I have an STM32WB design using I2C to get 6 bytes from a BMI0888 every 50ms (triggered by an external interrupt). The interrupt sets a flag in my main loop to go get the data. The devices first requires you to write the desired register, then read the 6 bytes. If I use back to back calls to HAL_I2C_Master_Transmit followed by HAL_I2C_Master_Receive, it works great. See figure 1 below. That will happen every 50ms.
I am now trying to do this using the interrupt versions of the functions. If I try and use HAL_I2C_Master_Transmit_IT and HAL_I2C_Master_Transmit_IT. I again use flags to inform my main loop what to do. The external interrupt flags the loop to perform the transmit, then the HAL_I2C_MasterTxCpltCallback informs the main loop to perform the receive, and then HAL_I2C_MasterRxCpltCallback tells the main loop the data is ready. I get all of these interrupts, however the data isn't actually read. See figure 2 below where SCL stops high.
Blocking:
Interrupt:
I traced the execution of this and found where it's failing, but I don't know why.
First I transfer a register I want to read. I'm intentionally doing this as multiple steps rather than use the MemRead functions:
status = HAL_I2C_Master_Transmit_IT (
&hi2c1, ACC_ADDR,
®Addr, 1);
After I get the complete-interrupt from that, and observe it on a scope, I then two a 6-byte read. I follow it with a while(1) so that I know nothing else will happen with the i2c line.
status = HAL_I2C_Master_Receive_IT(
&hi2c1,
ACC_ADDR,
buffer,
6);
while(1)
{ }
That function calls
I2C_TransferConfig(hi2c, DevAddress, (uint8_t)hi2c->XferSize, xfermode, I2C_GENERATE_START_READ);
When this is called the device will transfer the slave address and then receive the first 2-bytes but NOT the last ack. At which point the clock goes low. It stays low forever.
The I2C_Master_ISR_IT interrupt is triggered which does this:
/* Remove RXNE flag on temporary variable as read done */
tmpITFlags &= ~I2C_FLAG_RXNE;
/* Read data from RXDR */
*hi2c->pBuffPtr = (uint8_t)hi2c->Instance->RXDR;
/* Increment Buffer pointer */
hi2c->pBuffPtr++;
hi2c->XferSize--;
hi2c->XferCount--;
This interrupt will fire 6 times, each time running the code above, but scl stays low. On the 6-th call the I2C_ITMasterCplt function is called because it thinks the transfer is done.
At this point the registers are. I don't see any errors here, and I see a stopf. Again, scl is still low and the last 4 bytes are never actually clocked:
The manual describes this exact behavior is RXDR isn't read. Specifically that SCL will stretch between and 8th and 9th bit. However I am seeing the callback in the hal read from RXDR yet nothing happens on the line:
