A simple add-on for mobile phones to enable SMS-like messaging in a group when outside cell coverage, or in disaster scenarios.
This is a fairly simple add-on for mobile phones to enable SMS-like messaging in a group when outside cell coverage, or in disaster scenarios. It utilises Semtech LoRa radios, for low-power/long-range communications. There are a lot of hardware options, and I am still trying different devices and manufacturers, but for now this tutorial will show how to assemble and set up one of the following boards:
- TTGO ESP32 Lora with OLED
- Adafruit Feather M0 RFM96
TTGO ESP32 Setup
This board is quite nice in that it includes a nice OLED screen and Bluetooth radio. Unfortunately, the LoRa radio is not as good as the Feather, and only seems to get about half the range.
With this board you can choose whether to connect to handset via UDB OTG cable, Bluetooth Classic or Bluetooth LE. You simply flash the board with the appropriate firmware image (there are three different firmware binaries for each connection type).
- Flash the board with the Ripple firmware image: Follow ReadMe on GitHub
- Wire up battery and switch
- Wire up the piezo buzzer to GND and Pin 25
- Optional: 3D print the case
I have also designed a 3D-printable case for this, which you can download from here: https://www.thingiverse.com/thing:3865750
Adafruit Feather Setup
These boards are nice quality, but a bit more expensive. There is a bit more involved with these, as you need to do some more soldering to install a LoRa antenna.
- Flash the board with the Ripple firmware: Follow ReadMe on GitHub
- Wire up the piezo buzzer to GND and digital pin 11
- Solder a u.fl antenna connector to underside, connect antenna to u.fl
- Optional: 3D print the case. See here for the files: https://www.thingiverse.com/thing:3879020
(Optional) Soldering the Dipole Antenna
The 3D-printable case is designed for use with this dipole antenna: https://www.banggood.com/T-Type-900MHz-Long-Range-Receiver-Antenna-IPEX-4-for-FrSky-R9-Mini-R9-MM-p-1361029.html
It’s a good antenna, but doesn’t have the right connector, so you need to cut IPEX4 one off, then separate the coax braids and solder to the antenna ground pads (see end pic below). To do this, you need to strip about 10mm of the outer plastic off the end of the cable, then separate the very fine surrounding coax wire mesh then put some solder onto this. Then remove about 1mm of the plastic from the inner active wire and put a small amount of solder on this.
Next, pre-tin the antenna ground pads on the Feather, and the active antenna pad in the middle, then solder the antenna to these pads (separated coax to ground pads, active inner wire to antenna pad).
Read more: LORA MESH CHAT