Add preliminary I2C implementation for RP2040

4 files changed, 231 insertions, 1 deletions

diff --git a/embassy-rp/src/clocks.rs b/embassy-rp/src/clocks.rs
index 1c446f38..875c129c 100644
--- a/embassy-rp/src/clocks.rs
+++ b/embassy-rp/src/clocks.rs
@@ -114,7 +114,7 @@ pub unsafe fn init() {
     reset::unreset_wait(peris);
 }
 
-pub(crate) fn _clk_sys_freq() -> u32 {
+pub(crate) fn clk_sys_freq() -> u32 {
     125_000_000
 }
 
diff --git a/embassy-rp/src/i2c.rs b/embassy-rp/src/i2c.rs
new file mode 100644
index 00000000..4a27ee8d
--- /dev/null
+++ b/embassy-rp/src/i2c.rs
@@ -0,0 +1,221 @@
+use core::marker::PhantomData;
+
+use embassy_hal_common::into_ref;
+use pac::i2c;
+
+use crate::{pac, peripherals, Peripheral};
+
+/// I2C error
+#[derive(Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub enum Error {
+    /// I2C abort with error
+    Abort(u32),
+    /// User passed in a read buffer that was 0 length
+    InvalidReadBufferLength,
+    /// User passed in a write buffer that was 0 length
+    InvalidWriteBufferLength,
+    /// Target i2c address is out of range
+    AddressOutOfRange(u16),
+    /// Target i2c address is reserved
+    AddressReserved(u16),
+}
+
+#[non_exhaustive]
+#[derive(Copy, Clone)]
+pub struct Config {
+    pub frequency: u32,
+    pub sda_pullup: bool,
+    pub scl_pullup: bool,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Self {
+            frequency: 100_000,
+            sda_pullup: false,
+            scl_pullup: false,
+        }
+    }
+}
+
+pub struct I2c<'d, T: Instance, M: Mode> {
+    phantom: PhantomData<(&'d mut T, M)>,
+}
+
+impl<'d, T: Instance> I2c<'d, T, Master> {
+    pub fn new_master(
+        _peri: impl Peripheral<P = T> + 'd,
+        scl: impl Peripheral<P = impl SclPin<T>> + 'd,
+        sda: impl Peripheral<P = impl SdaPin<T>> + 'd,
+        config: Config,
+    ) -> Self {
+        into_ref!(_peri, scl, sda);
+
+        assert!(config.frequency <= 1_000_000);
+        assert!(config.frequency > 0);
+
+        let p = T::regs();
+
+        unsafe {
+            p.ic_enable().write(|w| w.set_enable(false));
+
+            // select controller mode & speed
+            p.ic_con().write(|w| {
+                // Always use "fast" mode (<= 400 kHz, works fine for standard mode too)
+                w.set_speed(i2c::vals::Speed::FAST);
+                w.set_master_mode(true);
+                w.set_ic_slave_disable(true);
+                w.set_ic_restart_en(true);
+                w.set_tx_empty_ctrl(true);
+            });
+
+            // Clear FIFO threshold
+            p.ic_tx_tl().write(|w| w.set_tx_tl(0));
+            p.ic_rx_tl().write(|w| w.set_rx_tl(0));
+
+            // Configure SCL & SDA pins
+            scl.io().ctrl().write(|w| w.set_funcsel(3));
+            sda.io().ctrl().write(|w| w.set_funcsel(3));
+
+            scl.pad_ctrl().write(|w| {
+                w.set_schmitt(true);
+                w.set_pue(config.scl_pullup);
+            });
+            sda.pad_ctrl().write(|w| {
+                w.set_schmitt(true);
+                w.set_pue(config.sda_pullup);
+            });
+
+            // Configure baudrate
+
+            // There are some subtleties to I2C timing which we are completely ignoring here
+            // See: https://github.com/raspberrypi/pico-sdk/blob/bfcbefafc5d2a210551a4d9d80b4303d4ae0adf7/src/rp2_common/hardware_i2c/i2c.c#L69
+            let clk_base = crate::clocks::clk_sys_freq();
+
+            let period = (clk_base + config.frequency / 2) / config.frequency;
+            let lcnt = period * 3 / 5; // spend 3/5 (60%) of the period low
+            let hcnt = period - lcnt; // and 2/5 (40%) of the period high
+
+            // Check for out-of-range divisors:
+            assert!(hcnt <= 0xffff);
+            assert!(lcnt <= 0xffff);
+            assert!(hcnt >= 8);
+            assert!(lcnt >= 8);
+
+            // Per I2C-bus specification a device in standard or fast mode must
+            // internally provide a hold time of at least 300ns for the SDA signal to
+            // bridge the undefined region of the falling edge of SCL. A smaller hold
+            // time of 120ns is used for fast mode plus.
+            let sda_tx_hold_count = if config.frequency < 1_000_000 {
+                // sda_tx_hold_count = clk_base [cycles/s] * 300ns * (1s / 1e9ns)
+                // Reduce 300/1e9 to 3/1e7 to avoid numbers that don't fit in uint.
+                // Add 1 to avoid division truncation.
+                ((clk_base * 3) / 10_000_000) + 1
+            } else {
+                // fast mode plus requires a clk_base > 32MHz
+                assert!(clk_base >= 32_000_000);
+
+                // sda_tx_hold_count = clk_base [cycles/s] * 120ns * (1s / 1e9ns)
+                // Reduce 120/1e9 to 3/25e6 to avoid numbers that don't fit in uint.
+                // Add 1 to avoid division truncation.
+                ((clk_base * 3) / 25_000_000) + 1
+            };
+            assert!(sda_tx_hold_count <= lcnt - 2);
+
+            p.ic_fs_scl_hcnt().write(|w| w.set_ic_fs_scl_hcnt(hcnt as u16));
+            p.ic_fs_scl_lcnt().write(|w| w.set_ic_fs_scl_lcnt(lcnt as u16));
+            p.ic_fs_spklen()
+                .write(|w| w.set_ic_fs_spklen(if lcnt < 16 { 1 } else { (lcnt / 16) as u8 }));
+            p.ic_sda_hold()
+                .write(|w| w.set_ic_sda_tx_hold(sda_tx_hold_count as u16));
+
+            // Enable I2C block
+            p.ic_enable().write(|w| w.set_enable(true));
+        }
+
+        Self { phantom: PhantomData }
+    }
+}
+
+mod sealed {
+    pub trait Instance {}
+    pub trait Mode {}
+
+    pub trait SdaPin<T: Instance> {}
+    pub trait SclPin<T: Instance> {}
+}
+
+pub trait Mode: sealed::Mode {}
+
+macro_rules! impl_mode {
+    ($name:ident) => {
+        impl sealed::Mode for $name {}
+        impl Mode for $name {}
+    };
+}
+
+pub struct Master;
+pub struct Slave;
+
+impl_mode!(Master);
+impl_mode!(Slave);
+
+pub trait Instance: sealed::Instance {
+    fn regs() -> pac::i2c::I2c;
+}
+
+macro_rules! impl_instance {
+    ($type:ident, $irq:ident) => {
+        impl sealed::Instance for peripherals::$type {}
+        impl Instance for peripherals::$type {
+            fn regs() -> pac::i2c::I2c {
+                pac::$type
+            }
+        }
+    };
+}
+
+impl_instance!(I2C0, I2c0);
+impl_instance!(I2C1, I2c1);
+
+pub trait SdaPin<T: Instance>: sealed::SdaPin<T> + crate::gpio::Pin {}
+pub trait SclPin<T: Instance>: sealed::SclPin<T> + crate::gpio::Pin {}
+
+macro_rules! impl_pin {
+    ($pin:ident, $instance:ident, $function:ident) => {
+        impl sealed::$function<peripherals::$instance> for peripherals::$pin {}
+        impl $function<peripherals::$instance> for peripherals::$pin {}
+    };
+}
+
+impl_pin!(PIN_0, I2C0, SdaPin);
+impl_pin!(PIN_1, I2C0, SclPin);
+impl_pin!(PIN_2, I2C1, SdaPin);
+impl_pin!(PIN_3, I2C1, SclPin);
+impl_pin!(PIN_4, I2C0, SdaPin);
+impl_pin!(PIN_5, I2C0, SclPin);
+impl_pin!(PIN_6, I2C1, SdaPin);
+impl_pin!(PIN_7, I2C1, SclPin);
+impl_pin!(PIN_8, I2C0, SdaPin);
+impl_pin!(PIN_9, I2C0, SclPin);
+impl_pin!(PIN_10, I2C1, SdaPin);
+impl_pin!(PIN_11, I2C1, SclPin);
+impl_pin!(PIN_12, I2C0, SdaPin);
+impl_pin!(PIN_13, I2C0, SclPin);
+impl_pin!(PIN_14, I2C1, SdaPin);
+impl_pin!(PIN_15, I2C1, SclPin);
+impl_pin!(PIN_16, I2C0, SdaPin);
+impl_pin!(PIN_17, I2C0, SclPin);
+impl_pin!(PIN_18, I2C1, SdaPin);
+impl_pin!(PIN_19, I2C1, SclPin);
+impl_pin!(PIN_20, I2C0, SdaPin);
+impl_pin!(PIN_21, I2C0, SclPin);
+impl_pin!(PIN_22, I2C1, SdaPin);
+impl_pin!(PIN_23, I2C1, SclPin);
+impl_pin!(PIN_24, I2C0, SdaPin);
+impl_pin!(PIN_25, I2C0, SclPin);
+impl_pin!(PIN_26, I2C1, SdaPin);
+impl_pin!(PIN_27, I2C1, SclPin);
+impl_pin!(PIN_28, I2C0, SdaPin);
+impl_pin!(PIN_29, I2C0, SclPin);
diff --git a/embassy-rp/src/lib.rs b/embassy-rp/src/lib.rs
index 9ac98d22..e784399d 100644
--- a/embassy-rp/src/lib.rs
+++ b/embassy-rp/src/lib.rs
@@ -8,6 +8,7 @@ mod intrinsics;
 
 pub mod dma;
 pub mod gpio;
+pub mod i2c;
 pub mod interrupt;
 pub mod rom_data;
 pub mod rtc;
@@ -75,6 +76,9 @@ embassy_hal_common::peripherals! {
     SPI0,
     SPI1,
 
+    I2C0,
+    I2C1,
+
     DMA_CH0,
     DMA_CH1,
     DMA_CH2,
diff --git a/embassy-rp/src/uart/mod.rs b/embassy-rp/src/uart/mod.rs
index d9285ee5..567c79db 100644
--- a/embassy-rp/src/uart/mod.rs
+++ b/embassy-rp/src/uart/mod.rs
@@ -428,9 +428,11 @@ mod eh02 {
 
     impl<'d, T: Instance, M: Mode> embedded_hal_02::blocking::serial::Write<u8> for UartTx<'d, T, M> {
         type Error = Error;
+
         fn bwrite_all(&mut self, buffer: &[u8]) -> Result<(), Self::Error> {
             self.blocking_write(buffer)
         }
+
         fn bflush(&mut self) -> Result<(), Self::Error> {
             self.blocking_flush()
         }
@@ -438,6 +440,7 @@ mod eh02 {
 
     impl<'d, T: Instance, M: Mode> embedded_hal_02::serial::Read<u8> for Uart<'d, T, M> {
         type Error = Error;
+
         fn read(&mut self) -> Result<u8, nb::Error<Self::Error>> {
             embedded_hal_02::serial::Read::read(&mut self.rx)
         }
@@ -445,9 +448,11 @@ mod eh02 {
 
     impl<'d, T: Instance, M: Mode> embedded_hal_02::blocking::serial::Write<u8> for Uart<'d, T, M> {
         type Error = Error;
+
         fn bwrite_all(&mut self, buffer: &[u8]) -> Result<(), Self::Error> {
             self.blocking_write(buffer)
         }
+
         fn bflush(&mut self) -> Result<(), Self::Error> {
             self.blocking_flush()
         }