new PR, taking Dirbao's advice to make the DMA impl in a separate struct that consumes Adc<T> to make RingBufferedAdc<T>. Handling overrun similar to RingBufferedUart

1 files changed, 59 insertions, 0 deletions

diff --git a/examples/stm32f4/src/bin/adc_dma.rs b/examples/stm32f4/src/bin/adc_dma.rs
new file mode 100644
index 000000000..a2611bb6f
--- /dev/null
+++ b/examples/stm32f4/src/bin/adc_dma.rs
@@ -0,0 +1,59 @@
+#![no_std]
+#![no_main]
+use cortex_m::singleton;
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_stm32::adc::RingBufferedAdc;
+use embassy_stm32::adc::{Adc, SampleTime, Sequence};
+use embassy_time::{Instant, Timer};
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    const ADC_BUF_SIZE: usize = 1024;
+    let mut p = embassy_stm32::init(Default::default());
+
+    let adc_data: &mut [u16; ADC_BUF_SIZE] = singleton!(ADCDAT : [u16; ADC_BUF_SIZE] = [0u16; ADC_BUF_SIZE]).unwrap();
+    
+    let adc = Adc::new(p.ADC1);
+
+    let mut adc: RingBufferedAdc<embassy_stm32::peripherals::ADC1> = adc.into_ring_buffered(p.DMA2_CH0, adc_data);
+
+    adc.set_sample_sequence(Sequence::One, &mut p.PA0, SampleTime::CYCLES112);
+    adc.set_sample_sequence(Sequence::Two, &mut p.PA2, SampleTime::CYCLES112);
+    adc.set_sample_sequence(Sequence::Three, &mut p.PA1, SampleTime::CYCLES112);
+    adc.set_sample_sequence(Sequence::Four, &mut p.PA3, SampleTime::CYCLES112);
+
+    // Note that overrun is a big consideration in this implementation. Whatever task is running the adc.read() calls absolutely must circle back around
+    // to the adc.read() call before the DMA buffer is wrapped around > 1 time. At this point, the overrun is so significant that the context of
+    // what channel is at what index is lost. The buffer must be cleared and reset. This *is* handled here, but allowing this to happen will cause
+    // a reduction of performance as each time the buffer is reset, the adc & dma buffer must be restarted.
+
+    // An interrupt executor with a higher priority than other tasks may be a good approach here, allowing this task to wake and read the buffer most
+    // frequently.
+    let mut tic = Instant::now();
+    let mut buffer1: [u16; 256] = [0u16; 256];
+    let _ = adc.start();
+    loop {
+        match adc.read(&mut buffer1).await {
+            Ok(_data) => {
+                let toc = Instant::now();
+                info!(
+                    "\n adc1: {} dt = {}, n = {}",
+                    buffer1[0..16],
+                    (toc - tic).as_micros(),
+                    _data
+                );
+                tic = toc;
+            }
+            Err(e) => {
+                warn!("Error: {:?}", e);
+                buffer1 = [0u16; 256];
+                let _ = adc.start();
+                continue;
+            }
+        }
+
+        Timer::after_micros(300).await;
+    }
+}