Building a LoRa Sniffer with an Adafruit Feather M0

You’d be forgiven for not being familiar with LoRaWAN (Long Range Wide Area Network) technology as it hasn’t been widely adopted by the masses. The goal of LoRa networks is to bridge the gap between cellular networks, WiFi, and Bluetooth, by creating a mesh network that operates in an unlicensed frequency of the radio band. It’s being pushed by the LoRa Alliance as a way to get Internet of Things devices connected at a low cost.

When Joe Broxson heard about LoRa, he was intrigued. But, because it’s a mesh network, LoRa needs other devices to connect to — ideally a lot of them. If you were to build a LoRa device, data would need to jump through an unbroken chain of other LoRa devices in order to reach a central server and hop onto the internet. A single LoRa-based IoT widget would be useless, because it’d have nothing to connect to.

So, how could Joe determine if making LoRa devices was even worthwhile in his area? By building a LoRa network sniffer to see how much traffic is being passed around in his neighborhood. For the base of his sniffer, Joe used an Adafruit Feather M0 with a 900mHz RFM95 LoRa Radio. Because the it’s part of Adafruit’s awesome Feather line of products, he was able to easily add a TFT display FeatherWing and Lithium Ion battery pack.

He packaged all of this in a nice a basic 3D printed case, and got to coding. Joe already had a lot of professional experience programming the Cortex M0 that the Feather M0 is built on, so this part was right up his alley. His software scans the proper frequencies, and scrolls through any discovered packets on the TFT display, as well as logs them to an SD card. Now Joe can leave his LoRa sniffer sitting at home, or take it with him, in order to get a feel for the size of the LoRa network in his area.