UART connection using PL 2303. Weird characters
Serial ports are always hard to work with if you don't know what speed they are operating at. You need to somehow definitively determine the speed of the serial port, find it in a manual, get it from the manufacturer. You also need to determine if the port is using hardware control, if you have the correct number of stop bits, the number of data bits. Get a cheap oscilloscope, and learn about serial waveforms and you can debug the port that way. A serial analyzer might help, but usually you have to know the speed, stop bits, data bits ect. You could also try every combination but if you don't know what the port is sending then it could look like random garbage but actually be a bit stream.