Using a Feather 32u4

If you're using a feather with a small flash size (like the Feather 32u4), you'll need a smaller library to experiment with than the one in this guide.

Enter TinyLoRa, an Arduino Library for Feathers and arduino-compatibles using the HopeRF RFM95/96W module. It's less than 8kB, making it perfect for smaller chips! It's also compatible with the Feather M0 LoRa, in case you want a smaller communications library for your speedy M0.

One of the trade-offs of using this tiny library (compared to a more featured library like the MCCI-LMIC Library) is that it uses a different method of device registration, Activation-by-Personalization (ABP). Instead of performing a secure join procedure, the security keys are hardcoded into the Sketch and "burned" into the Feather during compilation. 

Parts

First, let's gather the parts required for this project.

Adafruit Feather 32u4 RFM95 LoRa Radio- 868 or 915 MHz

PRODUCT ID: 3078
This is the Adafruit Feather 32u4 LoRa Radio (RFM9x). We call these RadioFruits, our take on an microcontroller with a...
$34.95
IN STOCK
1 x DHT22 Temperature + Humidity Sensor
The DHT22 is a basic, low-cost digital temperature and humidity sensor.
1 x Breadboard
Half-Sized Breadboard
1 x Breadboard Wires
Breadboard Wiring Bundle

Wiring

Next, let's wire up our circuit. 

Your Feather does not come with an antenna, but there are two ways of wiring one up.

 

For this guide, and to keep the build cost-effective, we soldered a small, 82mm wire to the ANT pad.

 

  • Antenna Options and installation instructions are detailed on this product's learn guide's antenna options page. 
  • Note: Antenna length differs between regions, make sure you cut the antenna to the correct length for your region.
When wiring the Feather 32u4, there is NO jumper between Pin 6 and IO1 as shown in the Feather M0 LoRa wiring diagram. 

Make the following connections between the Feather 32u4 and the DHT22:

  • Feather 3V to DHT22 Pin 1
  • Feather Pin 10 to DHT22 Pin 2
  • Feather Ground to DHT22 Pin 3
  • Add a 10k ohm resistor between the DHT22's VCC (DHT Pin 1) and Data Pin (DHT Pin 2).
This guide was first published on Sep 21, 2018. It was last updated on Sep 21, 2018. This page (Using a Feather 32u4) was last updated on May 19, 2019.