I2C2 SCL is always high while SDA is sending data in NUCLEO-G031K8

[lbapplem]

Hi experts:

    I’m working on NUCLEO-G031K8 trying to use its I2C2(I2C1 is OK),I set PA11/PA12 as SCL/SDA, pull-up, OD, when I tried to read data, I found SCL is always high, but SDA has datas, I can’t figure out what’s missing, can you help me with that?

Bill

 

[David Littell]

1. Don’t rely on the MCU-internal pull-ups for I2C - use real resistors close to the MCU’s SCL and SDA pins.  4K7 or 10K should be fine for 100kHz or less and normal (on-board) distances.
2. Verify the pin configuration - you certainly don’t need a “very high” rate in the settings.
3. Confirm that the SCL and SDA pins aren’t connected to something else on the Nucleo.
4. Andrew always (with good reason!) wants to see a photo of your setup.

[TDK]

It looks like you are using a sampling rate that is too slow to see what is on the line. Perhaps use an analog capture. Show wiring. Ensure you are actually monitoring the pin you think you are. Toggle the pin as a GPIO output and view on the scope to verify that it can be toggled and is not shorted high.

[padawan]

I am thinking about the PA11(PA9) .

is there anything on PA9? Is PA9 an outputpin?

i can’t get an schematic of this nucleo board.

But on L412KC we have to remove two jumpers on the board to get it work with 

SPI and I²C

just my 2 cent

padawan 

[Andrew Neil]

i can’t get an schematic of this nucleo board.

As always, the schematics are on the ‘CAD Resources’ tab of the board’s Product Page:

https://www.st.com/en/evaluation-tools/nucleo-g031k8.html#cad-resources

[padawan]

Hello Neil,

palm to face.

i looked at “Dokumentation”.

Okay in the view of stm its “(E)CAD.

The schematic schows no link between PA9 and PA11.

I wonder whats the PA11(PA9) in the GPIO settings…

padawan

[Saket_Om]

Hello ​@lbapplem 

Please use the configuration below in your code :

    __HAL_RCC_GPIOA_CLK_ENABLE();
    /**I2C1 GPIO Configuration
    PA11     ------> I2C1_SCL
    PA12     ------> I2C1_SDA
    */
    GPIO_InitStruct.Pin = GPIO_PIN_11|GPIO_PIN_12;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_OD;
    GPIO_InitStruct.Pull = GPIO_PULLUP;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
    GPIO_InitStruct.Alternate = GPIO_AF6_I2C2;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

    /* Peripheral clock enable */
    __HAL_RCC_I2C2_CLK_ENABLE();

 

[David Littell]

Once again, DON”T USE THE INTERNAL PULLUPS FOR I2C.

[Andrew Neil]

​@David Littell 

Confirm that the SCL and SDA pins aren’t connected to something else on the Nucleo

 

​@TDK 

Ensure you are actually monitoring the pin you think you are

 

​@lbapplem Indeed - which was the initial problem here: