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refactor: try to read the temperature but smarter

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This commit is contained in:
cscherr 2025-04-28 17:20:36 +02:00
parent f6d7a67683
commit 7d4770dc9e
Signed by: cscherrNT
GPG key ID: 8E2B45BC51A27EA7
1 changed files with 56 additions and 24 deletions
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80
examples/temperature.rs
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@ -1,10 +1,11 @@
// NOTE: This is at least unreliable and likely wrong
#![no_main]
#![no_std]
use defmt::info;
use hal::adc::{Adc, Ready, VTemp};
use hal::gpio::Analog;
use hal::gpio::gpiob::PB1;
use defmt::{debug, info};
use hal::adc::{Adc, Ready, VRef, VTemp};
use hal::calibration::{VtempCal30, VtempCal130};
use panic_probe as _;
use defmt_rtt as _; // global logger
@ -12,8 +13,6 @@ use defmt_rtt as _; // global logger
use cortex_m_rt::entry;
use hal::{pac, prelude::*, rcc::Config};
const MAGIC_TEMPERATURE_NUMBER: f32 = 12.412122;
#[entry]
fn main() -> ! {
let dp = pac::Peripherals::take().unwrap();
@ -22,28 +21,61 @@ fn main() -> ! {
let mut rcc = dp.RCC.freeze(Config::hsi16());
let mut adc = dp.ADC.constrain(&mut rcc);
let gpiob = dp.GPIOB.split(&mut rcc);
let mut temp_pin = gpiob.pb1.into_analog();
// Get the delay provider.
let mut delay = cp.SYST.delay(rcc.clocks);
let mut temp;
let mut i = 0;
// manual says i need to calibrate but then boom
adc.set_sample_time(hal::adc::SampleTime::T_1_5);
delay.delay_ms(50_u16);
adc.calibrate().unwrap();
delay.delay_ms(5000_u16);
// NOTE: TSEN bit must be enabled for reading the temperature
VTemp.enable(&mut adc);
// reference temperatures from the chips readonly memory
// [Source](https://www.st.com/resource/en/datasheet/stm32l053r8.pdf),
// Table 6 in Secion 3.13 "Temperature sensor"
//
// More and better info in the large 1000+ page sheet "Ultra-low-power
// STM32L0x3 advanced Arm®-based 32-bit MCUs" (RM0367), 14.9
//
// This is basically calibration data
info!(
"reading calibration data... If this is the last thing you hear from me something has gone terribly wrong"
);
let vref_cal = hal::calibration::VrefintCal::get().read();
let tsense_cal1 = (30, VtempCal30::get().read());
let tsense_cal2 = (130, VtempCal130::get().read());
info!("tsense_cal1: {:?}", (30, tsense_cal1));
info!("tsense_cal2: {:?}", (130, tsense_cal2));
delay.delay_ms(50_u16);
let vref_actual: u16 = adc.read(&mut VRef).unwrap();
let vref_factor = vref_cal as f32 / vref_actual as f32;
debug!(
"vref real={} register={} => factor={}",
vref_actual, vref_cal, vref_factor
);
let mut temp_c;
let mut temp_mv;
loop {
if i % 10_000 == 0 {
temp = read_temp_c(&mut temp_pin, &mut adc);
info!("Temperature: {}", temp);
}
// delay.delay_ms(200_u16);
i += 1;
temp_mv = read_temp_mv(&mut adc, vref_factor);
temp_c = temp_mv_to_c(temp_mv, tsense_cal1, tsense_cal2);
info!("Temperature: {:03}mv, {:04}c", temp_mv, temp_c as i32);
delay.delay_ms(500_u16);
}
}
fn read_temp_c(pin: &mut PB1<Analog>, adc: &mut Adc<Ready>) -> i16 {
let v: f32 = adc
.read(pin /* or maybe VTemp from the adc module? */)
.expect("could not read with adc");
(v / MAGIC_TEMPERATURE_NUMBER) as i16 - 50
fn read_temp_mv(adc: &mut Adc<Ready>, vref_factor: f32) -> f32 {
let bare: f32 = adc.read(&mut VTemp).expect("could not read with adc");
bare * vref_factor
}
// This unholy abomination is from the datasheet and does not actually look so bad if it's written
// in Math instead of Rust.
fn temp_mv_to_c(temp: f32, ts_cal_1: (i32, u16), ts_cal_2: (i32, u16)) -> f32 {
((ts_cal_2.0 as f32 - ts_cal_1.0 as f32) / (ts_cal_2.1 as f32 - ts_cal_1.1 as f32))
* (temp - ts_cal_1.1 as f32)
+ ts_cal_1.0 as f32
}