemoryToPeripheral> for SPI2 {
+    /// SPI2 is configured to operate using 16-bit transfer words.
     type MemSize = u16;
 
-    const REQUEST_LINE: Option<u8> = Some(DMAReq::TIM2_UP as u8);
+    /// SPI2 DMA requests are generated whenever TIM2 CH1 comparison occurs.
+    const REQUEST_LINE: Option<u8> = Some(DMAReq::TIM2_CH1 as u8);
 
+    /// Whenever the DMA request occurs, it should write into SPI2's TX FIFO to start a DMA
+    /// transfer.
     fn address(&self) -> u32 {
         let regs = unsafe { &*hal::stm32::SPI2::ptr() };
         &regs.txdr as *const _ as u32
     }
 }
 
+/// SPI3 is used as a ZST (zero-sized type) for indicating a DMA transfer into the SPI3 TX FIFO
+/// whenever the tim2 update dma request occurs.
 struct SPI3 {}
-
 impl SPI3 {
     pub fn new() -> Self {
         Self {}
@@ -48,26 +77,37 @@ impl SPI3 {
 }
 
 unsafe impl TargetAddress<MemoryToPeripheral> for SPI3 {
+    /// SPI3 is configured to operate using 16-bit transfer words.
     type MemSize = u16;
 
-    const REQUEST_LINE: Option<u8> = Some(DMAReq::TIM2_UP as u8);
+    /// SPI3 DMA requests are generated whenever TIM2 CH2 comparison occurs.
+    const REQUEST_LINE: Option<u8> = Some(DMAReq::TIM2_CH2 as u8);
 
+    /// Whenever the DMA request occurs, it should write into SPI3's TX FIFO to start a DMA
+    /// transfer.
     fn address(&self) -> u32 {
         let regs = unsafe { &*hal::stm32::SPI3::ptr() };
         &regs.txdr as *const _ as u32
     }
 }
 
+/// Represents both ADC input channels.
 pub struct AdcInputs {
     adc0: Adc0Input,
     adc1: Adc1Input,
 }
 
 impl AdcInputs {
+    /// Construct the ADC inputs.
     pub fn new(adc0: Adc0Input, adc1: Adc1Input) -> Self {
         Self { adc0, adc1 }
     }
 
+    /// Interrupt handler to handle when the sample collection DMA transfer completes.
+    ///
+    /// # Returns
+    /// (adc0, adc1) where adcN is a reference to the collected ADC samples. Two array references
+    /// are returned - one for each ADC sample stream.
     pub fn transfer_complete_handler(
         &mut self,
     ) -> (&[u16; INPUT_BUFFER_SIZE], &[u16; INPUT_BUFFER_SIZE]) {
@@ -77,6 +117,7 @@ impl AdcInputs {
     }
 }
 
+/// Represents data associated with ADC0.
 pub struct Adc0Input {
     next_buffer: Option<&'static mut [u16; INPUT_BUFFER_SIZE]>,
     transfer: Transfer<
@@ -85,72 +126,113 @@ pub struct Adc0Input {
         PeripheralToMemory,
         &'static mut [u16; INPUT_BUFFER_SIZE],
     >,
+    _trigger_transfer: Transfer<
+        hal::dma::dma::Stream0<hal::stm32::DMA1>,
+        SPI2,
+        MemoryToPeripheral,
+        &'static mut [u16; 1],
+    >,
 }
 
 impl Adc0Input {
+    /// Construct the ADC0 input channel.
+    ///
+    /// # Args
+    /// * `spi` - The SPI interface used to communicate with the ADC.
+    /// * `trigger_stream` - The DMA stream used to trigger each ADC transfer by writing a word into
+    ///   the SPI TX FIFO.
+    /// * `data_stream` - The DMA stream used to read samples received over SPI into a data buffer.
     pub fn new(
         spi: hal::spi::Spi<hal::stm32::SPI2, hal::spi::Enabled, u16>,
         trigger_stream: hal::dma::dma::Stream0<hal::stm32::DMA1>,
         data_stream: hal::dma::dma::Stream1<hal::stm32::DMA1>,
     ) -> Self {
+        // The trigger stream constantly writes to the TX FIFO using a static word (dont-care
+        // contents). Thus, neither the memory or peripheral address ever change. This is run in
+        // circular mode to be completed at every DMA request.
         let trigger_config = DmaConfig::default()
             .memory_increment(false)
             .peripheral_increment(false)
             .priority(Priority::High)
             .circular_buffer(true);
 
+        // Construct the trigger stream to write from memory to the peripheral.
         let mut trigger_transfer: Transfer<_, _, MemoryToPeripheral, _> =
             Transfer::init(
                 trigger_stream,
-                &SPI2::new(),
+                SPI2::new(),
                 unsafe { &mut SPI_START },
                 None,
                 trigger_config,
             );
 
+        // The data stream constantly reads from the SPI RX FIFO into a RAM buffer. The peripheral
+        // stalls reads of the SPI RX FIFO until data is available, so the DMA transfer completes
+        // after the requested number of samples have been collected. Note that only ADC1's data
+        // stream is used to trigger a transfer completion interrupt.
         let data_config = DmaConfig::default()
             .memory_increment(true)
             .priority(Priority::VeryHigh)
             .peripheral_increment(false);
 
+        // A SPI peripheral error interrupt is used to determine if the RX FIFO overflows. This
+        // indicates that samples were dropped due to excessive processing time in the main
+        // application (e.g. a second DMA transfer completes before the first was done with
+        // processing). This is used as a flow control indicator to guarantee that no ADC samples
+        // are lost.
         let mut spi = spi.disable();
         spi.listen(hal::spi::Event::Error);
 
+        // The data transfer is always a transfer of data from the peripheral to a RAM buffer.
         let mut data_transfer: Transfer<_, _, PeripheralToMemory, _> =
             Transfer::init(
                 data_stream,
-                &spi,
+                spi,
                 unsafe { &mut ADC0_BUF0 },
                 None,
                 data_config,
             );
 
-        spi.enable_dma_rx();
+        data_transfer.start(|spi| {
-        spi.enable_dma_tx();
+            // Allow the SPI FIFOs to operate using only DMA data channels.
+            spi.enable_dma_rx();
+            spi.enable_dma_tx();
 
-        let spi = spi.enable();
+            // Enable SPI and start it in infinite transaction mode.
-        spi.inner().cr1.modify(|_, w| w.cstart().started());
+            spi.inner().cr1.modify(|_, w| w.spe().set_bit());
+            spi.inner().cr1.modify(|_, w| w.cstart().started());
+        });
 
-        data_transfer.start();
+        trigger_transfer.start(|_| {});
-        trigger_transfer.start();
 
         Self {
             next_buffer: unsafe { Some(&mut ADC0_BUF1) },
             transfer: data_transfer,
+            _trigger_transfer: trigger_transfer,
         }
     }
 
+    /// Handle a transfer completion.
+    ///
+    /// # Returns
+    /// A reference to the underlying buffer that has been filled with ADC samples.
     pub fn transfer_complete_handler(&mut self) -> &[u16; INPUT_BUFFER_SIZE] {
         let next_buffer = self.next_buffer.take().unwrap();
-        while hal::dma::dma::Stream1::<hal::stm32::DMA1>::is_enabled() {}
+
+        // Wait for the transfer to fully complete before continuing.
+        while self.transfer.get_transfer_complete_flag() == false {}
+
+        // Start the next transfer.
         self.transfer.clear_interrupts();
         let (prev_buffer, _) =
             self.transfer.next_transfer(next_buffer).unwrap();
+
         self.next_buffer.replace(prev_buffer);
         self.next_buffer.as_ref().unwrap()
     }
 }
 
+/// Represents the data input stream from ADC1
 pub struct Adc1Input {
     next_buffer: Option<&'static mut [u16; INPUT_BUFFER_SIZE]>,
     transfer: Transfer<
@@ -159,68 +241,107 @@ pub struct Adc1Input {
         PeripheralToMemory,
         &'static mut [u16; INPUT_BUFFER_SIZE],
     >,
+    _trigger_transfer: Transfer<
+        hal::dma::dma::Stream2<hal::stm32::DMA1>,
+        SPI3,
+        MemoryToPeripheral,
+        &'static mut [u16; 1],
+    >,
 }
 
 impl Adc1Input {
+    /// Construct a new ADC1 input data stream.
+    ///
+    /// # Args
+    /// * `spi` - The SPI interface connected to ADC1.
+    /// * `trigger_stream` - The DMA stream used to trigger ADC conversions on the SPI interface.
+    /// * `data_stream` - The DMA stream used to read ADC samples from the SPI RX FIFO.
     pub fn new(
         spi: hal::spi::Spi<hal::stm32::SPI3, hal::spi::Enabled, u16>,
         trigger_stream: hal::dma::dma::Stream2<hal::stm32::DMA1>,
         data_stream: hal::dma::dma::Stream3<hal::stm32::DMA1>,
     ) -> Self {
+        // The trigger stream constantly writes to the TX FIFO using a static word (dont-care
+        // contents). Thus, neither the memory or peripheral address ever change. This is run in
+        // circular mode to be completed at every DMA request.
         let trigger_config = DmaConfig::default()
             .memory_increment(false)
             .peripheral_increment(false)
             .priority(Priority::High)
             .circular_buffer(true);
 
+        // Construct the trigger stream to write from memory to the peripheral.
         let mut trigger_transfer: Transfer<_, _, MemoryToPeripheral, _> =
             Transfer::init(
                 trigger_stream,
-                &SPI3::new(),
+                SPI3::new(),
                 unsafe { &mut SPI_START },
                 None,
                 trigger_config,
             );
 
+        // The data stream constantly reads from the SPI RX FIFO into a RAM buffer. The peripheral
+        // stalls reads of the SPI RX FIFO until data is available, so the DMA transfer completes
+        // after the requested number of samples have been collected. Note that only ADC1's data
+        // stream is used to trigger a transfer completion interrupt.
         let data_config = DmaConfig::default()
             .memory_increment(true)
             .transfer_complete_interrupt(true)
             .priority(Priority::VeryHigh)
             .peripheral_increment(false);
 
+        // A SPI peripheral error interrupt is used to determine if the RX FIFO overflows. This
+        // indicates that samples were dropped due to excessive processing time in the main
+        // application (e.g. a second DMA transfer completes before the first was done with
+        // processing). This is used as a flow control indicator to guarantee that no ADC samples
+        // are lost.
         let mut spi = spi.disable();
         spi.listen(hal::spi::Event::Error);
 
+        // The data transfer is always a transfer of data from the peripheral to a RAM buffer.
         let mut data_transfer: Transfer<_, _, PeripheralToMemory, _> =
             Transfer::init(
                 data_stream,
-                &spi,
+                spi,
                 unsafe { &mut ADC1_BUF0 },
                 None,
                 data_config,
             );
 
-        spi.enable_dma_rx();
+        data_transfer.start(|spi| {
-        spi.enable_dma_tx();
+            // Allow the SPI FIFOs to operate using only DMA data channels.
+            spi.enable_dma_rx();
+            spi.enable_dma_tx();
 
-        let spi = spi.enable();
+            // Enable SPI and start it in infinite transaction mode.
-        spi.inner().cr1.modify(|_, w| w.cstart().started());
+            spi.inner().cr1.modify(|_, w| w.spe().set_bit());
+            spi.inner().cr1.modify(|_, w| w.cstart().started());
+        });
 
-        data_transfer.start();
+        trigger_transfer.start(|_| {});
-        trigger_transfer.start();
 
         Self {
             next_buffer: unsafe { Some(&mut ADC1_BUF1) },
             transfer: data_transfer,
+            _trigger_transfer: trigger_transfer,
         }
     }
 
+    /// Handle a transfer completion.
+    ///
+    /// # Returns
+    /// A reference to the underlying buffer that has been filled with ADC samples.
     pub fn transfer_complete_handler(&mut self) -> &[u16; INPUT_BUFFER_SIZE] {
         let next_buffer = self.next_buffer.take().unwrap();
-        while hal::dma::dma::Stream3::<hal::stm32::DMA1>::is_enabled() {}
+
+        // Wait for the transfer to fully complete before continuing.
+        while self.transfer.get_transfer_complete_flag() == false {}
+
+        // Start the next transfer.
         self.transfer.clear_interrupts();
         let (prev_buffer, _) =
             self.transfer.next_transfer(next_buffer).unwrap();
+
         self.next_buffer.replace(prev_buffer);
         self.next_buffer.as_ref().unwrap()
     }

src/main.rs

@@ -1,6 +1,4 @@
 #![deny(warnings)]
-// Deprecation warnings are temporarily allowed as the HAL DMA goes through updates.
-#![allow(deprecated)]
 #![allow(clippy::missing_safety_doc)]
 #![no_std]
 #![no_main]
@@ -41,7 +39,7 @@ use hal::{
     dma::{
         config::Priority,
         dma::{DMAReq, DmaConfig},
-        traits::{Stream, TargetAddress},
+        traits::TargetAddress,
         MemoryToPeripheral, PeripheralToMemory, Transfer,
     },
     ethernet::{self, PHY},
@@ -706,8 +704,14 @@ const APP: () = {
             &ccdr.clocks,
         );
         {
+            // Listen to the CH1 and CH2 comparison events. These channels should have a value of
+            // zero loaded into them, so the event should occur whenever the timer overflows. Note
+            // that we use channels instead of timer updates because each SPI DMA transfer needs a
+            // unique request line.
             let t2_regs = unsafe { &*hal::stm32::TIM2::ptr() };
-            t2_regs.dier.modify(|_, w| w.ude().set_bit());
+            t2_regs
+                .dier
+                .modify(|_, w| w.cc1de().set_bit().cc2de().set_bit());
         }
 
         init::LateResources {