You should be able to use whatever version of the firmware is on the phone…
You just change the version line in your skinny.conf to match what is on the phone;
; Typical config for 12SP+
[color=orange]version=P002G204 [/color] ; Thanks critch
line => 6886 ; Dial(Skinny/6886@Gervais)
The version of the firmware is displayed on the phone when it boots (on the top line at the far right) or by pressing “*”
I have two 12SP+ phones that I use this way. They worked great with asterisk 1.0 (although with limited functionality). I have upgraded to asterisk 1.4 and am having trouble with my phone system… Lots of changes to configs and extensions.conf
If you actually find a firmware upgrade, I’d like to try to upgrade my old phones, so let me know.