I2C Communication on STM32 fails with Digital Analog Converter
I solved it by adding this code in the main() loop. I checked what got send on the arduino with a logic analyzer.
    HAL_Delay(100);
    uint8_t test[1] = {0x80};
    uint8_t data[2] = {0x00,0xFF}; // Change 2nd Decimal to Analog output you need
    uint8_t data2[2] = {0x00,0x7C}; // Change 2nd Decimal to Analog output you need

    status = HAL_I2C_Master_Transmit(&amp;hi2c1, 0xc4,test, 1, 10);
    status = HAL_I2C_Master_Transmit(&amp;hi2c1, 0xc4,data, 2, 10);
    HAL_Delay(500);
    status = HAL_I2C_Master_Transmit(&amp;hi2c1, 0xc4,data2, 2, 10);
    HAL_Delay(500);