Separate sensor read into a separate task

Cargo.lock

@@ -800,12 +800,14 @@ name = "pico-enviro-sensor"
 version = "0.1.0"
 dependencies = [
  "cortex-m-rt",
- "critical-section",
+ "embassy-embedded-hal",
  "embassy-executor",
  "embassy-rp",
+ "embassy-sync",
  "embassy-time",
  "rtt-target",
  "scd4x",
+ "static_cell",
 ]
 
 [[package]]
@@ -1038,7 +1040,7 @@ checksum = "f7c45b9784283f1b2e7fb61b42047c2fd678ef0960d4f6f1eba131594cc369d4"
 [[package]]
 name = "scd4x"
 version = "0.4.0"
-source = "git+https://github.com/twokilohertz/scd4x-rs.git?branch=main#b9b0cb774b78ec7317c3e66f2fae745711101abb"
+source = "git+https://github.com/twokilohertz/scd4x-rs.git?branch=conversion-fixes#07730523c51d6909530c000de271832125760385"
 dependencies = [
  "embedded-hal 1.0.0",
  "log",
@@ -1117,6 +1119,15 @@ version = "1.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a8f112729512f8e442d81f95a8a7ddf2b7c6b8a1a6f509a95864142b30cab2d3"
 
+[[package]]
+name = "static_cell"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d89b0684884a883431282db1e4343f34afc2ff6996fe1f4a1664519b66e14c1e"
+dependencies = [
+ "portable-atomic",
+]
+
 [[package]]
 name = "string_cache"
 version = "0.8.8"

Cargo.toml

@@ -22,14 +22,16 @@ embassy-executor = { version = "0.7.0", features = [
     "task-arena-size-65536",
 ] }
 embassy-time = "0.4.0"
+embassy-sync = "0.6.2"
+embassy-embedded-hal = "0.3.0"
+static_cell = "2.1.0"
 
 # System
 cortex-m-rt = "0.7.5"
-critical-section = "1.2.0"
 rtt-target = "0.6.1"
 
 # Peripherals
-scd4x = { git = "https://github.com/twokilohertz/scd4x-rs.git", branch = "main", features = [
+scd4x = { git = "https://github.com/twokilohertz/scd4x-rs.git", branch = "conversion-fixes", features = [
     "scd41",
 ] }
 

src/main.rs

@@ -1,20 +1,29 @@
 #![no_std]
 #![no_main]
 
+mod sensor_task;
+
+use core::cell::RefCell;
+
 use rtt_target::{rprintln, rtt_init_print};
 
 use embassy_executor::Spawner;
-use embassy_rp::block::ImageDef;
+use embassy_rp::{block::ImageDef, i2c::Blocking, i2c::I2c, peripherals::I2C0};
+use embassy_sync::blocking_mutex::{raw::NoopRawMutex, Mutex};
+use embassy_time::Timer;
+use static_cell::StaticCell;
 
-mod sensor_task;
+use sensor_task::sensor_read_task;
 
 embassy_rp::bind_interrupts!(struct Irqs {
     I2C0_IRQ => embassy_rp::i2c::InterruptHandler<embassy_rp::peripherals::I2C0>;
 });
 
+type I2c0BusType = Mutex<NoopRawMutex, RefCell<I2c<'static, I2C0, Blocking>>>;
+
 /// Entrypoint
 #[embassy_executor::main]
-async fn main(_spawner: Spawner) {
+async fn main(spawner: Spawner) {
     // Initialise RTT logging
 
     rtt_init_print!();
@@ -22,52 +31,19 @@ async fn main(_spawner: Spawner) {
 
     let peripherals = embassy_rp::init(Default::default());
 
+    // Initialise I2C0 on pins 4 & 5 for the SCD41 sensor
     let sda = peripherals.PIN_4;
     let scl = peripherals.PIN_5;
-    let mut i2c_config = embassy_rp::i2c::Config::default(); // TODO: Frequency is 100 MHz by default, should be 400 MHz
+    let mut i2c_config = embassy_rp::i2c::Config::default();
-    i2c_config.frequency = 400_000u32;
+    i2c_config.frequency = 400_000u32; // 400 kHz
     let i2c_bus = embassy_rp::i2c::I2c::new_blocking(peripherals.I2C0, scl, sda, i2c_config);
+    static I2C0_BUS: StaticCell<I2c0BusType> = StaticCell::new();
+    let shared_i2c0_bus = I2C0_BUS.init(Mutex::new(RefCell::new(i2c_bus)));
 
-    embassy_time::Timer::after_millis(30).await; // SCD41 power-up delay
+    spawner.must_spawn(sensor_read_task(shared_i2c0_bus));
-    let mut scd41 = scd4x::Scd4x::new(i2c_bus, embassy_time::Delay);
-    scd41.wake_up();
-    scd41.reinit().unwrap();
-
-    match scd41.serial_number() {
-        Ok(serial) => rprintln!("[SCD41] Serial number: {}", serial),
-        Err(error) => rprintln!(
-            "[SCD41] Error: did not respond to get_serial_number: {:?}",
-            error
-        ),
-    }
-
-    scd41.start_periodic_measurement().unwrap();
 
     loop {
-        embassy_time::Timer::after_secs(5).await;
+        Timer::after_secs(1).await;
-        match scd41.measurement() {
-            Ok(data) => {
-                rprintln!(
-                    "[SCD41] CO2: {} ppm, temperature: {} C, humidity: {} RH",
-                    data.co2,
-                    data.temperature,
-                    data.humidity
-                );
-            }
-            Err(error) => {
-                rprintln!(
-                    "[SCD41] Error: failed to retrieve measurement data: {:?}",
-                    error
-                );
-                break;
-            }
-        }
-    }
-
-    loop {
-        unsafe {
-            core::arch::asm!("wfi");
-        }
     }
 }
 

src/sensor_task.rs

@@ -0,0 +1,53 @@
+// System
+use embassy_embedded_hal::shared_bus::blocking::i2c::I2cDevice;
+use embassy_time::Timer;
+use rtt_target::rprintln;
+
+// Sensor
+use scd4x::Scd4x;
+
+use crate::I2c0BusType;
+
+#[embassy_executor::task]
+pub async fn sensor_read_task(i2c_bus: &'static I2c0BusType) {
+    rprintln!("Sensor read task started");
+
+    Timer::after_millis(30).await; // SCD41 power-up delay
+    let i2c_dev = I2cDevice::new(i2c_bus);
+
+    let mut scd41 = Scd4x::new(i2c_dev, embassy_time::Delay);
+    scd41.wake_up();
+    scd41.reinit().unwrap();
+
+    match scd41.serial_number() {
+        Ok(serial) => rprintln!("[SCD41] Serial number: {}", serial),
+        Err(error) => rprintln!(
+            "[SCD41] Error: did not respond to get_serial_number: {:?}",
+            error
+        ),
+    }
+
+    scd41.start_periodic_measurement().unwrap();
+
+    loop {
+        Timer::after_secs(5).await; // start_periodic_measurement() returns new sensor data every 5 seconds
+
+        match scd41.measurement() {
+            Ok(data) => {
+                rprintln!(
+                    "[SCD41] CO2: {} ppm, temperature: {} C, humidity: {} RH",
+                    data.co2,
+                    data.temperature,
+                    data.humidity
+                );
+            }
+            Err(error) => {
+                rprintln!(
+                    "[SCD41] Error: failed to retrieve measurement data: {:?}",
+                    error
+                );
+                break;
+            }
+        }
+    }
+}