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Extend SAADC one shot support

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One-shot mode now permits the sampling of differential pins, and the sampling of multiple pins simultaneously.

A new ChannelConfig structure has been introduced so that multiple channels can be configured individually. Further, the `sample` method now accepts a buffer into which samples are written.

Along the way, I've reset some default configuration to align with Nordic's settings in their nrfx saadc driver. Specifically, the channel gain defaults to 6 (from 4) and the time defaults to 10us (from 20us).
This commit is contained in:
huntc 2021-10-07 18:00:03 +11:00
parent 009b77c1b9
commit cef6158c31
3 changed files with 145 additions and 44 deletions
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2
README.md
View file

@ -35,6 +35,8 @@ The `embassy-nrf` crate contains implementations for nRF 52 series SoCs.
- `uarte`: UARTE driver implementing `AsyncBufRead` and `AsyncWrite`.
- `qspi`: QSPI driver implementing `Flash`.
- `gpiote`: GPIOTE driver. Allows `await`ing GPIO pin changes. Great for reading buttons or receiving interrupts from external chips.
- `saadc`: SAADC driver. Provides a full implementation of the one-shot sampling for analog channels.
- `rtc`: RTC driver implementing `Clock` and `Alarm`, for use with `embassy::executor`.
## Examples

177
embassy-nrf/src/saadc.rs
View file

@ -1,3 +1,4 @@
use core::convert::TryInto;
use core::marker::PhantomData;
use core::sync::atomic::{compiler_fence, Ordering};
use core::task::Poll;
@ -15,6 +16,7 @@ use pac::{saadc, SAADC};
pub use saadc::{
ch::{
config::{GAIN_A as Gain, REFSEL_A as Reference, RESP_A as Resistor, TACQ_A as Time},
pseln::PSELN_A as NegativeChannel,
pselp::PSELP_A as PositiveChannel,
},
oversample::OVERSAMPLE_A as Oversample,
@ -27,7 +29,7 @@ pub use saadc::{
pub enum Error {}
/// One-shot saadc. Continuous sample mode TODO.
pub struct OneShot<'d> {
pub struct OneShot<'d, const N: usize> {
phantom: PhantomData<&'d mut peripherals::SAADC>,
}
@ -36,11 +38,29 @@ static WAKER: AtomicWaker = AtomicWaker::new();
/// Used to configure the SAADC peripheral.
///
/// See the `Default` impl for suitable default values.
#[non_exhaustive]
pub struct Config {
/// Output resolution in bits.
pub resolution: Resolution,
/// Average 2^`oversample` input samples before transferring the result into memory.
pub oversample: Oversample,
}
impl Default for Config {
/// Default configuration for single channel sampling.
fn default() -> Self {
Self {
resolution: Resolution::_14BIT,
oversample: Oversample::BYPASS,
}
}
}
/// Used to configure an individual SAADC peripheral channel.
///
/// See the `Default` impl for suitable default values.
#[non_exhaustive]
pub struct ChannelConfig {
/// Reference voltage of the SAADC input.
pub reference: Reference,
/// Gain used to control the effective input range of the SAADC.
@ -49,26 +69,48 @@ pub struct Config {
pub resistor: Resistor,
/// Acquisition time in microseconds.
pub time: Time,
/// Positive channel to sample
p_channel: PositiveChannel,
/// An optional negative channel to sample
n_channel: Option<NegativeChannel>,
}
impl Default for Config {
fn default() -> Self {
impl ChannelConfig {
/// Default configuration for single ended channel sampling.
pub fn single_ended(pin: impl Unborrow<Target = impl PositivePin>) -> Self {
unborrow!(pin);
Self {
resolution: Resolution::_14BIT,
oversample: Oversample::OVER8X,
reference: Reference::VDD1_4,
gain: Gain::GAIN1_4,
reference: Reference::INTERNAL,
gain: Gain::GAIN1_6,
resistor: Resistor::BYPASS,
time: Time::_20US,
time: Time::_10US,
p_channel: pin.channel(),
n_channel: None,
}
}
/// Default configuration for differential channel sampling.
pub fn differential(
ppin: impl Unborrow<Target = impl PositivePin>,
npin: impl Unborrow<Target = impl NegativePin>,
) -> Self {
unborrow!(ppin, npin);
Self {
reference: Reference::VDD1_4,
gain: Gain::GAIN1_6,
resistor: Resistor::BYPASS,
time: Time::_10US,
p_channel: ppin.channel(),
n_channel: Some(npin.channel()),
}
}
}
impl<'d> OneShot<'d> {
impl<'d, const N: usize> OneShot<'d, N> {
pub fn new(
_saadc: impl Unborrow<Target = peripherals::SAADC> + 'd,
irq: impl Unborrow<Target = interrupt::SAADC> + 'd,
config: Config,
channel_configs: [ChannelConfig; N],
) -> Self {
unborrow!(irq);
@ -77,31 +119,37 @@ impl<'d> OneShot<'d> {
let Config {
resolution,
oversample,
reference,
gain,
resistor,
time,
} = config;
// Configure pins
// Configure channels
r.enable.write(|w| w.enable().enabled());
r.resolution.write(|w| w.val().variant(resolution));
r.oversample.write(|w| w.oversample().variant(oversample));
r.ch[0].config.write(|w| {
w.refsel().variant(reference);
w.gain().variant(gain);
w.tacq().variant(time);
w.mode().se();
w.resp().variant(resistor);
w.resn().bypass();
if !matches!(oversample, Oversample::BYPASS) {
w.burst().enabled();
} else {
w.burst().disabled();
for (i, cc) in channel_configs.iter().enumerate() {
r.ch[i].pselp.write(|w| w.pselp().variant(cc.p_channel));
if let Some(npin) = cc.n_channel.as_ref() {
r.ch[i].pseln.write(|w| w.pseln().variant(*npin));
}
w
});
r.ch[i].config.write(|w| {
w.refsel().variant(cc.reference);
w.gain().variant(cc.gain);
w.tacq().variant(cc.time);
if cc.n_channel.is_none() {
w.mode().se();
} else {
w.mode().diff();
}
w.resp().variant(cc.resistor);
w.resn().bypass();
if !matches!(oversample, Oversample::BYPASS) {
w.burst().enabled();
} else {
w.burst().disabled();
}
w
});
}
// Disable all events interrupts
r.intenclr.write(|w| unsafe { w.bits(0x003F_FFFF) });
@ -128,18 +176,16 @@ impl<'d> OneShot<'d> {
unsafe { &*SAADC::ptr() }
}
pub async fn sample(&mut self, pin: &mut impl PositivePin) -> i16 {
pub async fn sample(&mut self, buf: &mut [i16; N]) {
let r = Self::regs();
// Set positive channel
r.ch[0].pselp.write(|w| w.pselp().variant(pin.channel()));
// Set up the DMA
let mut val: i16 = 0;
r.result
.ptr
.write(|w| unsafe { w.ptr().bits(((&mut val) as *mut _) as u32) });
r.result.maxcnt.write(|w| unsafe { w.maxcnt().bits(1) });
.write(|w| unsafe { w.ptr().bits(buf.as_mut_ptr() as u32) });
r.result
.maxcnt
.write(|w| unsafe { w.maxcnt().bits(N.try_into().unwrap()) });
// Reset and enable the end event
r.events_end.reset();
@ -166,13 +212,10 @@ impl<'d> OneShot<'d> {
Poll::Pending
})
.await;
// The DMA wrote the sampled value to `val`.
val
}
}
impl<'d> Drop for OneShot<'d> {
impl<'d, const N: usize> Drop for OneShot<'d, N> {
fn drop(&mut self) {
let r = Self::regs();
r.enable.write(|w| w.enable().disabled());
@ -180,8 +223,6 @@ impl<'d> Drop for OneShot<'d> {
}
/// A pin that can be used as the positive end of a ADC differential in the SAADC periperhal.
///
/// Currently negative is always shorted to ground (0V).
pub trait PositivePin {
fn channel(&self) -> PositiveChannel;
}
@ -198,6 +239,38 @@ macro_rules! positive_pin_mappings {
};
}
/// A pin that can be used as the negative end of a ADC differential in the SAADC periperhal.
pub trait NegativePin {
fn channel(&self) -> NegativeChannel;
}
macro_rules! negative_pin_mappings {
( $($ch:ident => $pin:ident,)*) => {
$(
impl NegativePin for crate::peripherals::$pin {
fn channel(&self) -> NegativeChannel {
NegativeChannel::$ch
}
}
)*
};
}
/// Represents an unconnected pin
pub struct NotConnected {}
impl PositivePin for NotConnected {
fn channel(&self) -> PositiveChannel {
PositiveChannel::NC
}
}
impl NegativePin for NotConnected {
fn channel(&self) -> NegativeChannel {
NegativeChannel::NC
}
}
// TODO the variant names are unchecked
// the pins are copied from nrf hal
#[cfg(feature = "9160")]
@ -223,3 +296,27 @@ positive_pin_mappings! {
ANALOGINPUT6 => P0_30,
ANALOGINPUT7 => P0_31,
}
#[cfg(feature = "9160")]
negative_pin_mappings! {
ANALOGINPUT0 => P0_13,
ANALOGINPUT1 => P0_14,
ANALOGINPUT2 => P0_15,
ANALOGINPUT3 => P0_16,
ANALOGINPUT4 => P0_17,
ANALOGINPUT5 => P0_18,
ANALOGINPUT6 => P0_19,
ANALOGINPUT7 => P0_20,
}
#[cfg(not(feature = "9160"))]
negative_pin_mappings! {
ANALOGINPUT0 => P0_02,
ANALOGINPUT1 => P0_03,
ANALOGINPUT2 => P0_04,
ANALOGINPUT3 => P0_05,
ANALOGINPUT4 => P0_28,
ANALOGINPUT5 => P0_29,
ANALOGINPUT6 => P0_30,
ANALOGINPUT7 => P0_31,
}

10
examples/nrf/src/bin/saadc.rs
View file

@ -7,18 +7,20 @@ mod example_common;
use defmt::panic;
use embassy::executor::Spawner;
use embassy::time::{Duration, Timer};
use embassy_nrf::saadc::{Config, OneShot};
use embassy_nrf::saadc::{ChannelConfig, Config, OneShot};
use embassy_nrf::{interrupt, Peripherals};
use example_common::*;
#[embassy::main]
async fn main(_spawner: Spawner, mut p: Peripherals) {
let config = Config::default();
let mut saadc = OneShot::new(p.SAADC, interrupt::take!(SAADC), config);
let channel_config = ChannelConfig::single_ended(&mut p.P0_02);
let mut saadc = OneShot::new(p.SAADC, interrupt::take!(SAADC), config, [channel_config]);
loop {
let sample = saadc.sample(&mut p.P0_02).await;
info!("sample: {=i16}", sample);
let mut buf = [0; 1];
saadc.sample(&mut buf).await;
info!("sample: {=i16}", &buf[0]);
Timer::after(Duration::from_millis(100)).await;
}
}