None of my mRo air radios have USB ports. They are my preferred brand, but that’s the down side.
@Awsmits, use an FTDI adapter. They are a dime a dozen on Amazon, Adafruit, Sparkfun, Mouser, DigiKey, etc.
However, I don’t think firmware is your problem. Check this out:
I just did EXACTLY what you did with a set of mRo radios. I updated the ground radio to v2.2 using Mission Planner’s local update feature, and it immediately reconnected to the air unit that was still running v2.0.
This post also discusses mixing firmware versions without significant issue.
I will update the air radio later, anyway. I’ll let you know how that goes.