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stm32 ringbuffered adc docs improvements

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This commit is contained in:
Andres Vahter 2024-07-02 17:35:15 +03:00
parent dd69efe708
commit d4ff7616f9
1 changed files with 7 additions and 10 deletions
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17
embassy-stm32/src/adc/ringbuffered_v2.rs
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@ -93,11 +93,12 @@ pub struct RingBufferedAdc<'d, T: Instance> {
impl<'d, T: Instance> Adc<'d, T> {
/// Configures the ADC to use a DMA ring buffer for continuous data acquisition.
///
/// The `dma_buf` should be large enough to prevent buffer overflow, allowing sufficient time to read out measurements.
/// The `dma_buf` should be large enough to prevent DMA buffer overrun.
/// The length of the `dma_buf` should be a multiple of the ADC channel count.
/// For example, if 3 channels are measured, its length can be 3 * 40 = 120 measurements.
///
/// `read_exact` method is used to read out measurements from the DMA ring buffer, and its buffer should be exactly half of the `dma_buf` length.
/// It is critical to call `read_exact` frequently to prevent DMA buffer overrun.
///
/// [`read_exact`]: #method.read_exact
pub fn into_ring_buffered(
@ -358,18 +359,17 @@ impl<'d, T: Instance> RingBufferedAdc<'d, T> {
/// Reads measurements from the DMA ring buffer.
///
/// This method fills the provided `measurements` array with ADC readings.
/// The length of the `measurements` array should be exactly half of the DMA buffer length.
/// Because interrupts are only generated if half or full DMA transfer completes.
/// This method fills the provided `measurements` array with ADC readings from the DMA buffer.
/// The length of the `measurements` array should be exactly half of the DMA buffer length. Because interrupts are only generated if half or full DMA transfer completes.
///
/// Each call to `read_exact` will populate the `measurements` array in the same order as the channels defined with `set_sample_sequence`.
/// There will be many sequences worth of measurements in this array because it only returns if at least half of the DMA buffer is filled.
/// For example if 3 channels are sampled `measurements` contain: `[sq0 sq1 sq3 sq0 sq1 sq3 sq0 sq1 sq3 sq0 sq1 sq3..]`.
///
/// If an error is returned, it indicates a DMA overrun, and the process must be restarted by calling `start` again.
/// If an error is returned, it indicates a DMA overrun, and the process must be restarted by calling `start` or `read_exact` again.
///
/// By default, the ADC fills the DMA buffer as quickly as possible. To control the sample rate, call `teardown_adc` after each readout, and then start the DMA again at the desired interval.
/// Note that even if using `teardown_adc` to control sample rate, with each call to `read_exact`, measurements equivalent to half the size of the DMA buffer are still collected.
/// Note that even if using `teardown_adc` to control the sample rate, with each call to `read_exact`, measurements equivalent to half the size of the DMA buffer are still collected.
///
/// Example:
/// ```rust,ignore
@ -381,7 +381,6 @@ impl<'d, T: Instance> RingBufferedAdc<'d, T> {
/// adc.set_sample_sequence(Sequence::Two, &mut p.PA1, SampleTime::CYCLES112);
/// adc.set_sample_sequence(Sequence::Three, &mut p.PA2, SampleTime::CYCLES112);
///
/// adc.start.unwrap();
/// let mut measurements = [0u16; DMA_BUF_LEN / 2];
/// loop {
/// match adc.read_exact(&mut measurements).await {
@ -392,14 +391,12 @@ impl<'d, T: Instance> RingBufferedAdc<'d, T> {
/// }
/// Err(e) => {
/// defmt::warn!("Error: {:?}", e);
/// // DMA overflow, restart ADC.
/// let _ = adc.start();
/// // DMA overrun, next call to `read_exact` restart ADC.
/// }
/// }
///
/// // Manually control sample rate.
/// Timer::after_millis(100).await;
/// let _ = adc.start();
/// }
/// ```
///