intend to use TWI communication, added pull-ups ( 10k ) on SCL and SDA lines, DDRD = 0xFF, Vcc is 5V.
I am experiencing following problem with TWI: as soon as TWI starts; sending start bit; voltage drops down to appr. 2 V, no further action on either line occures ( checked with oscilloscope ). I've measured the current on SCL line and does not exceed 400 uA, so I'm far bellow 3 mA.
The pins are not dead, as if I use them as output pins, they work OK, swinging between 5 and 0 V.
please advise me,
with regards, Branko