rfm69

RFM69 native packet mode driver

Instructions (Arduino)

• Include the library by adding following headers to your sketch:

#include <SPI.h>
#include <SpiDevice.h>
#include <Rfm69.h>

• then declare an instance of the RFM69 radio driver:

Rfm69<SpiDevice<10> > rfm69;

• Here the SpiDevice represents the SPI device abstraction of the attached RFM69 radio. In this case for example the radio was attached to the SPI bus with the Slave Select line connected to Arduino digital pin number 10. See also the library SpiDevice.
• The initalisation routine takes as arguments the Node ID, the Group ID, and the Transceiver Frequency. For example following code will setup Node ID = 28, Group ID = 42, and Transceiver Frequency = 868,6MHz:

rfm69.init(28, 42, 8686);

• The Node ID can range from 1 to 60. Node ID = 61 is for send only nodes. Node ID = 62 is reserved, and Node ID = 63 is for receive-everything nodes.
• An PSK encryption can be set up by calling rfm69.encrypt(myPassword) with a string myPassword of 1 to 16 characters. Calling rfm69.encrypt(0) will disable encryption.
• Transmit power can be modified by calling rfm69.setTransmitPower(myPower) where myPower is a value ranging from -18dBm to +13dBm for RFM69W models and from -2dBm to +20dBm for RFM69HW models. +13dBm is the default power setting for both models. The functions returns either stdlib.h EXIT_SUCCESS or EXIT_FAILURE if the power setting is outside of the limits. To enable the higher power settings for the HW modules at the declaration must be appended either Rfm69ModelHW or Rfm69ModelHCW. For example:

Rfm69<SpiDevice<10>, Rfm69ModelHW> rfm69;
rfm69.setTransmitPower(+17/*dBm*/);

• Pay attention that the +20dBm power setting may be not legal in your country. Please check your regulations for telecomunications.
• Sending and receiving methods allow up to 62 bytes of data. The special header byte is normally set to 0. It encodes in bits from 0 to 5 either the destination or origin Node ID and in bits from 6 to 7 some status flags.

Instructions (WiringPi)

• Make sure that the SPI module is either enabled in the Device Tree and/or loaded by the current Linux kernel, ie. not blacklisted. For example on Raspberry Pi:

cat /boot/config.txt | grep "^dtparam=spi=on"
dtparam=spi=on
cat /etc/modprobe.d/raspi-blacklist.conf
#blacklist spi_bcm2708

• Install WiringPi either with sudo apt-get install wiringpi or sudo pacman -S wiringpi.
• Compile the RFM69 library with g++ and -lwiringPi.
• Linux kernels less than version 4.1.x may require root for execution.
• The declaration of the SpiDevice class is nearly identical as for the Arduino except that the first template parameter is used instead to describe the selected SPI channel. For example channel 0 is SPI bus with CE0 pin, channel 1 is SPI bus with CE1 ect. it is not the actual Slave Select GPIO pin as it is used in the Arduino implementation.

Hardware

• The RFM69 radio needs at least to be connected to the SPI pins 3.3V, MOSI, MISO, SCK, NSS, and GND. Beware that in transmit mode the HW/HCW module can consume up to 130mA from the 3.3V power supply. See also the RFM69HW Datasheet.

• Beware that the high power setting with +20dBm transmit power may be not legal to be used in your country. Please check the regulations for telecomunication of your country.

Further reading

• http://www.hoperf.com/rf_transceiver/modules/
• http://jeelabs.org/book/1513d
• http://jeelabs.org/book/1522c
• http://jeelabs.org/wp-content/uploads/2015/05/20/rfm69-on-raspberry-pi
• http://jeelabs.org/2015/05/27/rfm69-on-atmega/
• http://blog.andrehessling.de/2015/02/07/figuring-out-the-power-level-settings-of-hoperfs-rfm69-hwhcw-modules/