81 is latest firmware with 2.04 latest CPS.
I'm pretty sure there is something later than 3.17.81 but no one has found it yet. Their support sucks to put it mildly. I have several of their radios including the 770 and its been a nightmare to get support. I had to call the President of the company at one point to get what I did for two different radios. He was rather put out I'd bought them online rather than through authorized sources. Seems I should have spent 300 rather than 80 for a radio.
Go figure.
I've heard things about them going under or being bought by someone else and all US sales/support being pulled but unsure how accurate that is. The hoops I had to go through to get what I did are just not acceptable or worth it.
Stick with either CSI or Motorola in my opinion, I'm going to from now on.
Anyway good luck. Try Yahoo DP770 group too. I've found several updates there over time.