I have a new problem and I can't find what I'm doing wrong. This is the receiver board and I use PORTD,6 to keep a 100k resistor to ground. Even though I put PORTD to O/P:s, they are still in high impedance mode, proved by injecting an AC signal (via 10k resistor) to port pin, looking with the oscilloscope AC signal at test point. This hi-z mode cause the rcvr to refuse ack-ing and making a hysterical transfer. By grounding the port via 10k everything works OK, receiving the sequence on LED:s 75,75,75,75,01,0E,30,00,40,10,08 as expected according to transmission and the rcvr software.