Support for other Fender LT amps

[brentmaxwell]

I only have a Mustang LT25, and I suspect there are differences among the other amps in the series.

The other amps are:

• Mustang LT50
• Mustang LT40s
• Rumble LT

To ensure compatibility, all that would be needed is a Wireshark dump. To make sure it covers everything, I would want the dump to include:

• power on and connection
• pressing the footswitch
• setting footswitch parameters
• setting line out gain (if applicable)
• turning all the knobs and pressing each button
• enabling and disabling the tuner

From that, it would be trivial to double check the protocol messages for any differences that need to be accounted for in the code.

[tim-littlefair]

Brent, I have an LT40S, and I would be interested in helping.

I catpured wireshark dumps for power on/connection and some other operations about a year ago, please find these attached. Sorry, I don't have the footswitch.. I don't have the VM I used to capture these set up at the moment, but may be able to get this up and running again some time before the end of the year.
LT40S-captures-230903.zip

I have done some work on a fork of Offa's github repo of the original Debian 'plug' program. This can connect and retreive all of the preset data, but I've become convinced that the differences between V1/V2 protocols and the LT protocol are too major for a pull request to Offa's repo to be mergeable and maintainable. In particular, the data which needs to be serialized to represent an LT preset is not round-trippable into the V1/V2 storage format implemented by plug.

The most capable branch of my fork of plug is here if you are interested:
https://github.com/tim-littlefair/plug/tree/LT40S-support-1019
I'm hoping to be able to add the capability to switch the active preset from plug, but if I can get that feature working I'll stop work on the fork as I don't think loading preset data from the filesystem, editing it, saving it or sending it to the amp are feasible without changing the plug V1/V2 serialization format and I don't want to do anything which might adversely affect plug users who have already-supported V1/V2 devices.