rfm9x

Introduction

Node.js module to interface with RFM9x LoRa wireless modules. Intended for use with Adafruit Radio Bonnets.

The code has only been tested on Raspberry Pi but could technically also work on other boards supported by onoff and spi-device.

Acknowledgements

• The CircuitPython RFM9x module was used as a template for most of the logic.
• The spi-device and onoff modules by fivdi made interfacing with the hardware really easy.

Example

See example/pingpong.js for a simple example of receiving and sending data.

API

The modules exports a single class RFM9x.

Class RFM9x

Class representing the LoRa module. The constructor requires no arguments.

const rfm9x = require('rfm9x');
const module = new rfm9x();

await module.init({ ... });

---

Properties

• debug - Output SPI debug information

debug

Set this property to true to get all SPI communication printed out to the console.

Note: Because console.log() calls are synchronous in most circumstances, enabling this can impact timing! For example, it might cause switching from sending to receiving mode to be slow enough to miss responses from other nodes.

---

Methods

• init(options) - Initialize module and LoRa settings
• startReceive() - Put the LoRa module in receive mode and enable the receive event
• stopReceive() - Put the LoRa module in standby mode and stop receiving packets
• send(payload) - Send a packet via LoRa
• getVersion() - Get the chip version number from the module

init(options)

• options - Options object (see below). All properties are optional, default values will be used when omitted.

Initialize module and LoRa settings. Needs to be called before using any of the radio functions.

Returns a Promise that resolves with no value.

The following options are supported:

• frequencyMhz - Base frequency in MHz, default: 915
• preambleLength - LoRa preamble length in bytes, default: 8
• bandwidthHz - LoRa bandwidth in Hz, default: 500000
• codingRate - LoRa coding rate, valid values are 5 (4/5) to 8 (4/8), default: 5
• spreadingFactor - LoRa spreading factor, valid values are 6 to 12, default: 7
• enableCrcChecking - Whether to enable CRC checking on incoming packets, default: false
• txPowerDb - Transmitter power in dB, valid values are 5 to 23 (currently only high power mode is supported), default: 23
• enableAgc - Whether to enable Automatic Gain Control, default: false
• resetPin - Number of the GPIO pin that the RFM9x RESET line is connected to, default: 25
• dio0Pin - Number of the GPIO pin that the RFM9x DIO0 line is connected to, default: 22
• dio1Pin - Not currently used. Number of the GPIO pin that the RFM9x DIO1 line is connected to, default: 23
• dio2Pin - Not currently used. Number of the GPIO pin that the RFM9x DIO2 line is connected to, default: 24
• spiSpeedHz - Speed of the SPI communication in Hz, default: 100000
• txTimeoutMs - Maximum time in milliseconds to wait for a packet transmission to finish, default: 2000

startReceive()

Put the LoRa module in receive mode and enable the receive event.

Returns a Promise that resolves with no value.

stopReceive()

Put the LoRa module in standby mode and stop receiving packets.

Returns a Promise that resolves with no value.

send(payload)

• payload - A Buffer of up to 255 bytes

Send a packet via LoRa.

Returns a Promise that resolves with no value after the transmission is finished.

Note: After transmitting a packet, the module switches into standby mode automatically. If you want to continue receiving packets after a transmission, you will need to call startReceive() after the transmission completed.

getVersion()

Get the chip version number from the module.

Returns a Promise that resolves with the version number (one-byte integer).

---

Events

• receive(packet) - Emitted when a LoRa packet has been received
• receiveError() - Emitted when an invalid LoRa packet has been received

receive(packet)

Event that is emitted when a LoRa packet is received.

packet is an object containing the following properties:

• payload - A Buffer containing the packet contents
• rssiDb - RSSI of the packet in dB
• snrDb - SNR of the packet in dB

receiveError()

Event that is emitted when a LoRa packet is received but was discarded due to receive errors (e.g. CRC check failed).