librfm69

About

Static avr-libc library providing basic support for RFM69 radio modules.

I'm impressed how well these radio modules work; the range achieved with simple wire antennas as well as the reliable packet transmission.

This is work in progress. Currently available is:

Transmit a packet
Blocking receive a single packet with timeout
Async'ly receive a packet (MCU sleeps or does something else until reception)

Usage

Include librfm69.h and librfm69.a in the project
Implement the _rfm* functions in librfm69.h in the application (this is to make the library device and CPU frequency independent)
Route interrupts occurring on DIO0 and DIO4 to rfmIrq()

Range

There is a range test with an RFM95 in FSK mode at librfm95.

Susceptibility to Temperature Changes

With the default frequency deviation of 5 kHz and receiver bandwidth of 10.4 kHz, packet transmission is very unreliable and fails completely for me when the temperature of the transmitter is below 10°C and above 40°C, while the receiver temperature is at 20°C. The receiver does not seem to be prone to temperature changes.
Increasing frequency deviation to 10 kHz and receiver bandwidth to 20.8 kHz, temperature susceptibility is eliminated; when testing with transmitter temperature from -20°C to 50°C, packet transmission is perfectly reliable.

Frequency Deviation = 10.4 kHz (transmitter)
RegFdevMsb = 0x00
RegFdevLsb = 0xa4

Receiver Bandwidth = 20.8 kHz
RegRxBw = 0x54

The issue can probably also be solved with automatic frequency correction (AFC).