I got a problem, i want to connect two 16MHz AVRs by SPI or USART over upto 5m distance, and i want this interface running at the full speed. I let the master generate 8MHz clk through the Ribbon cable and check the waveform at the receiver side, and it was just so ugly. I connected then a coax (similar length) and the waveform was still bad. So do I need some special cable termination circuits or ICs to let the waveform back to sharp?
Any suggestions would be appreciated.