Typie-Walkie with LoRa and E-Paper Screen
This project is a variant of the Typie-Walkie E-Paper Screen. The radio of the initial project, WiFi, does not match with the low-power features of the e-paper screen.
Looking for another radio, LoRa came up for short messages over long distances. The boards are the iLabs Challenger RP2040 LoRa: they combine a RFM95W-SX1276 sub-1 GHz radio with an RP2040 MCU.
The touch e-paper screens were sampled by Pervasive Displays. The Challenger boards were bought at The Pi Hut.
The application is identical for the two devices.
The libraries for the screen remain unchanged. The Pervasive Displays Library Suite manages all the elements of the interface:
The keyboard contains three sets of keys: capital letters, lowercase and symbols.
Additionally, the § key changes the layout, and the « key acts as backspace.
The management of the LoRa radio was supposed to be easy thanks to the off-the-shelves Arduino LoRa library. Alas, it wasn't the case.
Too many messages were lost, whatever the options used with or without interrupts and callbacks. By luck, the RP2040 features two cores: dedicating each one to a specific task solved the problem.
The SDK also brings useful tools like mutexes to avoid collisions on the serial port. Those tools were encapsulated as objects to match the syntax of the Galaxia library.
Compared to other sub-1 GHz solutions (like the Texas Instruments CC1310, CC1350, CC1312, CC1352), the iLabs Challenger RP2040 LoRa doesn't provide the same level of integration. One core of the RP2040 is dedicated to the radio to avoid losing messages.
Compared to MQTT, LoRa doesn't provide the application layer: it needs to be developed with proprietary solutions.
The LoRa radio is consistent with the e-paper technology to bring a truly low-power solution.
Posted: 12 Aug 2022