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Fix I2C slave issue #216

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Merged
merged 2 commits into from
Feb 2, 2018
Merged

Fix I2C slave issue #216

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86e0bbc
Fix I2C slave issue: Rx buffer allocation
fpistm Feb 2, 2018
b1b12de
Fix I2C slave issue: return correct size
fpistm Feb 2, 2018
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2 changes: 1 addition & 1 deletion cores/arduino/stm32/twi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
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Aren't you using HAL_I2C_SlaveRxCpltCallback and HAL_I2C_SlaveTxCpltCallback ?

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no, only HAL_I2C_ListenCpltCallback

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Ok. then it's not easy for me to understand the code. If this works - fine. But I think ListenCpltCallback does not mean that data has been transmitted already, so I don't understand the lines above and why XferCount is replaced by XferSize

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@fpistm fpistm Feb 2, 2018 •
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Right, I think, that we missed that when @fprwi6labs do the #135.
While I2C is sequential it seems to be OK but this will need to be review to handle that properly.
Anyway this PR fix buffer allocation, so I will merge it and raise new issue to track the code review with HAL_I2C_SlaveRxCpltCallback and HAL_I2C_SlaveTxCpltCallback

if(nbData != 0) {
obj->i2c_onSlaveReceive(obj->i2cTxRxBuffer, nbData);
}
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9 changes: 8 additions & 1 deletion libraries/Wire/src/Wire.cpp
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Expand Up @@ -380,6 +380,13 @@ void TwoWire::onReceiveService(uint8_t* inBytes, int numBytes)
if(rxBufferIndex < rxBufferLength){
return;
}

allocateRxBuffer(numBytes);
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Wouldn't it be better to do as little as possible inside the ISR? - I.e do the RX buffer allocation in begin() when slave mode is detected.

Since the current implementation of onReceiveService() never appends data to the RX buffer (it always start writing at index 0) it should be safe to allocate the buffer in begin().
At least as long as I2C_TXRX_BUFFER_SIZE <= BUFFER_LENGTH (add a static_assert for safety)

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if numbytes is greater than the one allocated it need realloc

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yes, but it will never be greater. I2C_TXRX_BUFFER_SIZE = BUFFER_LENGTH = 32 (at least for now)

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allocateRxBuffer(numBytes) can still be called in the ISR, just to make sure.
In the normal case it will do nothing if the buffer is pre-allocated in begin()

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you're right in case of slave receive. I will check all those things when I will review #217

// 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);
Expand Down Expand Up @@ -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.
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2 changes: 1 addition & 1 deletion libraries/Wire/src/Wire.h
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Expand Up @@ -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);
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