I2C1, STM32F746 does not work with Wire Library

[epikao]

Hello, I tried everything, but the I2C1 ( PB8 -> I2C1_SCL and PB09 -> I2C1_SDA ) with the Wire library does not work.
Measured with a logic analyzer the I2C lines are always high.

What's wrong :-( ?

See code below:

TwoWire Wire2(PB9, PB8);

void setup();
{
  pinMode(PB9, INPUT);  // remove internal pullup
  pinMode(PB8, INPUT);  // remove internal pullup
  Wire2.begin();
}

void loop()
{
          Wire2.beginTransmission(0x38);
          Wire2.write(0x00);
          Wire2.endTransmission();
          delay(20);
          Wire2.requestFrom(0x38, 30);

          for(uint8_t i=0;i<=15 && Wire2.available(); i++){
              buffer[i]= Wire2.read();
              Serial6.println(buffer[i]);
              
          }
}

Thank you

[ABOSTM]

Hi @epikao,
You initially configure PB9/PB8 as I2C (Alternate function), with
TwoWire Wire2(PB9, PB8);
Fine, but in then in setup() you configure those pins as input so implicitly they are configured as GPIO (and no more configured as I2C)

pinMode(PB9, INPUT);  // remove internal pullup
pinMode(PB8, INPUT);  // remove internal pullup

By the way, by default, I2C pins are configured without internal pullup (thus requiring external pullup) so you don't need to remove internal pull up.

So just remove those 2 lines and I hope that would be good.

pinMode(PB9, INPUT);  // remove internal pullup
pinMode(PB8, INPUT);  // remove internal pullup

[epikao]

So just remove those 2 lines and I hope that would be good.

pinMode(PB9, INPUT);  // remove internal pullup
pinMode(PB8, INPUT);  // remove internal pullup

Thank you. Initially I did not include these two lines, but with or without, both i2c lines remain constantly high. No clock or data measurable.

[epikao]

Hello, I have found the error. Although the display manufacturer states PB8 and PB9 as the I2C port, this is not true, it is PH8 and PH7.
I do not understand, but it works...