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Merge #1024

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1024: stm32/adc: Remove voltage and temperature conversions r=Dirbaio a=GrantM11235

The current conversion utilities are confusing and a bit of a footgun. (Two out of the three examples got it wrong! They didn't measure vref at all, so all the conversions are completely wrong if vcca isn't 3.3v)

I think we should eventually have some sort of conversion utilities in the HAL, but for now I think it is best to just remove it and let the users do their own math.

cc `@chemicstry` 

Co-authored-by: Grant Miller <GrantM11235@gmail.com>
This commit is contained in:
bors[bot] 2022-10-26 19:44:06 +00:00 committed by GitHub
commit 7f499f3edc
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7 changed files with 50 additions and 104 deletions
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21
embassy-stm32/src/adc/f1.rs
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@ -86,7 +86,6 @@ pub use sample_time::SampleTime;
pub struct Adc<'d, T: Instance> {
sample_time: SampleTime,
calibrated_vdda: u32,
phantom: PhantomData<&'d mut T>,
}
@ -122,7 +121,6 @@ impl<'d, T: Instance> Adc<'d, T> {
Self {
sample_time: Default::default(),
calibrated_vdda: VDDA_CALIB_MV,
phantom: PhantomData,
}
}
@ -162,29 +160,10 @@ impl<'d, T: Instance> Adc<'d, T> {
Temperature {}
}
/// Calculates the system VDDA by sampling the internal VREF channel and comparing
/// to the expected value. If the chip's VDDA is not stable, run this before each ADC
/// conversion.
pub fn calibrate(&mut self, vref: &mut Vref) -> u32 {
let old_sample_time = self.sample_time;
self.sample_time = SampleTime::Cycles239_5;
let vref_samp = self.read(vref);
self.sample_time = old_sample_time;
self.calibrated_vdda = (ADC_MAX * VREF_INT) / u32::from(vref_samp);
self.calibrated_vdda
}
pub fn set_sample_time(&mut self, sample_time: SampleTime) {
self.sample_time = sample_time;
}
/// Convert a measurement to millivolts
pub fn to_millivolts(&self, sample: u16) -> u16 {
((u32::from(sample) * self.calibrated_vdda) / ADC_MAX) as u16
}
/// Perform a single conversion.
fn convert(&mut self) -> u16 {
unsafe {

23
embassy-stm32/src/adc/v2.rs
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@ -80,15 +80,6 @@ impl super::sealed::InternalChannel<ADC1> for Temperature {
}
impl Temperature {
/// Converts temperature sensor reading in millivolts to degrees celcius
pub fn to_celcius(sample_mv: u16) -> f32 {
// From 6.3.22 Temperature sensor characteristics
const V25: i32 = 760; // mV
const AVG_SLOPE: f32 = 2.5; // mV/C
(sample_mv as i32 - V25) as f32 / AVG_SLOPE + 25.0
}
/// Time needed for temperature sensor readings to stabilize
pub fn start_time_us() -> u32 {
10
@ -172,7 +163,6 @@ impl Prescaler {
pub struct Adc<'d, T: Instance> {
sample_time: SampleTime,
vref_mv: u32,
resolution: Resolution,
phantom: PhantomData<&'d mut T>,
}
@ -200,7 +190,6 @@ where
Self {
sample_time: Default::default(),
resolution: Resolution::default(),
vref_mv: VREF_DEFAULT_MV,
phantom: PhantomData,
}
}
@ -213,18 +202,6 @@ where
self.resolution = resolution;
}
/// Set VREF value in millivolts. This value is used for [to_millivolts()] sample conversion.
///
/// Use this if you have a known precise VREF (VDDA) pin reference voltage.
pub fn set_vref_mv(&mut self, vref_mv: u32) {
self.vref_mv = vref_mv;
}
/// Convert a measurement to millivolts
pub fn to_millivolts(&self, sample: u16) -> u16 {
((u32::from(sample) * self.vref_mv) / self.resolution.to_max_count()) as u16
}
/// Enables internal voltage reference and returns [VrefInt], which can be used in
/// [Adc::read_internal()] to perform conversion.
pub fn enable_vrefint(&self) -> VrefInt {

39
embassy-stm32/src/adc/v3.rs
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@ -205,7 +205,6 @@ pub use sample_time::SampleTime;
pub struct Adc<'d, T: Instance> {
sample_time: SampleTime,
vref_mv: u32,
resolution: Resolution,
phantom: PhantomData<&'d mut T>,
}
@ -244,7 +243,6 @@ impl<'d, T: Instance> Adc<'d, T> {
Self {
sample_time: Default::default(),
resolution: Resolution::default(),
vref_mv: VREF_DEFAULT_MV,
phantom: PhantomData,
}
}
@ -285,31 +283,6 @@ impl<'d, T: Instance> Adc<'d, T> {
Vbat {}
}
/// Calculates the system VDDA by sampling the internal VREFINT channel and comparing
/// the result with the value stored at the factory. If the chip's VDDA is not stable, run
/// this before each ADC conversion.
#[cfg(not(stm32g0))] // TODO is this supposed to be public?
#[allow(unused)] // TODO is this supposed to be public?
fn calibrate(&mut self, vrefint: &mut VrefInt) {
#[cfg(stm32l5)]
let vrefint_cal: u32 = todo!();
#[cfg(not(stm32l5))]
let vrefint_cal = unsafe { crate::pac::VREFINTCAL.data().read().value() };
let old_sample_time = self.sample_time;
// "Table 24. Embedded internal voltage reference" states that the sample time needs to be
// at a minimum 4 us. With 640.5 ADC cycles we have a minimum of 8 us at 80 MHz, leaving
// some headroom.
self.sample_time = SampleTime::Cycles640_5;
// This can't actually fail, it's just in a result to satisfy hal trait
let vrefint_samp = self.read(vrefint);
self.sample_time = old_sample_time;
self.vref_mv = (VREF_CALIB_MV * u32::from(vrefint_cal)) / u32::from(vrefint_samp);
}
pub fn set_sample_time(&mut self, sample_time: SampleTime) {
self.sample_time = sample_time;
}
@ -318,18 +291,6 @@ impl<'d, T: Instance> Adc<'d, T> {
self.resolution = resolution;
}
/// Set VREF value in millivolts. This value is used for [to_millivolts()] sample conversion.
///
/// Use this if you have a known precise VREF (VDDA) pin reference voltage.
pub fn set_vref_mv(&mut self, vref_mv: u32) {
self.vref_mv = vref_mv;
}
/// Convert a measurement to millivolts
pub fn to_millivolts(&self, sample: u16) -> u16 {
((u32::from(sample) * self.vref_mv) / self.resolution.to_max_count()) as u16
}
/*
/// Convert a raw sample from the `Temperature` to deg C
pub fn to_degrees_centigrade(sample: u16) -> f32 {

14
embassy-stm32/src/adc/v4.rs
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@ -314,7 +314,6 @@ impl Prescaler {
pub struct Adc<'d, T: Instance> {
sample_time: SampleTime,
vref_mv: u32,
resolution: Resolution,
phantom: PhantomData<&'d mut T>,
}
@ -352,7 +351,6 @@ impl<'d, T: Instance + crate::rcc::RccPeripheral> Adc<'d, T> {
let mut s = Self {
sample_time: Default::default(),
vref_mv: VREF_DEFAULT_MV,
resolution: Resolution::default(),
phantom: PhantomData,
};
@ -459,18 +457,6 @@ impl<'d, T: Instance + crate::rcc::RccPeripheral> Adc<'d, T> {
self.resolution = resolution;
}
/// Set VREF value in millivolts. This value is used for [to_millivolts()] sample conversion.
///
/// Use this if you have a known precise VREF (VDDA) pin reference voltage.
pub fn set_vref_mv(&mut self, vref_mv: u32) {
self.vref_mv = vref_mv;
}
/// Convert a measurement to millivolts
pub fn to_millivolts(&self, sample: u16) -> u16 {
((u32::from(sample) * self.vref_mv) / self.resolution.to_max_count()) as u16
}
/// Perform a single conversion.
fn convert(&mut self) -> u16 {
unsafe {

14
examples/stm32f1/src/bin/adc.rs
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@ -16,11 +16,19 @@ async fn main(_spawner: Spawner) {
let mut adc = Adc::new(p.ADC1, &mut Delay);
let mut pin = p.PB1;
let mut vref = adc.enable_vref(&mut Delay);
adc.calibrate(&mut vref);
let mut vrefint = adc.enable_vref(&mut Delay);
let vrefint_sample = adc.read(&mut vrefint);
let convert_to_millivolts = |sample| {
// From http://www.st.com/resource/en/datasheet/CD00161566.pdf
// 5.3.4 Embedded reference voltage
const VREFINT_MV: u32 = 1200; // mV
(u32::from(sample) * VREFINT_MV / u32::from(vrefint_sample)) as u16
};
loop {
let v = adc.read(&mut pin);
info!("--> {} - {} mV", v, adc.to_millivolts(v));
info!("--> {} - {} mV", v, convert_to_millivolts(v));
Timer::after(Duration::from_millis(100)).await;
}
}

31
examples/stm32f4/src/bin/adc.rs
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@ -24,19 +24,44 @@ async fn main(_spawner: Spawner) {
// Startup delay can be combined to the maximum of either
delay.delay_us(Temperature::start_time_us().max(VrefInt::start_time_us()));
let vrefint_sample = adc.read_internal(&mut vrefint);
let convert_to_millivolts = |sample| {
// From http://www.st.com/resource/en/datasheet/DM00071990.pdf
// 6.3.24 Reference voltage
const VREFINT_MV: u32 = 1210; // mV
(u32::from(sample) * VREFINT_MV / u32::from(vrefint_sample)) as u16
};
let convert_to_celcius = |sample| {
// From http://www.st.com/resource/en/datasheet/DM00071990.pdf
// 6.3.22 Temperature sensor characteristics
const V25: i32 = 760; // mV
const AVG_SLOPE: f32 = 2.5; // mV/C
let sample_mv = convert_to_millivolts(sample) as i32;
(sample_mv - V25) as f32 / AVG_SLOPE + 25.0
};
info!("VrefInt: {}", vrefint_sample);
const MAX_ADC_SAMPLE: u16 = (1 << 12) - 1;
info!("VCCA: {} mV", convert_to_millivolts(MAX_ADC_SAMPLE));
loop {
// Read pin
let v = adc.read(&mut pin);
info!("PC1: {} ({} mV)", v, adc.to_millivolts(v));
info!("PC1: {} ({} mV)", v, convert_to_millivolts(v));
// Read internal temperature
let v = adc.read_internal(&mut temp);
let celcius = Temperature::to_celcius(adc.to_millivolts(v));
let celcius = convert_to_celcius(v);
info!("Internal temp: {} ({} C)", v, celcius);
// Read internal voltage reference
let v = adc.read_internal(&mut vrefint);
info!("VrefInt: {} ({} mV)", v, adc.to_millivolts(v));
info!("VrefInt: {}", v);
Timer::after(Duration::from_millis(100)).await;
}

12
examples/stm32f7/src/bin/adc.rs
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@ -16,9 +16,19 @@ async fn main(_spawner: Spawner) {
let mut adc = Adc::new(p.ADC1, &mut Delay);
let mut pin = p.PA3;
let mut vrefint = adc.enable_vrefint();
let vrefint_sample = adc.read_internal(&mut vrefint);
let convert_to_millivolts = |sample| {
// From http://www.st.com/resource/en/datasheet/DM00273119.pdf
// 6.3.27 Reference voltage
const VREFINT_MV: u32 = 1210; // mV
(u32::from(sample) * VREFINT_MV / u32::from(vrefint_sample)) as u16
};
loop {
let v = adc.read(&mut pin);
info!("--> {} - {} mV", v, adc.to_millivolts(v));
info!("--> {} - {} mV", v, convert_to_millivolts(v));
Timer::after(Duration::from_millis(100)).await;
}
}