pounder_test/src/hardware/adc.rs

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///! Stabilizer ADC management interface
///!
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///! # Design
///!
///! Stabilizer ADCs are connected to the MCU via a simplex, SPI-compatible interface. The ADCs
///! require a setup conversion time after asserting the CSn (convert) signal to generate the ADC
///! code from the sampled level. Once the setup time has elapsed, the ADC data is clocked out of
///! MISO. The internal setup time is managed by the SPI peripheral via a CSn setup time parameter
///! during SPI configuration, which allows offloading the management of the setup time to hardware.
///!
///! Because of the SPI-compatibility of the ADCs, a single SPI peripheral + DMA is used to automate
///! the collection of multiple ADC samples without requiring processing by the CPU, which reduces
///! overhead and provides the CPU with more time for processing-intensive tasks, like DSP.
///!
///! The automation of sample collection utilizes three DMA streams, the SPI peripheral, and two
///! timer compare channel for each ADC. One timer comparison channel is configured to generate a
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///! comparison event every time the timer is equal to a specific value. Each comparison then
///! generates a DMA transfer event to write into the SPI CR1 register to initiate the transfer.
///! This allows the SPI interface to periodically read a single sample. The other timer comparison
///! channel is configured to generate a comparison event slightly before the first (~10 timer
///! cycles). This channel triggers a separate DMA stream to clear the EOT flag within the SPI
///! peripheral. The EOT flag must be cleared after each transfer or the SPI peripheral will not
///! properly complete the single conversion. Thus, by using two DMA streams and timer comparison
///! channels, the SPI can regularly acquire ADC samples.
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///!
///! In order to collect the acquired ADC samples into a RAM buffer, a final DMA transfer is
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///! configured to read from the SPI RX FIFO into RAM. The request for this transfer is connected to
///! the SPI RX data signal, so the SPI peripheral will request to move data into RAM whenever it is
///! available. When enough samples have been collected, a transfer-complete interrupt is generated
///! and the ADC samples are available for processing.
///!
///! The SPI peripheral internally has an 8- or 16-byte TX and RX FIFO, which corresponds to a 4- or
///! 8-sample buffer for incoming ADC samples. During the handling of the DMA transfer completion,
///! there is a small window where buffers are swapped over where it's possible that a sample could
///! be lost. In order to avoid this, the SPI RX FIFO is effectively used as a "sample overflow"
///! region and can buffer a number of samples until the next DMA transfer is configured. If a DMA
///! transfer is still not set in time, the SPI peripheral will generate an input-overrun interrupt.
///! This interrupt then serves as a means of detecting if samples have been lost, which will occur
///! whenever data processing takes longer than the collection period.
///!
///!
///! ## Starting Data Collection
///!
///! Because the DMA data collection is automated via timer count comparisons and DMA transfers, the
///! ADCs can be initialized and configured, but will not begin sampling the external ADCs until the
///! sampling timer is enabled. As such, the sampling timer should be enabled after all
///! initialization has completed and immediately before the embedded processing loop begins.
///!
///!
///! ## Batch Sizing
///!
///! The ADCs collect a group of N samples, which is referred to as a batch. The size of the batch
///! is configured by the user at compile-time to allow for a custom-tailored implementation. Larger
///! batch sizes generally provide for lower overhead and more processing time per sample, but come
///! at the expense of increased input -> output latency.
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///!
///!
///! # Note
///!
///! While there are two ADCs, only a single ADC is configured to generate transfer-complete
///! interrupts. This is done because it is assumed that the ADCs will always be sampled
///! simultaneously. If only a single ADC is used, it must always be ADC0, as ADC1 will not generate
///! transfer-complete interrupts.
///!
///! There is a very small amount of latency between sampling of ADCs due to bus matrix priority. As
///! such, one of the ADCs will be sampled marginally earlier before the other because the DMA
///! requests are generated simultaneously. This can be avoided by providing a known offset to the
///! sample DMA requests, which can be completed by setting e.g. ADC0's comparison to a counter
///! value of 0 and ADC1's comparison to a counter value of 1.
///!
///! In this implementation, single buffer mode DMA transfers are used because the SPI RX FIFO can
///! be used as a means to both detect and buffer ADC samples during the buffer swap-over. Because
///! of this, double-buffered mode does not offer any advantages over single-buffered mode (unless
///! double-buffered mode offers less overhead due to the DMA disable/enable procedure).
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use stm32h7xx_hal as hal;
use super::design_parameters::SAMPLE_BUFFER_SIZE;
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use super::timers;
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use hal::dma::{
config::Priority,
dma::{DMAReq, DmaConfig},
traits::TargetAddress,
MemoryToPeripheral, PeripheralToMemory, Transfer,
};
// The following data is written by the timer ADC sample trigger into the SPI CR1 to start the
// transfer. Data in AXI SRAM is not initialized on boot, so the contents are random. This value is
// initialized during setup.
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#[link_section = ".axisram.buffers"]
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static mut SPI_START: [u32; 1] = [0x00; 1];
// The following data is written by the timer flag clear trigger into the SPI IFCR register to clear
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// the EOT flag. Data in AXI SRAM is not initialized on boot, so the contents are random. This
// value is initialized during setup.
#[link_section = ".axisram.buffers"]
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static mut SPI_EOT_CLEAR: [u32; 1] = [0x00];
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// 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
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// startup are undefined. The dimensions are `ADC_BUF[adc_index][ping_pong_index][sample_index]`.
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#[link_section = ".axisram.buffers"]
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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, $clear_stream:ident,
$spi:ident, $trigger_channel:ident, $dma_req:ident, $clear_channel:ident, $dma_clear_req:ident) => {
paste::paste! {
/// $spi-CR is used as a type for indicating a DMA transfer into the SPI control
/// register whenever the tim2 update dma request occurs.
struct [< $spi CR >] {
_channel: timers::tim2::$trigger_channel,
}
impl [< $spi CR >] {
pub fn new(_channel: timers::tim2::$trigger_channel) -> Self {
Self { _channel }
}
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}
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// 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 [< $spi CR >] {
type MemSize = u32;
/// SPI DMA requests are generated whenever TIM2 CHx ($dma_req) comparison occurs.
const REQUEST_LINE: Option<u8> = Some(DMAReq::$dma_req as u8);
/// Whenever the DMA request occurs, it should write into SPI's CR1 to start the
/// transfer.
fn address(&self) -> usize {
// Note(unsafe): It is assumed that SPI is owned by another DMA transfer. This
// is only safe because we are writing to a configuration register.
let regs = unsafe { &*hal::stm32::$spi::ptr() };
&regs.cr1 as *const _ as usize
}
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}
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/// $spi-IFCR is used as a type for indicating a DMA transfer into the SPI flag clear
/// register whenever the tim3 compare dma request occurs. The flag must be cleared
/// before the transfer starts.
struct [< $spi IFCR >] {
_channel: timers::tim3::$clear_channel,
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}
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impl [< $spi IFCR >] {
pub fn new(_channel: timers::tim3::$clear_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 timer3 $clear_channel compare
// channel is assured, which is ensured by maintaining ownership of the channel.
unsafe impl TargetAddress<MemoryToPeripheral> for [< $spi IFCR >] {
type MemSize = u32;
/// SPI DMA requests are generated whenever TIM3 CHx ($dma_clear_req) comparison
/// occurs.
const REQUEST_LINE: Option<u8> = Some(DMAReq::$dma_clear_req as u8);
/// Whenever the DMA request occurs, it should write into SPI's IFCR to clear the
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/// EOT flag to allow the next transmission.
fn address(&self) -> usize {
// Note(unsafe): It is assumed that SPI is owned by another DMA transfer and
// this DMA is only used for writing to the configuration registers.
let regs = unsafe { &*hal::stm32::$spi::ptr() };
&regs.ifcr as *const _ as usize
}
}
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/// 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::$spi, hal::spi::Disabled, u16>,
PeripheralToMemory,
&'static mut [u16; SAMPLE_BUFFER_SIZE],
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hal::dma::DBTransfer,
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>,
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trigger_transfer: Transfer<
hal::dma::dma::$trigger_stream<hal::stm32::DMA1>,
[< $spi CR >],
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MemoryToPeripheral,
&'static mut [u32; 1],
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hal::dma::DBTransfer,
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>,
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clear_transfer: Transfer<
hal::dma::dma::$clear_stream<hal::stm32::DMA1>,
[< $spi IFCR >],
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MemoryToPeripheral,
&'static mut [u32; 1],
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hal::dma::DBTransfer,
>,
}
impl $name {
/// Construct the ADC input channel.
///
/// # Args
/// * `spi` - The SPI interface used to communicate with the ADC.
/// * `trigger_stream` - The DMA stream used to trigger each ADC transfer by
/// writing a word into the SPI TX FIFO.
/// * `data_stream` - The DMA stream used to read samples received over SPI into a data buffer.
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/// * `clear_stream` - The DMA stream used to clear the EOT flag in the SPI peripheral.
/// * `trigger_channel` - The ADC sampling timer output compare channel for read triggers.
/// * `clear_channel` - The shadow sampling timer output compare channel used for
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/// clearing the SPI EOT flag.
pub fn new(
spi: hal::spi::Spi<hal::stm32::$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>,
clear_stream: hal::dma::dma::$clear_stream<hal::stm32::DMA1>,
trigger_channel: timers::tim2::$trigger_channel,
clear_channel: timers::tim3::$clear_channel,
) -> Self {
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// The flag clear DMA transfer always clears the EOT flag in the SPI
// peripheral. It has the highest priority to ensure it is completed before the
// transfer trigger.
let clear_config = DmaConfig::default()
.priority(Priority::VeryHigh)
.circular_buffer(true);
unsafe {
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SPI_EOT_CLEAR[0] = 1 << 3;
}
// Generate DMA events when the timer hits zero (roll-over). This must be before
// the trigger channel DMA occurs, as if the trigger occurs first, the
// transmission will not occur.
clear_channel.listen_dma();
clear_channel.to_output_compare(0);
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let clear_transfer: Transfer<
_,
_,
MemoryToPeripheral,
_,
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_,
> = Transfer::init(
clear_stream,
[< $spi IFCR >]::new(clear_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.
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unsafe { &mut SPI_EOT_CLEAR },
None,
clear_config,
);
// Generate DMA events when an output compare of the timer hits the specified
// value.
trigger_channel.listen_dma();
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trigger_channel.to_output_compare(2 + $index);
// The trigger stream constantly writes to the SPI CR1 using a static word
// (which is a static value to enable the SPI transfer). 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);
// Note(unsafe): This word is initialized once per ADC initialization to verify
// it is initialized properly.
unsafe {
// Write a binary code into the SPI control register to initiate a transfer.
SPI_START[0] = 0x201;
};
// Construct the trigger stream to write from memory to the peripheral.
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let trigger_transfer: Transfer<
_,
_,
MemoryToPeripheral,
_,
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_,
> = Transfer::init(
trigger_stream,
[< $spi CR >]::new(trigger_channel),
// Note(unsafe): Because this is a Memory->Peripheral transfer, this data is never
// actually modified. It technically only needs to be immutably borrowed, but the
// current HAL API only supports mutable borrows.
unsafe { &mut SPI_START },
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None,
trigger_config,
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);
// The data stream constantly reads from the SPI RX FIFO into a RAM buffer. The peripheral
// stalls reads of the SPI RX FIFO until data is available, so the DMA transfer completes
// after the requested number of samples have been collected. Note that only ADC1's (sic!)
// data stream is used to trigger a transfer completion interrupt.
let data_config = DmaConfig::default()
.memory_increment(true)
.transfer_complete_interrupt($index == 1)
.priority(Priority::VeryHigh);
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// 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);
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// The data transfer is always a transfer of data from the peripheral to a RAM
// buffer.
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let 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,
);
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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,
clear_transfer,
}
}
/// Enable the ADC DMA transfer sequence.
pub fn start(&mut self) {
self.transfer.start(|spi| {
spi.enable_dma_rx();
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spi.inner().cr2.modify(|_, w| w.tsize().bits(1));
spi.inner().cr1.modify(|_, w| w.spe().set_bit());
});
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self.clear_transfer.start(|_| {});
self.trigger_transfer.start(|_| {});
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}
/// 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) -> &[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();
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// Start the next transfer.
self.transfer.clear_interrupts();
let (prev_buffer, _, _) =
self.transfer.next_transfer(next_buffer).unwrap();
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// .unwrap_none() https://github.com/rust-lang/rust/issues/62633
self.next_buffer.replace(prev_buffer);
self.next_buffer.as_ref().unwrap()
}
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}
}
};
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}
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adc_input!(
Adc0Input, 0, Stream0, Stream1, Stream2, SPI2, Channel1, TIM2_CH1,
Channel1, TIM3_CH1
);
adc_input!(
Adc1Input, 1, Stream3, Stream4, Stream5, SPI3, Channel2, TIM2_CH2,
Channel2, TIM3_CH2
);