pounder_test/src/hardware/pounder/timestamp.rs

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///! ADC sample timestamper using external Pounder reference clock.
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///!
///! # Design
///!
///! The pounder timestamper utilizes the pounder SYNC_CLK output as a fast external reference clock
///! for recording a timestamp for each of the ADC samples.
///!
///! To accomplish this, a timer peripheral is configured to be driven by an external clock input.
///! Due to the limitations of clock frequencies allowed by the timer peripheral, the SYNC_CLK input
///! is divided by 4. This clock then clocks the timer peripheral in a free-running mode with an ARR
///! (max count register value) configured to overflow once per ADC sample batch.
///!
///! Once the timer is configured, an input capture is configured to record the timer count
///! register. The input capture is configured to utilize an internal trigger for the input capture.
///! The internal trigger is selected such that when a sample is generated on ADC0, the input
///! capture is simultaneously triggered. This results in the input capture triggering identically
///! to when the ADC samples the input.
///!
///! Once the input capture is properly configured, a DMA transfer is configured to collect all of
///! timestamps. The DMA transfer collects 1 timestamp for each ADC sample collected. In order to
///! avoid potentially losing a timestamp for a sample, the DMA transfer operates in double-buffer
///! mode. As soon as the DMA transfer completes, the hardware automatically swaps over to a second
///! buffer to continue capturing. This alleviates timing sensitivities of the DMA transfer
///! schedule.
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use stm32h7xx_hal as hal;
use hal::dma::{dma::DmaConfig, PeripheralToMemory, Transfer};
use crate::hardware::{design_parameters::SAMPLE_BUFFER_SIZE, timers};
// Three buffers are required for double buffered mode - 2 are owned by the DMA stream and 1 is the
// working data provided to the application. These buffers must exist in a DMA-accessible memory
// region. Note that AXISRAM is not initialized on boot, so their initial contents are undefined.
#[link_section = ".axisram.buffers"]
static mut BUF: [[u16; SAMPLE_BUFFER_SIZE]; 3] = [[0; SAMPLE_BUFFER_SIZE]; 3];
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/// Software unit to timestamp stabilizer ADC samples using an external pounder reference clock.
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pub struct Timestamper {
next_buffer: Option<&'static mut [u16; SAMPLE_BUFFER_SIZE]>,
timer: timers::PounderTimestampTimer,
transfer: Transfer<
hal::dma::dma::Stream0<hal::stm32::DMA2>,
timers::tim8::Channel1InputCapture,
PeripheralToMemory,
&'static mut [u16; SAMPLE_BUFFER_SIZE],
hal::dma::DBTransfer,
>,
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}
impl Timestamper {
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/// Construct the pounder sample timestamper.
///
/// # Note
/// The DMA is immediately configured after instantiation. It will not collect any samples
/// until the sample timer begins to cause input capture triggers.
///
/// # Args
/// * `timestamp_timer` - The timer peripheral used for capturing timestamps from.
/// * `stream` - The DMA stream to use for collecting timestamps.
/// * `capture_channel` - The input capture channel for collecting timestamps.
/// * `sampling_timer` - The stabilizer ADC sampling timer.
/// * `_clock_input` - The input pin for the external clock from Pounder.
///
/// # Returns
/// The new pounder timestamper in an operational state.
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pub fn new(
mut timestamp_timer: timers::PounderTimestampTimer,
stream: hal::dma::dma::Stream0<hal::stm32::DMA2>,
capture_channel: timers::tim8::Channel1,
sampling_timer: &mut timers::SamplingTimer,
_clock_input: hal::gpio::gpioa::PA0<
hal::gpio::Alternate<hal::gpio::AF3>,
>,
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) -> Self {
let config = DmaConfig::default()
.memory_increment(true)
.circular_buffer(true)
.double_buffer(true);
// The sampling timer should generate a trigger output when CH1 comparison occurs.
sampling_timer.generate_trigger(timers::TriggerGenerator::ComparePulse);
// The timestamp timer trigger input should use TIM2 (SamplingTimer)'s trigger, which is
// mapped to ITR1.
timestamp_timer.set_trigger_source(timers::TriggerSource::Trigger1);
// The capture channel should capture whenever the trigger input occurs.
let input_capture = capture_channel
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.into_input_capture(timers::tim8::CaptureSource1::TRC);
input_capture.listen_dma();
// The data transfer is always a transfer of data from the peripheral to a RAM buffer.
let data_transfer: Transfer<_, _, PeripheralToMemory, _, _> =
Transfer::init(
stream,
input_capture,
// Note(unsafe): BUF[0] and BUF[1] are "owned" by this peripheral.
// They shall not be used anywhere else in the module.
unsafe { &mut BUF[0] },
unsafe { Some(&mut BUF[1]) },
config,
);
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Self {
timer: timestamp_timer,
transfer: data_transfer,
// Note(unsafe): BUF[2] is "owned" by this peripheral. It shall not be used anywhere
// else in the module.
next_buffer: unsafe { Some(&mut BUF[2]) },
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}
}
/// Start the DMA transfer for collecting timestamps.
#[allow(dead_code)]
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pub fn start(&mut self) {
self.transfer
.start(|capture_channel| capture_channel.enable());
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}
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/// Update the period of the underlying timestamp timer.
#[allow(dead_code)]
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pub fn update_period(&mut self, period: u16) {
self.timer.set_period_ticks(period);
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}
/// Obtain a buffer filled with timestamps.
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///
/// # Returns
/// A reference to the underlying buffer that has been filled with timestamps.
#[allow(dead_code)]
pub fn acquire_buffer(&mut self) -> &[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.
let (prev_buffer, _, _) =
self.transfer.next_transfer(next_buffer).unwrap();
self.next_buffer.replace(prev_buffer); // .unwrap_none() https://github.com/rust-lang/rust/issues/62633
self.next_buffer.as_ref().unwrap()
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}
}