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Simplifies the API by taking in the TIMER and PPI channels

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This commit is contained in:
huntc 2022-03-07 12:45:37 +11:00
parent 98bdac51fe
commit 3990f09b29
2 changed files with 59 additions and 59 deletions
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92
embassy-nrf/src/saadc.rs
View file

@ -10,7 +10,8 @@ use embassy_hal_common::unborrow;
use futures::future::poll_fn;
use crate::interrupt;
use crate::ppi::{Event, Task};
use crate::ppi::{ConfigurableChannel, Event, Ppi, Task};
use crate::timer::{Frequency, Instance as TimerInstance, Timer};
use crate::{pac, peripherals};
use pac::{saadc, SAADC};
@ -297,36 +298,67 @@ impl<'d, const N: usize> Saadc<'d, N> {
/// Continuous sampling with double buffers.
///
/// NOTE: It is important that the time spent within the callback supplied
/// does not exceed the time taken to acquire the samples into a single buffer.
/// You should measure the time taken by the callback and set the sample buffer
/// size accordingly. Exceeding this time can lead to the peripheral re-writing
/// the other buffer.
///
/// A task-driven approach to driving TASK_SAMPLE is expected. With a task
/// driven approach, multiple channels can be used.
///
/// In addition, the caller is responsible for triggering TASK_START in
/// relation to the previous one having ended (EVENTS_END). The the initial
/// TASKS_START is triggered by this method.
///
/// A closure is provided so that any required initialization such as starting
/// the sampling task can occur once the peripheral has been started.
/// A TIMER and two PPI peripherals are passed in so that precise sampling
/// can be attained. The sampling interval is expressed by selecting a
/// timer clock frequency to use along with a counter threshold to be reached.
/// For example, 1KHz can be achieved using a frequency of 1MHz and a counter
/// threshold of 1000.
///
/// A sampler closure is provided that receives the buffer of samples, noting
/// that the size of this buffer can be less than the original buffer's size.
/// A command is return from the closure that indicates whether the sampling
/// should continue or stop.
pub async fn run_task_sampler<I, S, const N0: usize>(
///
/// NOTE: The time spent within the callback supplied should not exceed the time
/// taken to acquire the samples into a single buffer. You should measure the
/// time taken by the callback and set the sample buffer size accordingly.
/// Exceeding this time can lead to samples becoming dropped.
pub async fn run_task_sampler<S, T: TimerInstance, const N0: usize>(
&mut self,
timer: &mut T,
ppi_ch1: &mut impl ConfigurableChannel,
ppi_ch2: &mut impl ConfigurableChannel,
frequency: Frequency,
sample_counter: u32,
bufs: &mut [[[i16; N]; N0]; 2],
init: I,
sampler: S,
) where
I: FnMut(),
S: FnMut(&[[i16; N]]) -> SamplerState,
{
self.run_sampler(bufs, None, init, sampler).await;
let r = Self::regs();
// We want the task start to effectively short with the last one ending so
// we don't miss any samples. It'd be great for the SAADC to offer a SHORTS
// register instead, but it doesn't, so we must use PPI.
let mut start_ppi = Ppi::new_one_to_one(
ppi_ch1,
Event::from_reg(&r.events_end),
Task::from_reg(&r.tasks_start),
);
start_ppi.enable();
let mut timer = Timer::new(timer);
timer.set_frequency(frequency);
timer.cc(0).write(sample_counter);
timer.cc(0).short_compare_clear();
let mut sample_ppi = Ppi::new_one_to_one(
ppi_ch2,
timer.cc(0).event_compare(),
Task::from_reg(&r.tasks_sample),
);
timer.start();
self.run_sampler(
bufs,
None,
|| {
sample_ppi.enable();
},
sampler,
)
.await;
}
async fn run_sampler<I, S, const N0: usize>(
@ -424,31 +456,13 @@ impl<'d, const N: usize> Saadc<'d, N> {
})
.await;
}
/// Return the end event for use with PPI
pub fn event_end(&self) -> Event {
let r = Self::regs();
Event::from_reg(&r.events_end)
}
/// Return the sample task for use with PPI
pub fn task_sample(&self) -> Task {
let r = Self::regs();
Task::from_reg(&r.tasks_sample)
}
/// Return the start task for use with PPI
pub fn task_start(&self) -> Task {
let r = Self::regs();
Task::from_reg(&r.tasks_start)
}
}
impl<'d> Saadc<'d, 1> {
/// Continuous sampling on a single channel with double buffers.
///
/// The internal clock is to be used with a sample rate expressed as a divisor of
/// 16MHz, ranging from 80..2047. For example, 1600 represnts a sample rate of 10KHz
/// 16MHz, ranging from 80..2047. For example, 1600 represents a sample rate of 10KHz
/// given 16_000_000 / 10_000_000 = 1600.
///
/// A sampler closure is provided that receives the buffer of samples, noting

26
examples/nrf/src/bin/saadc_continuous.rs
View file

@ -6,9 +6,8 @@
mod example_common;
use embassy::executor::Spawner;
use embassy::time::Duration;
use embassy_nrf::ppi::Ppi;
use embassy_nrf::saadc::{ChannelConfig, Config, Saadc, SamplerState};
use embassy_nrf::timer::{Frequency, Timer};
use embassy_nrf::timer::Frequency;
use embassy_nrf::{interrupt, Peripherals};
use example_common::*;
@ -27,21 +26,6 @@ async fn main(_spawner: Spawner, mut p: Peripherals) {
[channel_1_config, channel_2_config, channel_3_config],
);
// We want the task start to effectively short with the last one ending so
// we don't miss any samples. The Saadc will trigger the initial TASKS_START.
let mut start_ppi = Ppi::new_one_to_one(p.PPI_CH0, saadc.event_end(), saadc.task_start());
start_ppi.enable();
let mut timer = Timer::new(p.TIMER0);
timer.set_frequency(Frequency::F1MHz);
timer.cc(0).write(1000); // We want to sample at 1KHz
timer.cc(0).short_compare_clear();
let mut sample_ppi =
Ppi::new_one_to_one(p.PPI_CH1, timer.cc(0).event_compare(), saadc.task_sample());
timer.start();
// This delay demonstrates that starting the timer prior to running
// the task sampler is benign given the calibration that follows.
embassy::time::Timer::after(Duration::from_millis(500)).await;
@ -54,10 +38,12 @@ async fn main(_spawner: Spawner, mut p: Peripherals) {
saadc
.run_task_sampler(
&mut p.TIMER0,
&mut p.PPI_CH0,
&mut p.PPI_CH1,
Frequency::F1MHz,
1000, // We want to sample at 1KHz
&mut bufs,
|| {
sample_ppi.enable();
},
move |buf| {
// NOTE: It is important that the time spent within this callback
// does not exceed the time taken to acquire the 1500 samples we