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

[Jannis Dohm]

Posted on June 05, 2018 at 14:20

Hello, 

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.#i2c-example #pmbus #stm32-i2c-smbus

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