Merge pull request stm32duino#216 from fpistm/slave_i2c

Fix I2C slave issue

Author: fpistm

cores/arduino/stm32/twi.c

@@ -539,7 +539,7 @@ void HAL_I2C_ListenCpltCallback(I2C_HandleTypeDef *hi2c)
 
   if((obj->i2c_onSlaveReceive != NULL) &&
     (obj->slaveMode == SLAVE_MODE_RECEIVE)) {
-    nbData = I2C_TXRX_BUFFER_SIZE - obj->handle.XferCount;
+    nbData = I2C_TXRX_BUFFER_SIZE - obj->handle.XferSize;
     if(nbData != 0) {
       obj->i2c_onSlaveReceive(obj->i2cTxRxBuffer, nbData);
     }

libraries/Wire/src/Wire.cpp

@@ -380,6 +380,13 @@ void TwoWire::onReceiveService(uint8_t* inBytes, int numBytes)
   if(rxBufferIndex < rxBufferLength){
     return;
   }
+
+  allocateRxBuffer(numBytes);
+  // error if no memory block available to allocate the buffer
+  if(rxBuffer == nullptr){
+    Error_Handler();
+  }
+
   // copy twi rx buffer into local read buffer
   // this enables new reads to happen in parallel
   memcpy(rxBuffer, inBytes, numBytes);
@@ -423,7 +430,7 @@ void TwoWire::onRequest( void (*function)(void) )
   * @note   Minimum allocated size is BUFFER_LENGTH)
   * @param  length: number of bytes to allocate
   */
-inline void TwoWire::allocateRxBuffer(size_t length)
+void TwoWire::allocateRxBuffer(size_t length)
 {
   if(rxBufferAllocated < length) {
   // By default we allocate BUFFER_LENGTH bytes. It is the min size of the buffer.

libraries/Wire/src/Wire.h

@@ -58,7 +58,7 @@ class TwoWire : public Stream
     static void onRequestService(void);
     static void onReceiveService(uint8_t*, int);
 
-    void allocateRxBuffer(size_t length);
+    static void allocateRxBuffer(size_t length);
     void allocateTxBuffer(size_t length);
 
     void resetRxBuffer(void);