Manually sending an I2C stop command.

It says after the current byte, not the next byte. If you're not currently sending anything (and clock is stretched), it should be immediate. Are you seeing something different?

Can't send a stop command mid-byte.

For reference, this is what I have. It works if I immediatly stop the transfer, otherwise it will eventually stop sending data.  I assume this could be becuase of some kind of bus error which I'm not checking for yet.  And yeah, it does appear to behave differently, in terms of the stop flag, than my example above.  The problem with this code, in addition to it eventually crashing, is that it requires that I send some data to get a stop byte.

 my_transfer (dac.hi2c, dac._i2cAddress, NULL, 0, 1000);
 my_transfer (dac.hi2c, dac._i2cAddress, buffer, 2, 1000);
 my_transfer (dac.hi2c, dac._i2cAddress, buffer, -2, 1000);

#define MAX_NBYTE_SIZE 255
int my_transfer (I2C_HandleTypeDef *hi2c, uint16_t DevAddress, uint8_t *pData,
 int16_t Size, uint32_t Timeout)
{

 uint32_t tickstart = HAL_GetTick ();

 if (hi2c->State != HAL_I2C_STATE_READY)
 {
 //return HAL_ERROR;
 }

 /* Process Locked */
 //__HAL_LOCK(hi2c);
 hi2c->State = HAL_I2C_STATE_BUSY_TX;
 hi2c->Mode = HAL_I2C_MODE_MASTER;
 hi2c->ErrorCode = HAL_I2C_ERROR_NONE;
 hi2c->pBuffPtr = pData;
 hi2c->XferCount = abs (Size);
 hi2c->XferISR = NULL;

 // normally you check if the transfer is larger than 255, we're going to skip that for now and assume <255
 if (hi2c->XferCount > MAX_NBYTE_SIZE)
 return 1;

 if (Size == 0)
 {
 /* Send Slave Address */
 I2C_TransferConfig (hi2c, DevAddress,
 (uint8_t) MAX_NBYTE_SIZE,
 I2C_SOFTEND_MODE, //I2C_SOFTEND_MODE,	// DONT send a stop
 I2C_GENERATE_START_WRITE);

 }
 else if (Size < 0)
 {
 I2C_TransferConfig (hi2c, DevAddress, hi2c->XferCount,
 I2C_SOFTEND_MODE,
 I2C_NO_STARTSTOP);

 while (hi2c->XferCount > 0U)
 {
 /* Write data to TXDR */
 hi2c->Instance->TXDR = *hi2c->pBuffPtr;

 /* Increment Buffer pointer */
 hi2c->pBuffPtr++;

 hi2c->XferCount--;

 /* Wait until TXIS flag is set */
 if (I2C_WaitOnTXISFlagUntilTimeout (hi2c, Timeout, tickstart) != HAL_OK)
 {
 return HAL_ERROR;
 }
 }

 hi2c->Instance->CR2 |= I2C_CR2_STOP;

 if (I2C_WaitOnSTOPFlagUntilTimeout (hi2c, Timeout, tickstart) != HAL_OK)
 {
 return HAL_ERROR;
 }

 /* Clear STOP Flag */
 __HAL_I2C_CLEAR_FLAG(hi2c, I2C_FLAG_STOPF);

 /* Clear Configuration Register 2 */
 I2C_RESET_CR2(hi2c);

 hi2c->State = HAL_I2C_STATE_READY;
 hi2c->Mode = HAL_I2C_MODE_NONE;
 }
 else if (Size != 0)
 {
 I2C_TransferConfig (hi2c, DevAddress, hi2c->XferCount,
 I2C_SOFTEND_MODE,
 I2C_NO_STARTSTOP);

 while (hi2c->XferCount > 0U)
 {
 /* Write data to TXDR */
 hi2c->Instance->TXDR = *hi2c->pBuffPtr;

 /* Increment Buffer pointer */
 hi2c->pBuffPtr++;

 hi2c->XferCount--;

 /* Wait until TXIS flag is set */
 if (I2C_WaitOnTXISFlagUntilTimeout (hi2c, Timeout, tickstart) != HAL_OK)
 {
 return HAL_ERROR;
 }

 }
 return HAL_OK;
 }

 /* Process Unlocked */
 // __HAL_UNLOCK(hi2c);
 return HAL_OK;
}

Just went back to look at my code. Setting STOP immediately sends a stop condition for me. No need to send a new byte.

I2C_TransferConfig isn't meant to be called directly and does a lot of other things other than just setting STOP.

If the interrupt keeps happening, look at the flags and determine why. This should be straightforward.