SNS - I2C Mux (HYPE-13)

boards/stm32f767zi/src/io/i2c.rs

@@ -41,6 +41,23 @@ impl<'d> HypedI2c for Stm32f767ziI2c<'d> {
             }),
         }
     }
+
+    /// Write a byte to a device
+    fn write_byte(&mut self, device_address: u8, data: u8) -> Result<(), I2cError> {
+        let result = self.i2c.blocking_write(device_address, [data].as_ref());
+        match result {
+            Ok(_) => Ok(()),
+            Err(e) => Err(match e {
+                embassy_stm32::i2c::Error::Bus => I2cError::Bus,
+                embassy_stm32::i2c::Error::Arbitration => I2cError::Arbitration,
+                embassy_stm32::i2c::Error::Nack => I2cError::Nack,
+                embassy_stm32::i2c::Error::Timeout => I2cError::Timeout,
+                embassy_stm32::i2c::Error::Crc => I2cError::Crc,
+                embassy_stm32::i2c::Error::Overrun => I2cError::Overrun,
+                embassy_stm32::i2c::Error::ZeroLengthTransfer => I2cError::ZeroLengthTransfer,
+            }),
+        }
+    }
 }
 
 impl<'d> Stm32f767ziI2c<'d> {

boards/stm32l476rg/src/io/i2c.rs

@@ -41,6 +41,23 @@ impl<'d> HypedI2c for Stm32l476rgI2c<'d> {
             }),
         }
     }
+
+    /// Write a byte to a device
+    fn write_byte(&mut self, device_address: u8, data: u8) -> Result<(), I2cError> {
+        let result = self.i2c.blocking_write(device_address, [data].as_ref());
+        match result {
+            Ok(_) => Ok(()),
+            Err(e) => Err(match e {
+                embassy_stm32::i2c::Error::Bus => I2cError::Bus,
+                embassy_stm32::i2c::Error::Arbitration => I2cError::Arbitration,
+                embassy_stm32::i2c::Error::Nack => I2cError::Nack,
+                embassy_stm32::i2c::Error::Timeout => I2cError::Timeout,
+                embassy_stm32::i2c::Error::Crc => I2cError::Crc,
+                embassy_stm32::i2c::Error::Overrun => I2cError::Overrun,
+                embassy_stm32::i2c::Error::ZeroLengthTransfer => I2cError::ZeroLengthTransfer,
+            }),
+        }
+    }
 }
 
 impl<'d> Stm32l476rgI2c<'d> {

lib/core/Cargo.toml

@@ -10,7 +10,7 @@ rust-mqtt = { version = "0.3.0", default-features = false, features = ["defmt"]
 embedded-io-async = { version = "0.6.1" }
 rand_core = "0.6.3"
 serde = { version = "1.0", default-features = false, features = ["derive"] }
-embassy-net = { version = "0.4.0", default-features = false, features = ["defmt", "tcp", "proto-ipv4", "medium-ip"],  git = "https://github.com/embassy-rs/embassy", rev = "1c466b81e6af6b34b1f706318cc0870a459550b7"}
+embassy-net = { version = "0.4.0", default-features = false, features = ["defmt", "tcp", "proto-ipv4", "medium-ip"], git = "https://github.com/embassy-rs/embassy", rev = "1c466b81e6af6b34b1f706318cc0870a459550b7"}
 
 [features]
 std = []

lib/io/src/i2c.rs

@@ -21,4 +21,10 @@ pub trait HypedI2c {
         register_address: u8,
         data: u8,
     ) -> Result<(), I2cError>;
+    fn write_byte(&mut self, device_address: u8, data: u8) -> Result<(), I2cError>;
+}
+
+/// I2C mux trait used to abstract the I2C multiplexer
+pub trait HypedI2cMux: HypedI2c {
+    fn select_channel(&mut self) -> Result<(), I2cError>;
 }

lib/io/src/i2c_mux.rs

@@ -0,0 +1,68 @@
+use crate::i2c::{HypedI2c, HypedI2cMux, I2cError};
+
+pub struct I2cMux<T: HypedI2c> {
+    i2c: T,
+    mux_address: u8,
+    channel: u8,
+}
+
+pub enum I2cMuxError {
+    InvalidChannel,
+}
+
+impl<T: HypedI2c> I2cMux<T> {
+    pub fn new(i2c: T, channel: u8, mux_address: u8) -> Result<Self, I2cMuxError> {
+        // Check that the channel is valid
+        if channel >= MAX_MUX_CHANNELS {
+            return Err(I2cMuxError::InvalidChannel);
+        }
+        Ok(Self {
+            i2c,
+            channel,
+            mux_address,
+        })
+    }
+}
+
+impl<T: HypedI2c> HypedI2c for I2cMux<T> {
+    fn read_byte(&mut self, device_address: u8, register_address: u8) -> Option<u8> {
+        match self.select_channel() {
+            Ok(_) => self.i2c.read_byte(device_address, register_address),
+            Err(_) => None,
+        }
+    }
+
+    fn write_byte_to_register(
+        &mut self,
+        device_address: u8,
+        register_address: u8,
+        data: u8,
+    ) -> Result<(), I2cError> {
+        match self.select_channel() {
+            Ok(_) => self
+                .i2c
+                .write_byte_to_register(device_address, register_address, data),
+            Err(e) => Err(e as I2cError),
+        }
+    }
+
+    fn write_byte(&mut self, device_address: u8, data: u8) -> Result<(), I2cError> {
+        match self.select_channel() {
+            Ok(_) => self.i2c.write_byte(device_address, data),
+            Err(e) => Err(e as I2cError),
+        }
+    }
+}
+
+impl<T: HypedI2c> HypedI2cMux for I2cMux<T> {
+    /// Selects the channel on the multiplexer
+    fn select_channel(&mut self) -> Result<(), I2cError> {
+        match self.i2c.write_byte(self.mux_address, 1 << self.channel) {
+            Ok(_) => Ok(()),
+            Err(e) => Err(e as I2cError),
+        }
+    }
+}
+
+pub const DEFAULT_MUX_ADDRESS: u8 = 0x70;
+const MAX_MUX_CHANNELS: u8 = 8;

lib/io/src/lib.rs

@@ -2,4 +2,5 @@
 
 pub mod gpio;
 pub mod i2c;
+pub mod i2c_mux;
 pub mod spi;