Taking Things Too Literally

David Thomson, Original Code Consulting, August, 2019

I was interfacing to a vacuum pressure gauge from a major manufacturer recently and came across a surprising protocol. An example of the instrument's response to a data query is "@253ACK9600;FF". The "@" is an attention character. "253" is an address. "ACK" indicates that the query was processed without error. And "FF" is the termination. Pretty standard stuff, right? Except "FF" isn't "0xFF", as one might expect. It is two of the characters "capital F" in a row! And "ACK" and "NAK" aren't ascii 0x06 and 0x15, but are actually the letters "A", "C", "K" and "N", "A", "K"! So I'm not sure if this protocol was created by a beginner trying his/her best to follow typical practices, or if it was someone's idea of a joke!