RF69HCW Elixir Interface

Interact with RFM69HCW radio modules via spi.

datasheet

Arduino compatible library

Purchase from adafruit

Purchase from SparkFun

Current Features / Known Issues / wants

• Packet encryption/decryption
• Send packets
• Receive packets
• Auto Ack packets
• Support other frequencies
• AES encryption
• Basic Usage documentation
• RSSI value reading
• Processing packet data outside of the library
• Packet recv/send telemetry (because why not?)
• Unit tests?

WARNINGS

Be sure to check your local laws for legal radio bands.

Compatability

Packets are encoded/decoded with the same format as LowPowerLabs RF69 library version 1.4 (described here). The goal is to have feature parity with the Arduino library.

Wiring

Currently i've only tested on Raspberry Pi, but it should work on any device that ElixirCircuits supports.

Usage

iex()> {:ok, pid} = RF69.start_link [
  reset_pin: 16,
  ss_pin: 25,
  irq_pin: 13,
  spi_bus_name: "spidev0.0",
]
{:ok, #PID<0.1660.0>}
iex()> receive do
...()>  %RF69.Packet{} = packet ->
...()>  IO.inspect(packet, label: "received packet")
...()>  :ok
...()> end
packet received: %RF69.Packet{
  ack_requested?: true,
  is_ack?: false,
  payload: "123 ABCDEFGHIJK",
  rssi: -42,
  sender_id: 2,
  target_id: 1
}
:ok
iex()> RF69.send(pid, 2, "hello node 2 from gateway node!")
:ok
iex()> 

Examples

The API defined is pretty low level. If you want to use it, you should probably wrap the radio server in your own genserver. See the Logger Example for an example.

There is a repo here with some more examples

Acking

By default the rf69 server will respond to acks If your implementation requires user acking, when starting the rf69 server, pass in auto_ack?: false. This will require that in your code when you receive a packet, you will be responsible for acking it in the configured amount of time required by your other nodes. Here's an example:

def handle_info(%Packet{requires_ack?: true} = packet, state) do
  # Process the packet (whatever that means to your application)
  case process_packet(packet) do
    :ok -> 
      # packet processed successfully.
      RF69.ack(state.rf69, packet)
    :error -> 
      # packet processed unsuccessfully.
      # The protocol has no concept of "nack"ing, so the lack of
      # an ack should be considered a "nack"
      Logger.error "Not acking #{inspect(packet)}"
  end
  {:noreply, state}
end

Encryption

AES Encryption is handled at the hardware level. All you as a developer need to do is load the encryption key when starting the server.

WARNING: This key must be EXACTLY 16 bytes wide.

{:ok, pid} = RF69.start_link(encrypt_key: "sampleEncryptKey")