Getting Started¶

Introduction¶

This is a Circuitpython driver library for the nRF24L01(+) transceiver.

Originally this code was a Micropython module written by Damien P. George & Peter Hinch which can still be found here

The Micropython source has since been rewritten to expose all the nRF24L01’s features and for Circuitpython compatible devices (including linux-based SoC computers like the Raspberry Pi). Modified by Brendan Doherty & Rhys Thomas.

• Authors: Damien P. George, Peter Hinch, Rhys Thomas, Brendan Doherty

Features currently supported¶

• Change the address’s length (can be 3 to 5 bytes long)

• Dynamically sized payloads (max 32 bytes each) or statically sized payloads

• Automatic responding acknowledgment (ACK) packets for verifying transmission success

• Append custom payloads to the acknowledgment (ACK) packets for instant bi-directional communication

• Mark a single payload for no acknowledgment (ACK) from the receiving nRF24L01 (see ask_no_ack parameter for send() and write() functions)

• Invoke the “re-use the same payload” feature (for manually re-transmitting failed transmissions that remain in the TX FIFO buffer)

• Multiple payload transmissions with one function call (see documentation on the send() function and try out the Stream example)

• Context manager compatible for easily switching between different radio configurations using The with statement blocks (not available in rf24_lite.py version)

• Configure the interrupt (IRQ) pin to trigger (active low) on received, sent, and/or failed transmissions (these 3 events control 1 IRQ pin). There’s also virtual representations of these interrupt events available (see irq_dr, irq_ds, & irq_df attributes)

• Invoke sleep mode (AKA power down mode) for ultra-low current consumption

• cyclic redundancy checking (CRC) up to 2 bytes long

• Adjust the nRF24L01’s builtin automatic re-transmit feature’s parameters (arc: number of attempts, ard: delay between attempts)

• Adjust the nRF24L01’s frequency channel (2.4 - 2.525 GHz)

• Adjust the nRF24L01’s power amplifier level (0, -6, -12, or -18 dBm)

• Adjust the nRF24L01’s RF data rate (250kbps, 1Mbps, or 2Mbps)

• An nRF24L01 driven by this library can communicate with a nRF24L01 on an Arduino driven by the TMRh20 RF24 library.

• fake BLE module for sending BLE beacon advertisements from the nRF24L01 as outlined by Dmitry Grinberg in his write-up (including C source code).

• Multiceiver^TM mode (up to 6 TX nRF24L01 “talking” to 1 RX nRF24L01 simultaneously). See the Multiceiver Example

• Networking capability that allows up to 781 transceivers to interact with each other.

  • This does not mean the radio can connect to WiFi. The networking implementation is a custom protocol ported from TMRh20’s RF24Network & RF24Mesh libraries.

Dependencies¶

This driver depends on:

• Adafruit CircuitPython Firmware or the Adafruit_Blinka library for Linux SoC boards like Raspberry Pi

• adafruit_bus_device (specifically the SPIDevice class)

  Tip

  Use CircuitPython v6.3.0 or newer because faster SPI execution yields faster transmissions.

• The SpiDev module is a C-extension that executes SPI transactions faster than Adafruit’s PureIO library (a dependency of the Adafruit_Blinka library).

The adafruit_bus_device, Adafruit_Blinka library, and SpiDev libraries are installed automatically on Linux when installing this library.

Installing from PyPI¶

On supported GNU/Linux systems like the Raspberry Pi, you can install the driver locally from PyPI. To install for current user:

pip3 install circuitpython-nrf24l01

To install in a virtual environment in your current project:

mkdir project-name && cd project-name
python3 -m venv .env
source .env/bin/activate
pip3 install circuitpython-nrf24l01

Pinout¶

The nRF24L01 is controlled through SPI so there are 3 pins (SCK, MOSI, & MISO) that can only be connected to their counterparts on the MCU (microcontroller unit). The other 2 essential pins (CE & CSN) can be connected to any digital output pins. Lastly, the only optional GPIO pin on the nRF24L01 is the IRQ (interrupt; a digital output that’s active when low) pin and is only connected to the MCU via a digital input pin during the interrupt example.

Using The Examples¶

See examples for testing certain features of this the library. The examples were developed and tested on both Raspberry Pi and ItsyBitsy M4. Pins have been hard coded in the examples for the corresponding device, so please adjust these accordingly to your circuitpython device if necessary.

For an interactive REPL¶

All examples can be imported from within an interactive python REPL.

1. Make sure the examples are located in the current working directory. On CircuitPython devices, this will be the root directory of the CIRCUITPY drive.

2. Import everything from the desired example. The following code snippet demonstrates running the Simple Test example

   >>> from nrf24l01_simple_test import *
   Which radio is this? Enter '0' or '1'. Defaults to '0'
       nRF24L01 Simple test.
       Run slave() on receiver
       Run master() on transmitter
   >>> master()
   Transmission successful! Time to Transmit: 1563.904 us. Sent: 0.0
   Transmission successful! Time to Transmit: 1804.938 us. Sent: 0.01
   Transmission successful! Time to Transmit: 1690.977 us. Sent: 0.02
   Transmission successful! Time to Transmit: 1674.681 us. Sent: 0.03
   Transmission successful! Time to Transmit: 1729.976 us. Sent: 0.04
   

For CircuitPython devices¶

1. Copy the examples to the root directory of the CIRCUITPY device.

2. Rename the desired example file to main.py.

3. If the REPL is not already running, then the example should start automatically. If the REPL is already running in interactive mode, then press Ctrl+D to do a soft reset, and the example should start automatically.

For CPython in Linux¶

1. Clone the library repository, then navigate to the repository’s example directory.

   git clone https://github.com/2bndy5/CircuitPython_nRF24L01.git
   cd CircuitPython_nRF24L01/examples
   

2. Run the example as a normal python program

   python3 nrf24l01_simple_test.py
   

What to purchase¶

See the following links to Sparkfun or just google “nRF24L01+”.

• 2.4GHz Transceiver IC - nRF24L01+

• SparkFun Transceiver Breakout - nRF24L01+

• SparkFun Transceiver Breakout - nRF24L01+ (RP-SMA)

It is worth noting that you generally want to buy more than 1 as you need 2 for testing – 1 to send & 1 to receive and vise versa. This library has been tested on a cheaply bought 6 pack from Amazon.com, but don’t take Amazon or eBay for granted! There are other wireless transceivers that are NOT compatible with this library. For instance, the esp8266-01 (also sold in packs) is NOT compatible with this library, but looks very similar to the nRF24L01+ and could lead to an accidental purchase.

Power Stability¶

If you’re not using a dedicated 3V regulator to supply power to the nRF24L01, then adding capacitor(s) (100 µF + an optional 0.1µF) in parallel (& as close as possible) to the VCC and GND pins is highly recommended. Stabilizing the power input provides significant performance increases. More finite details about the nRF24L01 are available from the datasheet (referenced here in the documentation as the nRF24L01+ Specification Sheet)

About the nRF24L01+PA+LNA modules¶

You may find variants of the nRF24L01 transceiver that are marketed as “nRF24L01+PA+LNA”. These modules are distinct in the fact that they come with a detachable (SMA-type) antenna. They employ additional circuitry with the antenna for enhanced Power Amplification (PA) and Low Noise Amplification (LNA) features. While they boast greater range with the same functionality, they are subject to a couple lesser known (and lesser advertised) drawbacks:

Additional requirements for the PA/LNA modules¶

These requirements are dependent on what manufacturer produced the radio module.

1. Needs a stronger power source. Below is a chart of advertised current requirements that many MCU boards’ 3V regulators may not be able to provide (after supplying power to internal components).

   Specification	Value
   Emission mode current(peak)	115 mA
   Receive Mode current(peak)	45 mA
   Power-down mode current	4.2 µA

   Important

   These values may be different depending on what manufacturer produced the radio module. Please consult the manufacturer’s specifications or datasheet.

2. Needs shielding from electromagnetic interference. Shielding usually works best when it has a path to ground (GND pin), but this connection to the GND pin is not required.

nRF24L01(+) clones and counterfeits¶

This library does not directly support clones/counterfeits as there is no way for the library to differentiate between an actual nRF24L01+ and a clone/counterfeit. To determine if your purchase is a counterfeit, please contact the retailer you purchased from (also reading this article and its links might help). The most notable clone is the Si24R1. I could not find the Si24R1 datasheet in english. Troubleshooting the SI24R1 may require replacing the onboard antenna with a wire. Furthermore, the Si24R1 has different power amplifier options as noted in the RF_PWR section (bits 0 through 2) of the RF_SETUP register (address 0x06) of the datasheet. While the options’ values differ from those identified by this library’s API, the underlying commands to configure those options are almost identical to the nRF24L01. The Si24R1 is also famous for not supporting auto_ack correctly because the designers “cloned” a typo from the 1^st version of the nRF24L01 (non-plus) datasheet into the Si24R1 firmware. Other known clones include the bk242x (also known as RFM7x).

Contributing¶

Contributions are welcome! Please read our Code of Conduct before contributing to help this project stay welcoming.

Please review our Contributing Guidelines for details on the development workflow.

To initiate a discussion of idea(s), you need only open an issue on the source’s git repository (it doesn’t have to be a bug report).

Future Project Ideas/Additions¶

The following are only ideas; they are not currently supported by this circuitpython library.

• There’s a few blog posts by Nerd Ralph demonstrating how to use the nRF24L01 via 2 or 3 pins (uses custom bitbanging SPI functions and an external circuit involving a resistor and a capacitor)

• TCI/IP OSI layer, maybe something like TMRh20’s RF24Ethernet

Sphinx documentation¶

Please read our Contributing Guidelines for instructions on how to build the documentation.