This is the Arduino NRF24 library. It provides an object-oriented interface for sending and receiving data messages with Nordic nRF24L01 based radio modules, such as the sparkfun WRL-00691 http://www.sparkfun.com/products/691
The nRF24L01 (http://www.sparkfun.com/datasheets/Wireless/Nordic/nRF24L01P_Product_Specification_1_0.pdf) is a low-cost 2.4GHz ISM transceiver module. It supports a number of channel frequencies in the 2.4GHz band and a range of data rates.
This library provides functions for sending and receiving messages of up to 32 octets on any frequency supported by the nRF24L01, at a selected data rate.
Up to 2 nRF24L01 modules can be connected to an Arduino, permitting the construction of translators and frequency changers, etc.
This library provides classes for
Example Arduino programs are included to show the main modes of use.
The version of the package that this documentation refers to can be downloaded from http://www.airspayce.com/mikem/arduino/NRF24/NRF24-1.12.zip You can find the latest version at http://www.airspayce.com/mikem/arduino/NRF24
You can also find online help and disussion at http://groups.google.com/group/NRF24-arduino Please use that group for all questions and discussions on this topic. Do not contact the author directly, unless it is to discuss commercial licensing.
Tested on Arduino Diecimila, Duemilanove and Mega with arduino 1.0 on OpenSuSE 12.1 with avr-libc-1.7.1-1.1, cross-avr-binutils-2.19.1-33.1 and cross-avr-gcc-4.3.3_20100125-28.1, and with arduino-0021 on the same platforms
All messages sent and received by this NRF24 library must conform to this packet format, as specified by the nRF24L01 product specificaiton:
The physical connection between the nRF24L01 and the Arduino require 3.3V, the 3 x SPI pins (SCK, SDI, SDO), a Chip Enable pin and a Slave Select pin. If you are using the Sparkfun WRL-00691 module, it has a voltage regulator on board and can be run with 5V VCC The examples below assume the Sparkfun WRL-00691 module
Connect the nRF24L01 to most Arduino's like this (Caution, Arduino Mega has different pins for SPI, see below),
For an Arduino Leonardo (the SPI pins do not come out on the Digital pins as for normal Arduino, but only appear on the ICSP header)
For an Arduino Mega:
and you can then use the default constructor NRF24(). You can override the default settings for the CSN and CE pins in the NRF24() constructor if you wish to connect the slave select CSN to other than the normal one for your Arduino (D10 for Diecimila, Uno etc and D53 for Mega)
Caution: on some Arduinos such as the Mega 2560, if you set the slave select pin to be other than the usual SS pin (D53 on Mega 2560), you may need to set the usual SS pin to be an output to force the Arduino into SPI master mode.
Caution: this module has not been proved to work with Leonardo, at least without level shifters between the NRF24 and the Leonardo. Tests seem to indicate that such level shifters would be required with Leonardo to make it work.
It is possible to have 2 radios conected to one arduino, provided each radio has its own CSN and CE line (SCK, SDI and SDO are common to both radios)
The following example programs are provided: -nrf24_ping_client, nrf24_pin_server. This is a matched pair. The client sends (acknowledged) 4 byte timestamp to the server which replies (acknowledged). The client measures the round-trip time and prints it. Typical RTT is 1-2 msec. These are compatible radio wise with the ping_client and ping_server programs that come with the Mirf library though the electrical connections are different -nrf24_specan. Example sketch showing how to create a primitive spectrum analyser with the NRF24 class. The nRF24L01 received power detector is only one bit, but this will show which channels have more than -64dBm present. -nrf24_audio_tx, nrf24_audio_rx. This is a matched pair. The clinet sends a stream of audio samples measured from analog input 0 to the receiver, which reconstructs them on output D6. See comments in those files for electrical requirements. The pair demonstrates the use of NRF24 in NOACK modefor improved performance (but no reliability). Can achieve 6.4kHz sample rate. Dont expect good quality audio!
The performance of this radio seems to be very good. I was able to build ping client/server that was able to achieve over 800 round trips per second (at 0dBm power, 2Mbps, channel 1, 4 byte payload each way, 1 checksum byte) when the radios were next to each other. This rate could still be achieved at 15m distance, but the orientation of the radios and obstructions became critical. The human body can easily block these signals. Best response was when the chip antennas were broadside to each other.
It is possible to get even better streaming performance using NOACK mode (see the nrf24_audio_tx sample) at the cost of nop reliability. In NOACK mode, at 2Mbps, 32 byte payload, can get about 1900 packets per second: 60800 bytes of payload per second
Frequency accuracy may be debatable. For nominal frequency of 2401.000 MHz (ie channel 1), my Yaesu VR-5000 receiver indicated the center frequency for my test radios was 2401.121 MHz. Its not clear to me if the Yaesu is the source of the error, but I tend to believe it, which would make the nRF24l01 frequency out by 121kHz.
The radio is enabled all the time, and switched between TX and RX modes depending on whether there is any data to send. Sending data sets the radio to TX mode. After data is sent, the radion automatically returns to Standby II mode. Calling waitAvailable() or waitAvailableTimeout() starts the radio in RX mode.
The radio is configured by default to Channel 2, 2Mbps, 0dBm power, 5 bytes address, payload width 1, CRC enabled 1 byte CRC, Auto-Ack mode. Enhanced shockburst is used. P1 is the receive pipe. P0 is set to the transmit address to enable autoack.
Memory usage of this program is minimal. The compiled ping client and server programs are about 4000 bytes. RAM requirements of the library are minimal.
Install in the usual way: unzip the distribution zip file to the libraries sub-folder of your sketchbook.
This software is Copyright (C) 2012 Mike McCauley. Use is subject to license conditions. The main licensing options available are GPL V2 or Commercial:
This is the appropriate option if you want to share the source code of your application with everyone you distribute it to, and you also want to give them the right to share who uses it. If you wish to use this software under Open Source Licensing, you must contribute all your source code to the open source community in accordance with the GPL Version 2 when your application is distributed. See http://www.gnu.org/copyleft/gpl.html
This is the appropriate option if you are creating proprietary applications and you are not prepared to distribute and share the source code of your application. Contact info@.firstname.lastname@example.org@m.payce.nosp@m..com for details.