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STM32F746 Using HAL_I2C_Master_Transmit_IT/HAL_SMBUS_Master_Transmit_IT fails (SCL keept low after ack bit)

Question asked by Jannis Dohm on Jun 5, 2018


I'm trying to communicate between a STM32F746G Discovery Board and a Powersupply (over PMBus).
While doing so i realized that the SCL wire is kept low after the ACK Bit of the Powersupply.
To eleminate possible mistakes on the Powersupply side I switched to a STM32F769 Discovery Board as a slave and used the "I2C_TwoBoards_ComIT" Preject from the STM32Cube_FW_F7_V1.11.0 on both boards.


I only changed the "I2C_ADDRESS" on line 54 to 0x9A on both boards, the "
I2cHandle.Init.AddressingMode = I2C_ADDRESSINGMODE_7BIT" an both (line 110) and set MASTER_BOARD to comment on the STM32F769. 


the result is still, a low SCL line after the ACK bit. 


I tried using HAL_I2C_Master_Transmit() and everything works just as it should i can even write data to the Powersupply.

Any help is welcome.

I Added a picture of an oscilloscope showing the BUS.