ADC: Implement calibration

Author: mattico

examples/adc.rs

@@ -17,13 +17,17 @@ use rt::entry;
 #[entry]
 fn main() -> ! {
     let dp = stm32::Peripherals::take().expect("cannot take peripherals");
+    let cp = stm32::CorePeripherals::take().expect("cannot take core peripherals");
     let mut rcc = dp.RCC.constrain();
+    let mut delay = cp.SYST.delay(&mut rcc);
 
     let gpioa = dp.GPIOA.split(&mut rcc);
 
     let mut adc = dp.ADC.constrain(&mut rcc);
     adc.set_sample_time(SampleTime::T_80);
     adc.set_precision(Precision::B_12);
+    delay.delay(20.us()); // Wait for ADC voltage regulator to stabilize
+    adc.calibrate();
 
     let mut adc_pin = gpioa.pa0.into_analog();
     let mut vtemp = VTemp::new();

src/analog/adc.rs

@@ -68,6 +68,17 @@ impl Adc {
         }
     }
 
+    /// Runs the calibration routine on the ADC
+    ///
+    /// Wait for tADCVREG_SETUP (20us on STM32G071x8) after calling `new()`
+    /// before calibrating, to wait for the ADC voltage regulator to stabilize.
+    ///
+    /// Do not call if an ADC reading is ongoing.
+    pub fn calibrate(&mut self) {
+        self.rb.cr.modify(|_, w| w.adcal().set_bit());
+        while self.rb.cr.read().adcal().bit_is_set() {}
+    }
+
     /// Set the Adc sampling time
     pub fn set_sample_time(&mut self, t_samp: SampleTime) {
         self.sample_time = t_samp;