In my current project we are writing a program to convert a newer protocol to an older one.
These conversion programs are being referred to as adapters, but the team cannot agree which spelling to use: adapter or adaptor.
I personally plump for adapter, as adaptor sounds like its a person (like actor, realtor, etc.) rather than a device.
Is there a case for using one rather than the other?
Both are commonly used and listed in dictionaries, but adapter (with an e) is usually listed as the more common – see, for example, Merriam Webster or the Cambridge dictionary. It’s not a strong basis for choosing one over the other, but it might be enough to settle the matter in your case :).