Read temperature from thermocouple

Cargo.lock

@@ -408,6 +408,7 @@ dependencies = [
  "embedded-graphics",
  "embedded-hal",
  "fugit",
+ "nb 1.1.0",
  "panic-halt",
  "rp-pico",
  "ssd1306",

Cargo.toml

@@ -12,6 +12,7 @@ display-interface = "0.4.1"
 embedded-graphics = "0.8.0"
 embedded-hal = "0.2.7"
 fugit = "0.3.7"
+nb = "1.1.0"
 panic-halt = "0.2.0"
 rp-pico = "0.7.0"
 ssd1306 = "0.8.0"

src/main.rs

@@ -1,21 +1,27 @@
 #![no_std]
 #![no_main]
 
+mod max6675;
+
+use core::str;
+
 use cortex_m::delay::Delay;
 
 use display_interface::DisplayError;
 
 use embedded_graphics::{
-    mono_font::{ascii::FONT_6X10, MonoTextStyleBuilder},
+    mono_font::{iso_8859_1::FONT_6X10, MonoTextStyle},
     pixelcolor::BinaryColor,
     prelude::*,
-    text::{Baseline, Text},
+    text::{Alignment, Text},
 };
 
 use embedded_hal::digital::v2::{InputPin, ToggleableOutputPin};
 
 use fugit::RateExtU32;
 
+use max6675::{Error, Max6675};
+
 use panic_halt as _;
 
 use rp_pico::{
@@ -25,13 +31,13 @@ use rp_pico::{
         gpio::PinState,
         i2c::I2C,
         usb::UsbBus,
-        Sio, Watchdog,
+        Sio, Timer, Watchdog,
     },
     pac::{CorePeripherals, Peripherals},
     Pins,
 };
 
-use ssd1306::{prelude::*, I2CDisplayInterface, Ssd1306};
+use ssd1306::{mode::BufferedGraphicsMode, prelude::*, I2CDisplayInterface, Ssd1306};
 
 use usb_device::{bus::UsbBus as UsbBusTrait, bus::UsbBusAllocator, prelude::*};
 
@@ -58,6 +64,14 @@ fn print_serial<'a, B: UsbBusTrait>(
     Ok(())
 }
 
+fn println_serial<'a, B: UsbBusTrait>(
+    serial: &mut SerialPort<'a, B>,
+    msg: &str,
+) -> Result<(), UsbError> {
+    print_serial(serial, msg)?;
+    print_serial(serial, "\r\n")
+}
+
 fn stringify_display_error(err: DisplayError) -> &'static str {
     match err {
         DisplayError::InvalidFormatError => "invalid format",
@@ -71,6 +85,27 @@ fn stringify_display_error(err: DisplayError) -> &'static str {
     }
 }
 
+fn display_text<DI, SIZE>(
+    display: &mut Ssd1306<DI, SIZE, BufferedGraphicsMode<SIZE>>,
+    text: &str,
+) -> Result<(), DisplayError>
+where
+    DI: WriteOnlyDataCommand,
+    SIZE: DisplaySize,
+{
+    let (w, h) = display.dimensions();
+
+    Text::with_alignment(
+        text,
+        Point::new((w / 2).into(), (h / 2).into()),
+        MonoTextStyle::new(&FONT_6X10, BinaryColor::On),
+        Alignment::Center,
+    )
+    .draw(display)?;
+
+    display.flush()
+}
+
 #[entry]
 fn main() -> ! {
     let mut p = Peripherals::take().unwrap();
@@ -110,7 +145,7 @@ fn main() -> ! {
         .device_class(USB_CLASS_CDC)
         .build();
 
-    for _ in 0..2000 {
+    for _ in 0..1000 {
         delay.delay_ms(5);
 
         if !usb_dev.poll(&mut [&mut serial]) {
@@ -124,7 +159,7 @@ fn main() -> ! {
         }
     }
 
-    let _ = print_serial(&mut serial, "Hello, world!\r\n");
+    let _ = println_serial(&mut serial, "Hello, world!");
 
     let i2c = I2C::i2c0(
         p.I2C0,
@@ -148,26 +183,15 @@ fn main() -> ! {
         panic!();
     }
 
-    let text_style = MonoTextStyleBuilder::new()
+    let so = pins.gpio6.into_floating_input();
-        .font(&FONT_6X10)
+    let cs = pins.gpio7.into_push_pull_output_in_state(PinState::High);
-        .text_color(BinaryColor::On)
+    let sck = pins.gpio8.into_push_pull_output();
-        .build();
 
-    let result = Text::with_baseline("Hello, world!", Point::zero(), text_style, Baseline::Top)
+    let mut thermocouple = Max6675::new(cs, sck, so);
-        .draw(&mut display)
+    let timer = Timer::new(p.TIMER, &mut p.RESETS);
-        .map_err(stringify_display_error);
-    if let Err(msg) = result {
-        let _ = print_serial(&mut serial, msg);
-        panic!();
-    }
-
-    let result = display.flush().map_err(stringify_display_error);
-    if let Err(msg) = result {
-        let _ = print_serial(&mut serial, msg);
-    }
 
     let mut relay = pins.gpio14.into_push_pull_output_in_state(PinState::Low);
-    let tmp_button = pins.gpio15.into_pull_up_input();
+    let button = pins.gpio15.into_pull_up_input();
 
     let mut led = pins.led.into_push_pull_output_in_state(PinState::Low);
 
@@ -179,10 +203,36 @@ fn main() -> ! {
         if counter == 0 {
             led.toggle().unwrap();
 
-            let _ = print_serial(&mut serial, "ping\r\n");
+            let mut bytes: [u8; 8] = [32, 32, 32, 32, 32, 194, 176, 67];
+            let text = match thermocouple.read_temperature(&mut timer.count_down()) {
+                Ok(mut temperature) => {
+                    temperature >>= 2;
+
+                    for i in (0..4).rev() {
+                        bytes[i] = 48u8 + (temperature % 10) as u8;
+                        temperature /= 10;
+
+                        if temperature == 0 {
+                            break;
+                        }
                     }
 
-        if tmp_button.is_low().unwrap() {
+                    str::from_utf8(&bytes).unwrap()
+                }
+                Err(Error::IOError) => "i/o error",
+                Err(Error::OpenThermocouple) => "n/c",
+            };
+
+            let _ = println_serial(&mut serial, text);
+
+            display.clear_buffer();
+
+            if let Err(err) = display_text(&mut display, text) {
+                let _ = println_serial(&mut serial, stringify_display_error(err));
+            }
+        }
+
+        if button.is_low().unwrap() {
             relay.toggle().unwrap();
             delay.delay_ms(1000);
         }

src/max6675.rs

@@ -0,0 +1,76 @@
+use embedded_hal::{
+    digital::v2::{InputPin, OutputPin},
+    timer::CountDown,
+};
+
+use fugit::{ExtU64, MicrosDurationU64};
+
+use nb::block;
+
+#[derive(Debug)]
+pub enum Error {
+    IOError,
+    OpenThermocouple,
+}
+
+pub struct Max6675<CS, SCK, SO>
+where
+    CS: OutputPin,
+    SCK: OutputPin,
+    SO: InputPin,
+{
+    cs: CS,
+    sck: SCK,
+    so: SO,
+}
+
+impl<CS, SCK, SO> Max6675<CS, SCK, SO>
+where
+    CS: OutputPin,
+    SCK: OutputPin,
+    SO: InputPin,
+{
+    pub fn new(cs: CS, sck: SCK, so: SO) -> Self {
+        Self { cs, sck, so }
+    }
+
+    pub fn read_temperature<CD>(&mut self, timer: &mut CD) -> Result<u16, Error>
+    where
+        CD: CountDown,
+        CD::Time: From<MicrosDurationU64>,
+    {
+        self.cs.set_low().map_err(|_| Error::IOError)?;
+        delay(timer, 10.micros());
+
+        let mut d = 0u16;
+
+        for i in (0..16).rev() {
+            self.sck.set_low().map_err(|_| Error::IOError)?;
+            delay(timer, 10.micros());
+
+            if self.so.is_high().map_err(|_| Error::IOError)? {
+                d |= 1 << i;
+            }
+
+            self.sck.set_high().map_err(|_| Error::IOError)?;
+            delay(timer, 10.micros());
+        }
+
+        self.cs.set_high().map_err(|_| Error::IOError)?;
+
+        if d & 0x4 == 0x4 {
+            Err(Error::OpenThermocouple)
+        } else {
+            Ok(d >> 3)
+        }
+    }
+}
+
+fn delay<CD>(timer: &mut CD, t: MicrosDurationU64)
+where
+    CD: CountDown,
+    CD::Time: From<MicrosDurationU64>,
+{
+    timer.start(t);
+    block!(timer.wait()).unwrap();
+}