NRF24L01P.md

NRF24L01+ Wireless Module

• KEYWORDS: Module,NRF,NRF24L01,NRF24L01P,NRF24L01+,Wireless,Radio,Transceiver

The Nordic NRF24L01+ transceiver is very popular and works well with Espruino. It is sold in very inexpensive wireless modules that interface via SPI. They can easily be obtained via eBay and many other places for prices as low as $2.

A driver for it is available in the [[NRF24L01P.js]] module.

Connect as follows:

NRF24L01+	Name	Espruino Original	Type
1	GND	GND	GND
2	3.3V	3.3	3.3v
3	CE	B1	GPIO Out
4	CSN	B0	GPIO Out
5	SCK	A5	SPI SCK
6	MOSI	A7	SPI MOSI
7	MISO	A6	SPI MISO
8	IRQ	unused	GPIO In

Note: These pins are suggested for the Original Espruino Board as they are in the middle, leaving the edges free for IO. However you can use any GPIO pins you want (with software [[SPI]] you needn't use SPI pins either).

For the [[Pico]] there is an adaptor shim available as part of the shim collection that makes the NRF24 a lot easier to solder!

We'd also suggest that you add a 10nF - 100nF decoupling capacitor between GND and 3.3v. Some cheaper modules can be unrelible without this.

You can either connect the module with wires and mount it separately, or you can solder it into the prototype area, and run wires as follows on the back of the board. We'd recommend using thin, solid core wire for this.

The finished wiring might look like this:

Notes

• The NRF24L01+ is a packet radio. It can transmit and receive small packets (up to 32 bytes) of data
• Devices have a transmit and a receive address
• Devices can only transmit or receive. They can't do both at the same time
• Transmits are acknowledged - a module knows if the data it sent was received
• The NRF24 module can be unreliable at the higher

The Espruino module allows you to send and receive strings. It does this by sending enough packets to contain the string plus a terminating zero. It will retry, but it is possible for parts of the string to get missed out.

Simple Usage

We've made simple handlers that allow you to send commands, receive data, and even reprogram a device...

Just do the following for a Slave:

SPI1.setup({sck:A5, miso:A6, mosi:A7});
var nrf = require("NRF24L01P").connect( SPI1, B0, B1 );
function onInit() {
  nrf.init([0,0,0,0,1], [0,0,0,0,2]);
}
onInit();
setInterval(function() {
  nrf.slaveHandler();
}, 50);

And the following for a Master:

SPI1.setup({sck:A5, miso:A6, mosi:A7});
var nrf = require("NRF24L01P").connect( SPI1, B0, B1 );
function onInit() {
  nrf.init([0,0,0,0,2], [0,0,0,0,1]);
}
onInit();
setInterval(function() {
  nrf.masterHandler();
}, 50);

Note the two addresses that are given to init - one is the transmit address, one is a receive address. We also use the onInit function, which is called automatically by Espruino when it starts up.

On a Master all you have to do is use nrf.sendCommand to send a command to the Slave Espruino, and in a few milliseconds the result will appear:

nrf.sendCommand("1+2", function(r) { print("=="+r); });
=3

nrf.sendCommand("analogRead(A0)", function(r) { print("=="+r); });
=0.356694

nrf.sendCommand("LED2.set()", function(r) { print("=="+r); });
=undefined

You can even reprogram the Espruino wirelessly!

nrf.sendCommand("function on() { LED3.set(); }");
nrf.sendCommand("on();");

To communicate with another Espruino, all you need to do to is to call nrf.setTXAddr([1,2,3,4,5]) on the master, giving the address that you have to the Slave Espruino's nrf.init function.

Advanced Usage

The usage of slaveHandler and masterHandler is not required - if you want, you can call methods such as send and getDataPipe() directly. For instance you could make a simple wireless sensor:

SPI1.setup({sck:A5, miso:A6, mosi:A7});
var nrf = require("NRF24L01P").connect( SPI1, B0, B1 );
function onInit() {
  nrf.init([0,0,0,0,1], [0,0,0,0,2]);
}
onInit();
setInterval(function() {
  var value = analogRead(A0); // read a value in
  nrf.sendString(""+value);
}, 5000);

And then a receiver:

SPI1.setup({sck:A5, miso:A6, mosi:A7});
var nrf = require("NRF24L01P").connect( SPI1, B0, B1 );
function onInit() {
  nrf.init([0,0,0,0,2], [0,0,0,0,1]);
}
onInit();

dataLine = "";
setInterval(function() {
  while (nrf.getDataPipe() !== undefined) {
    var data = nrf.getData();
    for (var i in data) {
      var ch = data[i];
      if (ch===0 && dataLine!=="") {
        console.log(dataLine);
        // we could even save it onto an SD card using require('fs').appendFile("log.txt", dataLine+"\n");
        dataLine = "";
      } else if (ch!==0) {
        dataLine += String.fromCharCode(ch);
      }
    }
  }
}, 50);

More Advanced Usage

You can send individual packets using NRF.send(data), where data is an array of numbers of length NRF.PAYLOAD. To receive you can use the same NRF.getData() function. For more information consult the module ([[NRF24L01P.js]]).

Reference

• APPEND_JSDOC: NRF24L01P.js

Using

• APPEND_USES: NRF24L01+

Buying

NRF24L01+ modules are usually based on Nordic's own reference design, so can be purchased from many places:

• eBay
• digitalmeans.co.uk