Hey Jack, rx,tx were on the right pins ... but : 1. in arduino - one can write "if (Serial.available() >= 2)" , for the ZPUno the available() function is only showing if only one byte has arrived. (this is not documented). That is because the Fifo has only signals for full or empty. When I find time I will try to change that. 2. the 5V tolerant pins produced much interference to the data (first I tried them), and some weird error that I had to reset the FPGA by Hand after power up. 3. with pins 22,23 .... I managed the connections, but due to much interference and not a proper shielded cable I gave up on this Idea. The problem was I can not trust the data and have to implement some checksum . Maybe the UART is also too sensitive ? .. Filip