Hello list, I'm newbee so excuse me for my very basic question. I follow all the instructions on srlabs.de/gprs given by Karsten I have a C123 and a USB / jack 2.5mm - pl2303 based :( All steps are fine until I try to programm the compal ram ;) ./host/osmocon/osmocon -m c123xor -p /dev/ttyUSB0 ./target/firmware/board/compal_e88/layer1.compalram.bin I get : ... PROMPT1... ... PROMPT2... handle_write(): xxxx bytes (xxxx/yyyy) ... ... handle_write(): xxxx bytes (xxxx/yyyy) Received 1 byte : xx Received 1 bytes : yy ... ... Finally I received e.r.r.o.r (byte by byte) NOT ACK RECEIVED... I can also get (not with the same firmware...) : ... PROMPT1... ... PROMPT2... handle_write(): xxxx bytes (xxxx/yyyy) ... ... handle_write(): finished and then... nothing... I'm going to test the cable, as Philipp has told to Pavel. I also bought a RS232 / Jack unlocking Motorola (C123) cable and I own a BlackBox FTDI based USB/RS232 cable... So I'll test it as soon as I receive the cable. Do you think is a matter of cable, who is supposed to be osmocom compatible, or a phone issue or even the USB port... ? Thank you very much for your help and excuse me again with this kind of 'stupid' question about cable. I read almost all the subjects, I did a lot of experimentations in a lot of git branch (master, testing, burst_ind - of course not working with PL2303 ... + d1cb8ea9b784c7acbafbb2fdcedbdf4655c2f6f5 not working too) I think it must work at least in the master branch... Smith