Fix i2c data lost on start repeat condition (#137)

Author: fayalalebrun

src/i2c/mod.rs

@@ -24,13 +24,23 @@ pub enum SlaveAddressMask {
     MaskAllBits,
 }
 
+/// Denotes which event marked the end of the I2C data
 #[derive(Debug, Clone, Copy)]
-pub enum I2cResult<'a> {
-    Data(u16, I2cDirection, &'a [u8]), // contains address, direction and data slice reference
-    Addressed(u16, I2cDirection),      // a slave is addressed by a master
+pub enum EndMarker {
+    /// A stop condition was encountered
+    Stop,
+    /// A start repeat condition was encountered
+    StartRepeat,
 }
 
 #[derive(Debug, Clone, Copy)]
+pub enum I2cResult<'a> {
+    /// Contains address, direction, data slice reference, and the packet delimeter
+    Data(u16, I2cDirection, &'a [u8], EndMarker),
+    Addressed(u16, I2cDirection), // a slave is addressed by a master
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
 pub enum I2cDirection {
     MasterReadSlaveWrite = 0,
     MasterWriteSlaveRead = 1,
@@ -99,4 +109,5 @@ pub struct I2c<I2C, SDA, SCL> {
     length_write_read: usize, // for a master write_read operation this remembers the size of the read operation
     // for a slave device this must be 0
     data: [u8; 255], // during transfer the driver will be the owner of the buffer
+    current_direction: I2cDirection,
 }

src/i2c/nonblocking.rs

@@ -2,7 +2,7 @@
 use crate::gpio::*;
 use crate::gpio::{AltFunction, OpenDrain, Output};
 use crate::i2c::config::Config;
-use crate::i2c::{Error, I2c, I2cDirection, I2cExt, I2cResult, SCLPin, SDAPin};
+use crate::i2c::{EndMarker, Error, I2c, I2cDirection, I2cExt, I2cResult, SCLPin, SDAPin};
 use crate::rcc::*;
 use crate::stm32::{I2C1, I2C2};
 use nb::Error::{Other, WouldBlock};
@@ -215,7 +215,8 @@ macro_rules! i2c {
                     length:0,
                     errors:0,
                     length_write_read:0,
-                    data:[0_u8;255]
+                    data:[0_u8;255],
+		    current_direction: I2cDirection::MasterReadSlaveWrite,
                 }
             }
             pub fn release(self) -> ($I2CX, SDA, SCL) {
@@ -306,7 +307,7 @@ macro_rules! i2c {
                     }
                     return Err( WouldBlock)
                 } else
-                if isr.rxne().bit_is_set() {
+                    if isr.rxne().bit_is_set() {
                     // read byte from the wire
                     if self.index < self.length {
                         self.data[self.index] = self.i2c.rxdr.read().rxdata().bits();
@@ -317,7 +318,8 @@ macro_rules! i2c {
                     }
                     return Err( WouldBlock)
                 } else
-                if isr.stopf().bit_is_set() {
+                    if isr.stopf().bit_is_set() {
+
                     // Clear the stop condition flag
                     self.i2c.icr.write(|w| w.stopcf().set_bit());
                     // Disable the watchdog
@@ -334,9 +336,13 @@ macro_rules! i2c {
                             }  else  {
                                 I2cDirection::MasterWriteSlaveRead
                             };
+			let index = self.index;
+			// Clear the length so we don't think there is still data when we reach the address phase
+			self.length = self.data.len();
+                        self.index = 0;
                         // return the actual amount of data (self.index), not the requested (self.length)
                         // application must evaluate the size of the frame
-                        return Ok( I2cResult::Data(self.address, direction,  &self.data[0..self.index]) )
+                        return Ok( I2cResult::Data(self.address, direction,  &self.data[0..index], EndMarker::Stop) )
                     }
                 }else
                 if isr.tc().bit_is_set() {
@@ -393,7 +399,14 @@ macro_rules! i2c {
 
                 } else
                 if isr.addr().bit_is_set() {
-                    // handle the slave device case, addressed by a master
+		    // Handle the case where there was no stop bit (repeated start)
+		    // In this case there will be data on the buffer which still needs to be delivered
+		    if self.current_direction == I2cDirection::MasterWriteSlaveRead && self.index >= 1 {
+			let index = self.index;
+			self.index = 0;
+			return Ok( I2cResult::Data(self.address, self.current_direction,  &self.data[0..index], EndMarker::StartRepeat) )
+		    }
+		    // handle the slave device case, addressed by a master
                     let current_address = isr.addcode().bits() as u16;
                     self.address = current_address;
                     // guard against misbehavior
@@ -419,7 +432,7 @@ macro_rules! i2c {
                             // return result
                             I2cDirection::MasterWriteSlaveRead
                         };
-
+		    self.current_direction = direction;
                     // do not yet release the clock stretching here
                     return Ok(I2cResult::Addressed(current_address, direction))
                 }