Decouple analog read from display refresh and add moving average

src/main.rs

@@ -5,7 +5,7 @@ use panic_halt as _;
 
 use fugit::RateExtU32;
 
-use cortex_m::prelude::{_embedded_hal_watchdog_Watchdog, _embedded_hal_watchdog_WatchdogEnable};
+use cortex_m::prelude::_embedded_hal_watchdog_Watchdog;
 use embedded_hal::adc::OneShot;
 use hal::i2c;
 pub use sparkfun_pro_micro_rp2040::hal;
@@ -23,16 +23,17 @@ use fugit::MicrosDurationU32;
 use hal::gpio::bank0::{Gpio14, Gpio15};
 use hal::gpio::Pin;
 use hal::pac::I2C1;
-use hal::timer::Alarm;
-use hal::timer::Alarm0;
+use hal::timer::{Alarm, Alarm0, Alarm1};
 use hal::Adc;
 
 const XTAL_FREQ_HZ: u32 = 12_000_000u32;
+const MVG_AVG_COUNT: u16 = 20;
 
 #[rtic::app(device = sparkfun_pro_micro_rp2040::hal::pac, peripherals = true)]
 mod app {
 
-    const CHANGE_FREQUENCY_TICKS: u32 = 500_000;
+    const DISPLAY_UPDATE_INT_TICKS: u32 = 500_000;
+    const SENSOR_READ_INT_TICKS: u32 = 50_000;
 
     use super::*;
     type Display = Ssd1306<
@@ -51,7 +52,9 @@ mod app {
 
     #[shared]
     struct Shared {
-        alarm: Alarm0,
+        alarm0: Alarm0,
+        alarm1: Alarm1,
+        sensor_value: u16,
     }
 
     #[local]
@@ -87,9 +90,13 @@ mod app {
             &mut resets,
         );
         let mut timer = hal::Timer::new(c.device.TIMER, &mut resets);
-        let mut alarm = timer.alarm_0().unwrap();
-        let _ = alarm.schedule(MicrosDurationU32::from_ticks(CHANGE_FREQUENCY_TICKS));
-        alarm.enable_interrupt();
+        let mut alarm0 = timer.alarm_0().unwrap();
+        let _ = alarm0.schedule(MicrosDurationU32::from_ticks(DISPLAY_UPDATE_INT_TICKS));
+        alarm0.enable_interrupt();
+
+        let mut alarm1 = timer.alarm_1().unwrap();
+        let _ = alarm1.schedule(MicrosDurationU32::from_ticks(SENSOR_READ_INT_TICKS));
+        alarm1.enable_interrupt();
 
         let scl = pins.gpio15.into_mode();
         let sda = pins.gpio14.into_mode();
@@ -120,7 +127,11 @@ mod app {
         let adc_pin = pins.gpio29.into_floating_input();
 
         (
-            Shared { alarm },
+            Shared {
+                alarm0,
+                alarm1,
+                sensor_value: 0,
+            },
             Local {
                 display,
                 adc,
@@ -131,19 +142,17 @@ mod app {
         )
     }
 
-    #[task(binds = TIMER_IRQ_0, priority = 1, shared = [alarm], local = [display, adc, adc_pin, watchdog])]
-    fn tick(mut c: tick::Context) {
-        use numtoa::NumToA;
-        let display = c.local.display;
-        display.clear();
+    #[task(binds = TIMER_IRQ_0, priority = 1, shared = [alarm0, sensor_value], local = [display])]
+    fn update_display(mut c: update_display::Context) {
         let mut buf = [0u8; 20];
-        let result: Result<u16, _> = c.local.adc.read(c.local.adc_pin);
 
-        let text = match result {
-            Ok(reading_raw) => reading_raw.numtoa_str(10, &mut buf),
-            Err(_) => "Error",
-        };
+        let text = c.shared.sensor_value.lock(|val| {
+            use numtoa::NumToA;
+            val.numtoa_str(10, &mut buf)
+        });
 
+        let display = c.local.display;
+        display.clear();
         Text::with_alignment(
             text,
             display.bounding_box().center(),
@@ -153,11 +162,24 @@ mod app {
         .draw(display)
         .unwrap();
         display.flush().unwrap();
-        c.local.watchdog.feed();
 
-        c.shared.alarm.lock(|a| {
+        c.shared.alarm0.lock(|a| {
+            a.clear_interrupt();
+            let _ = a.schedule(MicrosDurationU32::from_ticks(DISPLAY_UPDATE_INT_TICKS));
+        });
+    }
+
+    #[task(binds = TIMER_IRQ_1, priority = 2, shared = [alarm1, sensor_value], local = [adc, adc_pin, watchdog])]
+    fn read_sensor(mut c: read_sensor::Context) {
+        let sensor_value: u16 = c.local.adc.read(c.local.adc_pin).unwrap();
+        c.shared
+            .sensor_value
+            .lock(|v| *v = (*v * (MVG_AVG_COUNT - 1) + sensor_value) / MVG_AVG_COUNT);
+
+        c.local.watchdog.feed();
+        c.shared.alarm1.lock(|a| {
             a.clear_interrupt();
-            let _ = a.schedule(MicrosDurationU32::from_ticks(CHANGE_FREQUENCY_TICKS));
+            let _ = a.schedule(MicrosDurationU32::from_ticks(DISPLAY_UPDATE_INT_TICKS));
         });
     }