Packet Radio Boards

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If you want wireless communication between microcontrollers, you almost certainly want boards with integrated packet radio.

The RFM69 modules have a working range of 100m with a clear line-of-sight connection. The RFM95 LoRa modules work out to about 500m under normal conditions, and have been tested at 2km with focused antennas.

The data rate for both kinds of radio is about 19.2kbps (about 1.8 kilobytes per second).

Adafruit makes processor boards with on-board radios that work in the 433 MHz and 900 MHz bands.

In general, higher frequencies are more prone to scattering and lose more energy passing through objects, so 433MHz radios are a bit better at long-distance connections and connections where you don't have a good line of sight from one antenna to the next.

433MHz radios are more prone to interference from high-speed USB signals (operating at 480MHz) though, and high frequencies make it easier to modulate signals. That makes the 900MHz radios perform a bit better in areas where there are a lot of other signals.

Adafruit has Feather boards with ATmega32u4 and SAMD21 microcontrollers for both frequencies and both kinds of modulation.

Double check the legal broadcast frequencies for data radios in your country. They may vary and you do not want to use radio signals in a frequency band where the authorities do not want you communicating or in a band used by cellular or emergency services only.
IMPORTANT NOTE: The packet radio modules use SPI to communicate with the microcontrollers. On these Feathers, the radio module's CS pin is tied to GND with a pull-down resistor so the radio is active by default. If you want to use another SPI device, like an SD card, YOU MUST SEND GPIO PIN 8 HIGH FIRST!

433 MHz Boards

 

In general, higher frequencies are more prone to scattering than low frequencies, and lose more energy passing through objects.

 

433MHz radios are a bit better for long-distance connections and connections where you don't have a good line of sight from one antenna to the next.

900 MHz boards

 

High frequencies make it easier to modulate signals, and to identify signals in a noisy environment.

 

900MHz radios perform a bit better in environments with interference, especially signal leakage from 480MHz high-speed USB signals.

This guide was first published on Nov 07, 2018. It was last updated on Nov 07, 2018. This page (Packet Radio Boards) was last updated on Apr 21, 2019.