How to implement I2C communication between two STM32s.

[gocchan]

I'm implementing I2C communication using an STM32WBA2 as the Master and an STM32U0 as the Slave.
I've implemented a process to send one byte of data (0x75) from the Master to the Slave, with the Slave Address set to 0x68. However, when I check the SCL/SDA waveforms, it appears there's no ACK from the Slave.

On the other hand, the Slave receives an event in HAL_I2C_AddrCallback() when it receives 0x68, but the value read by HAL_I2C_Slave_Receive() is empty.
 

How can I receive 0x75 from the Master?
I've attached the main.c files for both the Master and Slave.
The CubeMX configuration is as follows:
 

 

[David Littell]

The flat line on the clock indicates the Slave is holding it low until the code indicates it should ACK the address.  Try to find some example Slave code with a more complete ..._AddrCallback().

[Andrew Neil]

Try to find some example Slave code with a more complete ..._AddrCallback().

+1

 

​@gocchan The Cube firmware packs for both STM32WBA and STM32U0 have examples of doing I2C between two boards:

https://github.com/STMicroelectronics/STM32CubeU0/tree/main/Projects/NUCLEO-U031R8/Examples/I2C/I2C_TwoBoards_ComIT

https://github.com/STMicroelectronics/STM32CubeWBA/tree/main/Projects/NUCLEO-WBA25CE1/Examples/I2C/I2C_TwoBoards_ComIT

 

You should be able to access these direct from CubeMX.

[LCE]

So slave clock stretching is enabled.

Check what the RM says about when this is done.

In the L07x I’m currently working with I have the ADDR interrupt activated, so the clock stretching ends and the correct address is ACK’d when clearing the ADDR interrupt flag, Check if this happens somewhere in your code.

			/* clear ADDRESS match flag
			 *	-> this ends CLOCK STRETCHING
			 */
			I2C1->ICR |= I2C_ICR_ADDRCF;

 

[gocchan]

As you commented, developing based on I2C_TwoBoards_ComIT achieved the objective.

Thank you.