I am trying to write a program to talk to a Watlow F4 series controller through a ICS GPIB to RS232 converter card, model number 4894A. The actual Watlow controller uses the ModBus protocol, which requires me to encode all of my commands in Hex. What I'm trying to do is send a command on the GPIB bus, and then read a response. The command will look something like this: 010300000001840A (In hexadecimal). I would then like to read the response, which will also be coded in hexadecimal. I'm using C/C++, so any examples of how to send hex commands on the GPIB bus to the Watlow controller would be great. Any info, links, etc. would also be greatly appreciated.