I've got a piece of code running on an Arduino board that will accept ASCII text commands on its serial port, and then will switch some relays based on which text commands you send it.

I need to be able to run an automation script or batch file (on Windows XP and later only) that will switch the relays under certain conditions during an overnight test run.

I have this all working, in that I can connect a serial terminal program to the COM155 port that the Arduino is connected to, and type the commands into the terminal program, and it will accept the commands and will work.

Is there a super-simple way to send these commands from the DOS prompt or from a DOS batch file or a vbscript? I've tried COPY and ECHO... those just create a file on the hard disk called "COM155" when I try it.

Uncle google isn't helping me here. I do searches, and the results always talk about using PUTTY and typing things live. I want to automate this. Or, the search results say to use COPY or ECHO, and of course, I tried that and it just makes a hard disk file named COM155.

I know that I could just compile an EXE file to use as a stub program that will handle the necessary details of opening the COM port, sending the command, and closing the COM port. But I'm trying for a quicker, simpler solution here without having to get into an extra layer of C code just to get this one simple thing done.