pounder_test/src/adc.rs

222 lines
11 KiB
Rust

///! 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, sampling_timer, DMAReq, DmaConfig, MemoryToPeripheral,
PeripheralToMemory, Priority, TargetAddress, Transfer, SAMPLE_BUFFER_SIZE,
};
// 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. The dimensions are `ADC_BUF[adc_index][ping_pong_index][sample_index]`.
#[link_section = ".axisram.buffers"]
static mut ADC_BUF: [[[u16; SAMPLE_BUFFER_SIZE]; 2]; 2] =
[[[0; SAMPLE_BUFFER_SIZE]; 2]; 2];
macro_rules! adc_input {
($name:ident, $index:literal, $trigger_stream:ident, $data_stream:ident,
$spi:ident, $trigger_channel:ident, $dma_req:ident) => {
/// $spi is used as a type for indicating a DMA transfer into the SPI TX FIFO
/// whenever the tim2 update dma request occurs.
struct $spi {
_channel: sampling_timer::tim2::$trigger_channel,
}
impl $spi {
pub fn new(
_channel: sampling_timer::tim2::$trigger_channel,
) -> Self {
Self { _channel }
}
}
// Note(unsafe): This structure is only safe to instantiate once. The DMA request is hard-coded and
// may only be used if ownership of the timer2 $trigger_channel compare channel is assured, which is
// ensured by maintaining ownership of the channel.
unsafe impl TargetAddress<MemoryToPeripheral> for $spi {
/// SPI is configured to operate using 16-bit transfer words.
type MemSize = u16;
/// SPI DMA requests are generated whenever TIM2 CHx ($dma_req) comparison occurs.
const REQUEST_LINE: Option<u8> = Some(DMAReq::$dma_req as u8);
/// Whenever the DMA request occurs, it should write into SPI's TX FIFO to start a DMA
/// transfer.
fn address(&self) -> u32 {
// Note(unsafe): It is assumed that SPI is owned by another DMA transfer and this DMA is
// only used for the transmit-half of DMA.
let regs = unsafe { &*hal::stm32::$spi::ptr() };
&regs.txdr as *const _ as u32
}
}
/// Represents data associated with ADC.
pub struct $name {
next_buffer: Option<&'static mut [u16; SAMPLE_BUFFER_SIZE]>,
transfer: Transfer<
hal::dma::dma::$data_stream<hal::stm32::DMA1>,
hal::spi::Spi<hal::stm32::$spi, hal::spi::Disabled, u16>,
PeripheralToMemory,
&'static mut [u16; SAMPLE_BUFFER_SIZE],
>,
_trigger_transfer: Transfer<
hal::dma::dma::$trigger_stream<hal::stm32::DMA1>,
$spi,
MemoryToPeripheral,
&'static mut [u16; 1],
>,
}
impl $name {
/// Construct the ADC input channel.
///
/// # Args
/// * `spi` - The SPI interface used to communicate with the ADC.
/// * `trigger_stream` - The DMA stream used to trigger each ADC transfer by writing a word into
/// the SPI TX FIFO.
/// * `data_stream` - The DMA stream used to read samples received over SPI into a data buffer.
/// * `_trigger_channel` - The ADC sampling timer output compare channel for read triggers.
pub fn new(
spi: hal::spi::Spi<hal::stm32::$spi, hal::spi::Enabled, u16>,
trigger_stream: hal::dma::dma::$trigger_stream<
hal::stm32::DMA1,
>,
data_stream: hal::dma::dma::$data_stream<hal::stm32::DMA1>,
trigger_channel: sampling_timer::tim2::$trigger_channel,
) -> Self {
// Generate DMA events when an output compare of the timer hitting zero (timer roll over)
// occurs.
trigger_channel.listen_dma();
trigger_channel.to_output_compare(0);
// 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()
.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,
$spi::new(trigger_channel),
// Note(unsafe): Because this is a Memory->Peripheral transfer, this data is never
// actually modified. It technically only needs to be immutably borrowed, but the
// current HAL API only supports mutable borrows.
unsafe { &mut SPI_START },
None,
trigger_config,
);
// The data stream constantly reads from the SPI RX FIFO into a RAM buffer. The peripheral
// stalls reads of the SPI RX FIFO until data is available, so the DMA transfer completes
// after the requested number of samples have been collected. Note that only ADC1's (sic!)
// data stream is used to trigger a transfer completion interrupt.
let data_config = DmaConfig::default()
.memory_increment(true)
.transfer_complete_interrupt($index == 1)
.priority(Priority::VeryHigh);
// 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,
// Note(unsafe): The ADC_BUF[$index][0] is "owned" by this peripheral.
// It shall not be used anywhere else in the module.
unsafe { &mut ADC_BUF[$index][0] },
None,
data_config,
);
data_transfer.start(|spi| {
// Allow the SPI FIFOs to operate using only DMA data channels.
spi.enable_dma_rx();
spi.enable_dma_tx();
// Enable SPI and start it in infinite transaction mode.
spi.inner().cr1.modify(|_, w| w.spe().set_bit());
spi.inner().cr1.modify(|_, w| w.cstart().started());
});
trigger_transfer.start(|_| {});
Self {
// Note(unsafe): The ADC_BUF[$index][1] is "owned" by this peripheral. It shall not be used
// anywhere else in the module.
next_buffer: unsafe { Some(&mut ADC_BUF[$index][1]) },
transfer: data_transfer,
_trigger_transfer: trigger_transfer,
}
}
/// Obtain a buffer filled with ADC samples.
///
/// # Returns
/// A reference to the underlying buffer that has been filled with ADC samples.
pub fn acquire_buffer(
&mut self,
) -> &'static mut [u16; SAMPLE_BUFFER_SIZE] {
// Wait for the transfer to fully complete before continuing.
// Note: If a device hangs up, check that this conditional is passing correctly, as there is
// no time-out checks here in the interest of execution speed.
while !self.transfer.get_transfer_complete_flag() {}
let next_buffer = self.next_buffer.take().unwrap();
// Start the next transfer.
self.transfer.clear_interrupts();
let (prev_buffer, _) =
self.transfer.next_transfer(next_buffer).unwrap();
prev_buffer
}
/// Release a buffer of ADC samples to the pool.
///
/// # Args
/// * `next_buffer` - Buffer of ADC samples to be re-used.
pub fn release_buffer(
&mut self,
next_buffer: &'static mut [u16; SAMPLE_BUFFER_SIZE],
) {
self.next_buffer.replace(next_buffer); // .unwrap_none() https://github.com/rust-lang/rust/issues/62633
}
}
};
}
adc_input!(Adc0Input, 0, Stream0, Stream1, SPI2, Channel1, TIM2_CH1);
adc_input!(Adc1Input, 1, Stream2, Stream3, SPI3, Channel2, TIM2_CH2);