• Radomir Dopieralski's avatar
    extmod/machine_i2c: Add clock stretching support. · ec078af9
    Radomir Dopieralski authored
    When the clock is too fast for the i2c slave, it can temporarily hold
    down the scl line to signal to the master that it needs to wait. The
    master should check the scl line when it is releasing it after
    transmitting data, and wait for it to be released.
    
    This change has been tested with a logic analyzer and an i2c slace
    implemented on an atmega328p using its twi peripheral, clocked at 8Mhz.
    Without the change, the i2c communication works up to aboy 150kHz
    frequency, and above that results in the slave stuck in an unresponsive
    state. With this change, communication has been tested to work up to
    400kHz.
    ec078af9