Hopefully this puts into one place the relevant info for T-Deck users to get up and running. So far, the information has been spread over a number of posts, as the various features emerged. (NOTE: this guide is for the V4 firmware.)
Download
First download the firmware .bin from here.
Flashing
Please refer to this prior post about how to flash to ESP32 devices like the T-Deck.
IMPORTANT: This .bin is just for the application partition, so make sure you flash this to offset 0x10000.
NOTE: before flashing you need to put the device into DFU mode by pressing and holding down the trackball then press the small reset button on the left side of the device. (then release trackball) Then flash the firmware.
After flashing the .bin, you then need to press the reset button to reboot into normal mode.
GPS Wiring and Printing Case
T-Deck Plus users can skip this section. Installing a GPS is quite important, as it is the only way it can synchronise its clock to the current time. Having the location features is also very handy, of course.
You can either just use the 4-pin connector at the right-hand side, and have the GPS external, but is much neater to have the wiring inside. The four pins can be soldered on the back end of the plug:
With RX (white) going to the GPS's TX pin, TX (green) going to GPS's RX pin, then GND (black) to GPS GND, and VCC (red) going to GPS's VCC. Most GPS modules should work fine, like this cheap and cheerful one I usually use: https://s.click.aliexpress.com/e/_DlSpAg7
For more help with this step, this YouTube video has details of interesting cases and GPS options:
https://www.youtube.com/watch?v=tt_iNSs9G-g
UI Navigation
When you first run the firmware, a few help screens will be shown, which attempt to point out the UI paradigm this has. Originally, this firmware was design for much smaller screens, and with only a 5-way joystick-like interface. So, there are still scrolling concepts throughout the UI. The trackball on the T-Deck maps naturally to this, but you can also use the touch screen, by single taps in the 4 quadrants shown (left, right, top, bottom).
So, generally there is up/down scrolling, with right to select, or go into sub-screen, and left to go back to previous screen. Some screens require the ENTER key on the keyboard to finalise/commit the action.
Some screens also have a context menu, and there is usually an icon indicating this in the titlebar (top-right), although on the home screen this is bottom-left. You can either tap on the icon, or long-press anywhere, or press SHIFT+zero on the keyboard.
The screen is turned on/off by clicking the trackball in.
Initial Config
First, you need to pick a centre frequency and spreading factor for the LoRa radio. All of the devices in your mesh need to use the same radio params. A general rule for the spreading factor is: higher = longer range, but longer time to transmit. An increment of 1 to the SF doubles the time it takes to transmit a packet. For a more densely packed mesh, where nodes are relatively closer to each other, a smaller SF is better. For sparse mesh, higher SF. The default of 10 is usually a reasonable value for most meshes, although I have found 9 to be pretty good without losing much in the way of range, but getting 'snappier' responses. (especially when number of hops exceed 5)
Go into the Setup menu, then scroll down to the Radio menu. In the next two screens, select the frequency and SF. Press ENTER at final screen to commit. Reboot the T-Deck.
The next step is to assign unique IDs to each device in your mesh. These are numbers in the range 2..250. (ID of 1 is reserved for an optional admin who uses the Ripple Commander app). Go into Setup again, then select Identity. In the next two screens enter the ID and a name/callsign for this device. Again, after pressing ENTER on last screen to commit, reboot the T-Deck to apply.
Next select the timezone you are in, again under the Setup menu. You enter this as 'minutes from UTC', with negative being West of London, positive being East of London. This is important as the clock is synchronised from the GPS as just the UTC time, so the device needs the timezone offset whenever displaying dates and times. (like at the top of the home screen)
Adding Contacts
This can be done at any time. All communication is encrypted, so you need to do a key exchange with each user you add. When the T-Deck is first run, a public/private key-pair is generated, and the public part needs to be given to other devices.
There is a special 'chatroom' for this, and is accessed via the Setup > Exchange Keys menu. A special channel is created for this, and encrypted with a temporary 4-digit pin code. The pin code can be anything, but you just have to enter the same pin into each device and enter the Exchange room.
When the top item ('My Details') is selected, press ENTER (or trackball right) to send your ID/name/public-key to any others in the room. The other devices should then see this added to the list. Scroll down, then ENTER (or trackball right) to add that device/user to your contact list.
NOTE: this exchange needs to be two way! ie. A sends key to B, B sends key to A.
Once finished, go back to home screen, and is advisable to reboot the device.
Conversations
From the home screen, just scroll down, then right to go into the conversation screen for that contact. Simply start typing and you should see your message being composed below the horizontal line. Press ENTER to send. The text will flash while trying to send. If it successfully reached the recipient, the text moves up into the conversation list, but if it times out then stops flashing and text stays in the input area.
Upon entering this screen, a small 'ping' is sent to the recipient's device, and if they are online and reachable, then a small orange wi-fi icon is displayed in the top-right. The titlebar will also cycle through showing the name and the GPS location of the user/device. You can also open the context menu, and select Show on Map to centre the map on their current location.
The screen now has two different display modes: timestamps on, timestamps off:
Location
If you open the home screen's context menu, there are system-wide settings available here, like Sound preference. There is also a GPS Location item. Scroll down to this, then trackball right will cycle through 3 options: DENY, ALLOW, BROADCAST.
If you don't want your contacts to know your location, select DENY. If you do, then select ALLOW. The BROADCAST option will constantly broadcast your location whenever you move (currently, when more than 20 meters), and no more than once every 10 seconds.
Maps
The home screen has two tabs, which you can switch between using the two icons on the left-hand side. You can also press the spacebar to toggle between list/map.
The map tab will just be black if you have no map tiles on your SD card (or no SD card). The map tiles are expected in the popular scheme of 256x256 PNG files, used by Google and OpenStreetMaps, among others. You need to download tile sets yourself.
The number of tiles needed really balloons out fast with each zoom level, so you need to be selective which areas to download. Alberto Cajiao has kindly donated a Python script you can run on your laptop for downloading tiles via the Thunderforest API: https://github.com/fistulareffigy/MTD-Script
The Ripple firmware just expects the map tiles to be on the SD card in the following file/directory scheme: /tiles/{zoom}/{x}/{y}.png
Make sure the SD card is using the FAT32 format, and seems to be better if it is 32Gb size or smaller.
Map zoom/pan
You can pan the map around either by using the trackball, or with touch screen swipe gestures (left, right, up or down). There are two on-screen zoom buttons on the right-hand side (+) and (-). You can also zoom in/out by pressing the S and W keys.
Your current location is rendered as a blue dot on the map, and is updated live.
If you are in a car (or plane!) and want a moving map you can toggle the 'tracking' on/off with the top on-screen button. It will turn orange when enabled. The map will automatically refresh as your GPS position nears an edge of the screen.
Other contacts, whose location has been received, are also rendered on the map as orange dots. These will move and show live location if they have the BROADCAST option enabled. You can tap on the orange dots to go straight into the conversation screen.
Custom Sounds
At present there are two sounds that are played, the startup and alert sounds. These can actually be customised by placing an mp3 file onto the SD card. Just put a file named startup.mp3 onto the card for custom startup sound. Similarly, just place a file named alert.mp3 for custom (incoming message) alert.