Merge #879

879: Improve ADC configuration options r=Dirbaio a=chemicstry

This smooths out a few rough edges with ADC:
- Make `Resolution::to_max_count()` pub for all ADC versions. Useful if performing conversion manually.
- `VREF` and `VREFINT` were convoluted. `VREF` is an external voltage reference used for all ADC conversions and it is exposed as a separate pin on large chips, while on smaller ones it is connected to `VDDA` internally. `VREFINT` is an internal voltage reference connected to one of the ADC channels and can be used to calculate unknown `VREF` voltage.
- Add a separate `VREF_DEFAULT_MV`, equal to 3.3V, which is the usual supply voltage and should work for most simple cases.
  - For an external voltage reference `set_vref()` can be used to set a known precise voltage.
  - If no voltage reference is present, `VREFINT` calibration can be used to calculate unknown `VREF` voltage. If I understand correctly, this is only implemented for `adc_v3` (L4?), but is not currently exposed (private). If someone is interested, this can be fixed in separate PR.

Co-authored-by: chemicstry <[email protected]>

1 files changed, 3 insertions, 3 deletions

diff --git a/examples/stm32h7/src/bin/adc.rs b/examples/stm32h7/src/bin/adc.rs
index ce73364c0..d8a5d23d7 100644
--- a/examples/stm32h7/src/bin/adc.rs
+++ b/examples/stm32h7/src/bin/adc.rs
@@ -28,11 +28,11 @@ async fn main(_spawner: Spawner, mut p: Peripherals) {
 
     adc.set_sample_time(SampleTime::Cycles32_5);
 
-    let mut vref_channel = adc.enable_vref();
+    let mut vrefint_channel = adc.enable_vrefint();
 
     loop {
-        let vref = adc.read_internal(&mut vref_channel);
-        info!("vref: {}", vref);
+        let vrefint = adc.read_internal(&mut vrefint_channel);
+        info!("vrefint: {}", vrefint);
         let measured = adc.read(&mut p.PC0);
         info!("measured: {}", measured);
         Timer::after(Duration::from_millis(500)).await;