Initial ADC impl (#52)

* Initial ADC + temp sensor support

rp2040-hal/src/adc.rs

@@ -1,3 +1,118 @@
 //! Analog-Digital Converter (ADC)
 // See [Chapter 4 Section 9](https://datasheets.raspberrypi.org/rp2040/rp2040_datasheet.pdf) for more details
 // TODO
+
+use hal::adc::{Channel, OneShot};
+use pac::{ADC, RESETS};
+
+use crate::{
+    gpio::Pin,
+    gpio::{
+        bank0::{Gpio26, Gpio27, Gpio28, Gpio29},
+        FloatingInput,
+    },
+    resets::SubsystemReset,
+};
+
+const TEMPERATURE_SENSOR_CHANNEL: u8 = 4;
+
+/// Adc
+pub struct Adc {
+    device: ADC,
+}
+
+impl Adc {
+    /// Create new adc struct and bring up adc
+    pub fn new(device: ADC, resets: &mut RESETS) -> Self {
+        device.reset_bring_down(resets);
+        device.reset_bring_up(resets);
+
+        // Enable adc
+        device.cs.write(|w| w.en().set_bit());
+
+        // Wait for adc ready
+        while !device.cs.read().ready().bit_is_set() {}
+
+        Self { device }
+    }
+
+    /// Free underlying register block
+    pub fn free(self) -> ADC {
+        self.device
+    }
+
+    /// Read single
+    pub fn read_single(&self) -> u16 {
+        self.device.result.read().result().bits()
+    }
+
+    /// Enable temperature sensor, returns a channel to use
+    pub fn enable_temp_sensor(&mut self) -> TempSense {
+        self.device.cs.modify(|_, w| w.ts_en().set_bit());
+
+        TempSense { __private: () }
+    }
+
+    /// Disable temperature sensor, consumes channel
+    pub fn disable_temp_sensor(&mut self, _: TempSense) {
+        self.device.cs.modify(|_, w| w.ts_en().clear_bit());
+    }
+}
+
+macro_rules! channel {
+    ($pin:ident, $channel:expr) => {
+        impl Channel<Adc> for Pin<$pin, FloatingInput> {
+            type ID = u8; // ADC channels are identified numerically
+
+            fn channel() -> u8 {
+                $channel
+            }
+        }
+    };
+}
+
+channel!(Gpio26, 0);
+channel!(Gpio27, 1);
+channel!(Gpio28, 2);
+channel!(Gpio29, 3);
+
+/// Internal temperature sensor type
+pub struct TempSense {
+    __private: (),
+}
+
+impl Channel<Adc> for TempSense {
+    type ID = u8; // ADC channels are identified numerically
+
+    fn channel() -> u8 {
+        TEMPERATURE_SENSOR_CHANNEL
+    }
+}
+
+impl<WORD, PIN> OneShot<Adc, WORD, PIN> for Adc
+where
+    WORD: From<u16>,
+    PIN: Channel<Adc, ID = u8>,
+{
+    type Error = ();
+
+    fn read(&mut self, _pin: &mut PIN) -> nb::Result<WORD, Self::Error> {
+        let chan = PIN::channel();
+
+        if chan == 4 {
+            self.device.cs.modify(|_, w| w.ts_en().set_bit())
+        }
+
+        if self.device.cs.read().ready().bit_is_set() {
+            self.device
+                .cs
+                .modify(|_, w| unsafe { w.ainsel().bits(chan).start_once().set_bit() });
+        };
+        if !self.device.cs.read().ready().bit_is_set() {
+            // Can't return WouldBlock here since that would take to long and next call conversion would be over
+            cortex_m::asm::nop();
+        };
+
+        Ok(self.device.result.read().result().bits().into())
+    }
+}