added ADC example running on L0

examples/stm32l0/src/bin/adc.rs

@@ -0,0 +1,46 @@
+#![no_std]
+#![no_main]
+
+use defmt::*;
+use embassy_stm32::Config;
+use embassy_executor::Spawner;
+use embassy_stm32::adc::{Adc, SampleTime};
+use embassy_stm32::peripherals::ADC;
+use embassy_stm32::{adc, bind_interrupts};
+use embassy_time::{Delay, Timer};
+use {defmt_rtt as _, panic_probe as _};
+
+bind_interrupts!(struct Irqs {
+    ADC1_COMP => adc::InterruptHandler<ADC>;
+});
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    // enable HSI because default is MSI but ADC doesn't support
+    // this as clock source on L0s and uses HSI by default
+    let mut config = Config::default();
+    config.rcc.hsi = true;
+    let p = embassy_stm32::init(config);
+
+    info!("Hello World!");
+
+    let mut adc = Adc::new(p.ADC, Irqs, &mut Delay);
+    adc.set_sample_time(SampleTime::Cycles79_5);
+    let mut pin = p.PA1;
+
+    let mut vrefint = adc.enable_vref(&mut Delay);
+    let vrefint_sample = adc.read(&mut vrefint).await;
+    let convert_to_millivolts = |sample| {
+        // From https://www.st.com/resource/en/datasheet/stm32l051c6.pdf
+        // 6.3.3 Embedded internal reference voltage
+        const VREFINT_MV: u32 = 1224; // mV
+
+        (u32::from(sample) * VREFINT_MV / u32::from(vrefint_sample)) as u16
+    };
+
+    loop {
+        let v = adc.read(&mut pin).await;
+        info!("--> {} - {} mV", v, convert_to_millivolts(v));
+        Timer::after_millis(100).await;
+    }
+}