New APRS mechanism

This mechanism is quite clever, and can use either Analog/AX25 APRS, or APRS over DMR.

There are a few settings in different sections which need to be set to make it work. There are a few settings I haven't fully reverse engineered either.

For DIGITAL (DMR) APRS, important settings are:

Under DMR Service:

    "GPS On/off": "On", (Needs to be on otherwise gps receiver disabled)
    "GPS Interval": 0, (disables 'OLD' mechanism')
    "GPS Channel group ID": 9, (Irrelevant, part of old mechanism)
    "GPS Channel channel ID": 2 (Irrelevant, part of old mechanism)
},

Under the APRS section:

    "APRS": {
    "Manual TX interval": 0,  
    "Auto TX interval": 60,
    "Beacon": "GPS_LOCATION",
    _Ignore all the AX25 prefixed options, they don't apply to DMR_
    "DMR channels": [
        {
            "Zone ID": 65535,
            "Channel ID": 65535,
            "Call Type": "PRIVATE",
            "PTT": "OFF",
            "Report Slot": "TS2",
            "APRS TG": 234999
        },

Meanings:

• Auto TX interval: Updates every 60 seconds.

• Beacon: Location sent will be the current GPS location. There is a way to send a fixed location, but I havent fully decoded it.

• Zone/Channel IDs: If these are set to 65535, this DMR 'channel' will send its' data on the currently tuned channel. If a different Zone/Channel ID is specified, the radio will tune from the current channel to that one, send the update, then retune back.

• Call Type - PRIVATE or GROUP.

• Report Slot - TS1, TS2, or CURRENT

• PTT - ON, or OFF - whether position data sent every time the radio is keyed up.

• APRS TG: the DMR ID that the data will be sent 'to'.

So for the above, I have specified:

The updates will be sent on the current tuned channel, to the UK Brandmeister APRS talkgroup, as a private call, and will go out on TS2 (regardless of what TS the current channel is set to). This is pretty reasonable for a Brandmeister DMR-APRS update.

Under Zones/Channels:

For each channel you want APRS updates to go to, there is now a new attribute under that channel, called "APRS Channel"

It is set to a number between 0-8, which specifies which of the above-defined 'DMR APRS channels' the update will go out on. THey are 'numbered' in the order they are listed in the JSON file, being 1-8.

• 0 - no APRS or DMR-APRS update will be sent.
• 1-8 - specified DMR-APRS channel settings will apply to this channel
• 9 - an analog APRS update will be sent using the AX25 settings under DMR service (see below)

For AX25-APRS:

I havent written this yet!