MikePooh

If I understand correctly PA11 and PA12 are connected to +3.3V through 2.2k resistor on Orange Pi PC Plus. That means that it is impossible to use internal pull-up.

I switched mentioned pins to IN mode. And it is seems they are pulled up by default. +-----+-----+----------+------+---+-Orange Pi+---+---+------+---------+-----+--+ | BCM | wPi | Name | Mode | V | Physical | V | Mode | Name | wPi | BCM | +-----+-----+----------+------+---+----++----+---+------+----------+-----+-----+ | | | 3.3v | | | 1 || 2 | | | 5v | | | | 12 | 8 | SDA.0 | IN | 1 | 3 || 4 | | | 5V | | | | 11 | 9 | SCL.0 | IN | 1 | 5 || 6 | | | 0v | | | If physically connect that pins to the ground it shows 0 level. But I need it 0 by default. All other pins which are not related to I2C/TWI I can easilly pullup/pulldown, but these not. i2c0 is disabled in armbiaEnv.txt Thank you.