1 files changed, 18 insertions, 8 deletions
diff --git a/embassy-stm32/src/adc/v2.rs b/embassy-stm32/src/adc/v2.rs
index 5c608451..a74c0097 100644
--- a/embassy-stm32/src/adc/v2.rs
+++ b/embassy-stm32/src/adc/v2.rs
@@ -7,7 +7,10 @@ use crate::adc::{AdcPin, Instance};
 use crate::time::Hertz;
 use crate::Peripheral;
 
-pub const VDDA_CALIB_MV: u32 = 3000;
+/// Default VREF voltage used for sample conversion to millivolts.
+pub const VREF_DEFAULT_MV: u32 = 3300;
+/// VREF voltage used for factory calibration of VREFINTCAL register.
+pub const VREF_CALIB_MV: u32 = 3300;
 
 #[cfg(not(any(rcc_f4, rcc_f7)))]
 fn enable() {
@@ -47,7 +50,7 @@ impl Resolution {
         }
     }
 
-    fn to_max_count(&self) -> u32 {
+    pub fn to_max_count(&self) -> u32 {
         match self {
             Resolution::TwelveBit => (1 << 12) - 1,
             Resolution::TenBit => (1 << 10) - 1,
@@ -57,9 +60,9 @@ impl Resolution {
     }
 }
 
-pub struct Vref;
-impl<T: Instance> AdcPin<T> for Vref {}
-impl<T: Instance> super::sealed::AdcPin<T> for Vref {
+pub struct VrefInt;
+impl<T: Instance> AdcPin<T> for VrefInt {}
+impl<T: Instance> super::sealed::AdcPin<T> for VrefInt {
     fn channel(&self) -> u8 {
         17
     }
@@ -150,7 +153,7 @@ impl Prescaler {
 
 pub struct Adc<'d, T: Instance> {
     sample_time: SampleTime,
-    calibrated_vdda: u32,
+    vref: u32,
     resolution: Resolution,
     phantom: PhantomData<&'d mut T>,
 }
@@ -180,7 +183,7 @@ where
         Self {
             sample_time: Default::default(),
             resolution: Resolution::default(),
-            calibrated_vdda: VDDA_CALIB_MV,
+            vref: VREF_DEFAULT_MV,
             phantom: PhantomData,
         }
     }
@@ -193,9 +196,16 @@ where
         self.resolution = resolution;
     }
 
+    /// Set VREF, which is used for [to_millivolts()] conversion.
+    ///
+    /// Use this if you have a known precise VREF (VDDA) pin reference voltage.
+    pub fn set_vref(&mut self, vref: u32) {
+        self.vref = vref;
+    }
+
     /// Convert a measurement to millivolts
     pub fn to_millivolts(&self, sample: u16) -> u16 {
-        ((u32::from(sample) * self.calibrated_vdda) / self.resolution.to_max_count()) as u16
+        ((u32::from(sample) * self.vref) / self.resolution.to_max_count()) as u16
     }
 
     /// Perform a single conversion.