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Fix STM32 I2C v2 async transfer not doing a repeated start #197

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Nov 22, 2023
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Fix STM32 I2C v2 async transfer not doing a repeated start #197

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54bcbda
Fix STM32 I2C v2 async transfer not doing a repeated start
multiplemonomials Nov 21, 2023
4866b8d
Clarify docs
multiplemonomials Nov 21, 2023
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10 changes: 6 additions & 4 deletions drivers/include/drivers/I2C.h
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Original file line number Diff line number Diff line change
Expand Up @@ -377,7 +377,8 @@ class I2C : private NonCopyable<I2C> {
*
* The %I2C peripheral will begin a transmit and/or receive operation in the background. If only a transmit
* or receive buffer is specified, only a transmit or receive will be done. If both buffers are specified,
* first the transmission is done to the given slave address, then the specified number of bytes are received.
* first the transmission is done to the given slave address, then the MCU performs a repeated start
* and the specified number of bytes are received.
*
* If you wish to find out when the transfer is done, pass a callback function to the callback argument
* and set the event argument to the events you wish to receive.
Expand All @@ -400,7 +401,7 @@ class I2C : private NonCopyable<I2C> {
* of the flags I2C_EVENT_ERROR, I2C_EVENT_ERROR_NO_SLAVE, I2C_EVENT_TRANSFER_COMPLETE, or I2C_EVENT_TRANSFER_EARLY_NACK
* @param callback The event callback function
* @param repeated Set up for a repeated start. If true, the Mbed processor does not relinquish the bus after
* this write operation. You may then call write(), read(), or start() again to start another operation.
* this operation. You may then call write(), read(), start(), or transfer() again to start another operation.
*
* @returns Zero if the transfer has started, or -1 if I2C peripheral is busy
*/
Expand All @@ -415,7 +416,8 @@ class I2C : private NonCopyable<I2C> {
*
* The %I2C peripheral will begin a transmit and/or receive operation in the background. If only a transmit
* or receive buffer is specified, only a transmit or receive will be done. If both buffers are specified,
* first the transmission is done to the given slave address, then the specified number of bytes are received.
* first the transmission is done to the given slave address, then the MCU performs a repeated start
* and the specified number of bytes are received.
*
* Internally, the chip vendor may implement this function using either DMA or interrupts.
*
Expand All @@ -428,7 +430,7 @@ class I2C : private NonCopyable<I2C> {
* @param rx_length The length of RX buffer in bytes If 0, no reception is done.
* @param timeout timeout value. Use #rtos::Kernel::wait_for_u32_forever to wait forever (the default).
* @param repeated Set up for a repeated start. If true, the Mbed processor does not relinquish the bus after
* this operation. You may then call write(), read(), or start() again to start another operation.
* this operation. You may then call write(), read(), start(), or transfer() again to start another operation.
*
* @returns Result code describing whether the transfer succeeded or not.
*/
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8 changes: 6 additions & 2 deletions targets/TARGET_STM/i2c_api.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1389,7 +1389,7 @@ void HAL_I2C_MasterTxCpltCallback(I2C_HandleTypeDef *hi2c)
if(obj->rx_buff.length > 0)
{
// This is a write-then-read transaction, switch to reading.
uint32_t xferOptions = obj_s->stop ? I2C_FIRST_AND_LAST_FRAME : I2C_FIRST_FRAME;
uint32_t xferOptions = get_hal_xfer_options(obj_s, obj_s->stop);
HAL_I2C_Master_Seq_Receive_IT(hi2c, obj_s->address, (uint8_t *) obj->rx_buff.buffer, obj->rx_buff.length,
xferOptions);
obj_s->state = STM_I2C_ASYNC_READ_IN_PROGRESS;
Expand Down Expand Up @@ -1784,7 +1784,11 @@ void i2c_transfer_asynch(i2c_t *obj, const void *tx, size_t tx_length, void *rx,

prep_for_restart_if_needed(obj_s);

uint32_t xferOptions = get_hal_xfer_options(obj_s, stop);
// If we are doing both a tx and an rx, then we never want to send a stop on the
// first transfer.
bool sendStopOnFirstTransfer = stop && ((tx_length == 0) || (rx_length == 0));

uint32_t xferOptions = get_hal_xfer_options(obj_s, sendStopOnFirstTransfer);

if(!i2c_is_ready_for_transaction_start(obj_s->state))
{
Expand Down