Serial port

serial port device name is different from Ubuntu in kamikaze

serial port hardware is a little different, instead of normal 12v, we have 3.3v 

1- we can use a max232 to fix it and make is a standard port

2- we can use it directly to the circuit ( very difficult to debug)

**3- we can use a temporary converter test circuit, best choice

make a test application for serial port, to see if it works.

we connect the standard output from the test circuit to a PC, test the serial port output if ok.

copy the test function to the client application, check if all ok.

finish client.