preliminary UART setup for CO2 sensor

firmware/Cargo.lock

@@ -637,6 +637,7 @@ dependencies = [
  "esp-idf-svc",
  "esp-idf-sys",
  "log",
+ "mh-z19",
 ]
 
 [[package]]
@@ -946,6 +947,12 @@ version = "2.7.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "32a282da65faaf38286cf3be983213fcf1d2e2a58700e808f83f4ea9a4804bc0"
 
+[[package]]
+name = "mh-z19"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "08e20228a4dda61bd521e7316780ba2ec8d88170e4999fbd641c1da98e2eea28"
+
 [[package]]
 name = "minimal-lexical"
 version = "0.2.1"

firmware/Cargo.toml

@@ -28,6 +28,7 @@ esp-idf-svc = "0.51"
 bme280 = "0.5.1"
 esp-idf-hal = "0.45.2" 
 esp-idf-sys = { version = "0.36.1", features = ["binstart"] }
+mh-z19 = "0.3.3"
 
 # --- Optional Embassy Integration ---
 # esp-idf-svc = { version = "0.51", features = ["critical-section", "embassy-time-driver", "embassy-sync"] }

firmware/src/main.rs

@@ -6,8 +6,11 @@ use esp_idf_hal::{
         ADC2,
     },
     delay::Delay,
+    gpio,
     i2c::{I2cConfig, I2cDriver, I2cError},
     prelude::Peripherals,
+    uart::{config, UartDriver},
+    units::Hertz,
 };
 
 struct InitResult<'s, I2C> {
@@ -113,6 +116,27 @@ fn init<'a>() -> InitResult<'a, I2cDriver<'a>> {
 
     log::info!("ADC2  channel driver@GPIO4 initialized!");
 
+    //set up mh-Z19B CO2 sensor
+    let tx_pin = peripherals.pins.gpio5;
+    let rx_pin = peripherals.pins.gpio6;
+
+    //obtain UART connection
+    let uart_config = config::Config::new().baudrate(Hertz(115_200));
+    let uart = match UartDriver::new(
+        peripherals.uart1,
+        tx_pin,
+        rx_pin,
+        Option::<gpio::AnyIOPin>::None,
+        Option::<gpio::AnyIOPin>::None,
+        &uart_config,
+    ) {
+        Ok(uart_drv) => uart_drv,
+        Err(error) => {
+            log::error!("Error initializing UART connection: {error}.");
+            panic!();
+        }
+    };
+
     InitResult {
         bme280: bme280,
         no2_adc: adc_channel_driver,