Dual Displays and LoRa, the SnapOnAirDUO Is a Pager for the Times
By: Tom Fleet
Tags: Lora, Rfm95w, Pager, Internet of Things, Electronics Design

“Hello, anybody page Quinton?” is a line from a skit on the Pharcyde album, “Bizarre Ride II the Pharcyde.” This album came out in 1992, over 25 years ago.

With that in mind, it’s fair enough that a lot of younger people won’t know what a pager, or beeper, is, or even does.

The SnapOnAirDUO Pager

It can be hard to imagine a time without a mobile phone in the hands of nearly every person. Being able to make voice calls, send texts, or even multimedia to anyone you choose instantly, hasn’t always been the way of things. In the days before this, if you urgently needed to get in touch with someone, you could send a message to them via a paging service, to be shown on a little alphanumeric screen on their pager. Leave a contact number, and hope they call you back.

There were some advantages to the system, compared to the world of smartphones. Simplicity and battery are some good examples, and the ability to guarantee QOS with in-house transmitters (e.g. hospital use) is another.

Dr. Philippe Cadic (aka @PwavRobot) is resurrecting the idea of a pager for the modern age with a suite of projects under the moniker of “SnapOnAir,” and with one of the more recent project members, called the SnapOnAirDUO, he’s not skimping on the feature set either!

In a nutshell, the SnapOnAirDUO is a bi-directional, point-to-point (more on that later) text paging system, that uses LoRa radio as the data link. Manifest as a Feather shield, it is intended to take an ESP32 Feather board (TTGO-ESP32) to drive the show.

The LoRa radio modem is an RFM95 module, giving users the option to pick their countries LoRa frequency allocation, and perhaps most notable of the device is the choice to use two separate displays!

The main display is a 1.3" IPS display, with a ST7789 SPI interface controller. This full color display is used to show the bulk of the “pager” application (messages, etc).

A second, smaller (0.91") OLED is used for diagnostic information (RSSI, link parameters) and will host a virtual keyboard, to enable text entry without blocking the main application window.

So, what’s all this about point-to-point?

The main driving force behind this project is to provide a reliable means of communication, when there isn’t an existing infrastructure over which to communicate.

Some examples of such a use case include disaster response, where existing infrastructure may be destroyed, or inoperable. Others include areas where there was no existing infrastructure at all, such as rural or developing areas.

P-2-P vs. client server architecture

The pager system only requires the pagers themselves, configured to speak to each other as a point-to-point / peer-to-peer link. There is no need for a gateway or other central hub, as seen with a client-server model.

With two diminutive RFM9x modules doing the heavy lifting, you might have concerns about range, but with @PwavRobot reporting successful range tests of “around 1 km in urban areas”, this project is a great example of how practically useful LoRa radio systems are.

You can check out the SnapOnAir website, or Philippe’s GitHub for more details, and all the hardware files.