Linux General/Raspberry Pi

Table of Contents

• Potential PreConfiguration
• Build Options
• Connections and Pin Configuration
  • Linux kernel (SPIDEV driver) and the GPIO chip number
  • General
  • MRAA Constructor
  • SPI_DEV Constructor
  • Pins
• brief history of RF24 library lineage

RF24 supports a variety of Linux based devices via various drivers. Some boards like RPi can utilize multiple methods to drive the GPIO and SPI functionality.

Potential PreConfiguration

If SPI is not already enabled, load it on boot:

sudo raspi-config

1. Update the tool via the menu as required
2. Select Advanced and enable the SPI kernel module
3. Update other software and libraries

   sudo apt-get update
   sudo apt-get upgrade

Build Options

The default build on Raspberry Pi utilizes the included BCM2835 driver from the BCM2835 Library

1. See the Linux section for automated installation.
2. Manual install:

   make
   sudo make install

Connections and Pin Configuration

Using pin 15(GPIO22) for CE, pin 24(GPIO8 commonly labeled as CE0) for CSN

Can use any available SPI BUS for CSN.

In general, use

RF24 radio(<ce_pin>, <a>*10+<b>);

for proper constructor to address the correct spi device at /dev/spidev<a>.<b>

Choose any GPIO output pin for radio CE pin.

Warning

The pin numbers may be different for certain systems. In this library's examples, we use the BCM pin numbers for BroadCom chips such as those used on all Raspberry Pi models.

For Raspberry Pi clones, such as Orange Pi or Banana Pi, defer to the pin numbers described in their corresponding documentation/manual.

Hint: If libgpiod is installed (not required for this library), then you can use the included CLI tools shipped with libgpiod to gleam system-specific details.

Linux kernel (SPIDEV driver) and the GPIO chip number

This RF24 library, as of v1.4.9, uses the Linux kernel's Character Device API to interface with GPIO pins (AKA "lines" in kernel docs). Previous versions used the deprecated "sys fs" interface.

By default, this library attempts to use pins exposed via /dev/gpiochip0. Some systems have multiple public-facing GPIO chips integrated (ie nVidia Jetson series). If your system exposes the desired GPIO pins via a different chip (ie /dev/gpiochip4), then the RF24_LINUX_GPIO_CHIP can be set to the correct value when compiling the library.

cmake .. -DRF24_LINUX_GPIO_CHIP="/dev/gpiochip4"

General

RF24 radio(22, 0);

MRAA Constructor

RF24 radio(15, 0);

See the MRAA documentation for Raspberry Pi support

SPI_DEV Constructor

RF24 radio(22, 0);

See the Raspberry Pi documentation about the GPIO pins

Pins

PIN	NRF24L01	RPI	RPi -P1 Connector
1	GND	rpi-gnd	(25)
2	VCC	rpi-3v3	(17)
3	CE	rpi-gpio22	(15)
4	CSN	rpi-gpio8	(24)
5	SCK	rpi-sclk	(23)
6	MOSI	rpi-mosi	(19)
7	MISO	rpi-miso	(21)
8	IRQ	-	-

brief history of RF24 library lineage

Based on the arduino lib from J. Coliz, the library was berryfied by Purinda Gunasekara then forked from github stanleyseow/RF24 to jscrane/RF24-rpi

Network lib also based on farconada/RF24Network