Merge #1024

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 <[email protected]>

1 files changed, 11 insertions, 1 deletions

diff --git a/examples/stm32f7/src/bin/adc.rs b/examples/stm32f7/src/bin/adc.rs
index 80fad8c41..70b3b2a75 100644
--- a/examples/stm32f7/src/bin/adc.rs
+++ b/examples/stm32f7/src/bin/adc.rs
@@ -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;
     }
 }