Simplest possible way to send/receive 3 bytes with nRF24L01+

[fabio_leitao]

Hi dear friends from Nordic Semi, I´m in great trouble trying to make these nRF24L01+ to work, one unit as a transmiter, and one unit as a receiver, it can be to send 3 bytes at a time. I once used the Italian Telecontrolli RXQ-2 modules, but it´s not more available on the market. So, the best,cheapest available product is yours. But, to get started with it is really difficult. I want to send three bytes at a time, and from many Internet posts about the product, and after studying your datasheet, I have found that i need to set up the modules like that :

For setting up the transmitter module:

• CE low -Wait 10 microseconds

• CSN low

• Wait 10 microseconds

• Send SPI 0b00100000

• Send SPI 0b00001110

• CSN high

• Wait 10 microseconds ; Configures the unit for TX_prime

• CSN low

• Wait 10 microseconds

• Send SPI 0x31

• Send SPI 0x3

• CSN high

• Wait 10 microseconds ; Configures pipe0 buffer size to 3 bytes

• CSN low

• Send SPI 0b11100001

• CSN high ; Flush TX

• Wait 10 microseconds

• CSN low

• Send SPI 0b11100010

• CSN high ; Flush RX

• Wait 2 miliseconds

CE high

For the transmitting routine:

• CE low

• Wait 10 microseconds

• CSN high

• Wait 10 microseconds

• CSN low

• Wait 10 microseconds

• Send SPI 0xa0

• Send SPI 3 bytes

• Wait 10 microseconds

• CSN high

• CE high

• Wait 10 milliseconds

• CE low

• Wait 10 microseconds

• Return to main routine.

For setting up the receiver module:

• CE low

• Wait 10 microseconds

• CSN low

• Wait 10 microseconds

• Send SPI 0b00100000

• Send SPI 0b00001111

• CSN high

• Wait 10 microseconds ; Configures the unit for RX_prime

• CSN low

• Wait 10 microseconds

• Send SPI 0x31

• Send SPI 0x3

• CSN high

• Wait 10 microseconds ; Configures pipe0 buffer size to 3 bytes

• CSN low

• Send SPI 0b11100001

• CSN high ; Flush TX

• Wait 10 microseconds

• CSN low

• Send SPI 0b11100010

• CSN high ; Flush RX

• Wait 2 miliseconds CE high

For the receiving routine:

• CE low

• Wait 10 microseconds

• CSN low

• Wait 10 microseconds

• Send SPI 0x27

• Send SPI 0x70 ; Clean status

• CSN high

• Wait 10 microseconds

• CE low

• Send SPI 0x61

• Send SPI 0xFF - Get from SPI byte 1

• Send SPI 0xFF - Get from SPI byte 2

• Send SPI 0xFF - Get from SPI byte 3

• CSN high

• Wait 10 microseconds

• CE high

• Wait 10 microseconds -Back to the main routine

Both units are adequately wired, and in close distance one to other. I am using PIC16F877, running at 4 MHz, and programming in Assembler. I consider the channel settings the reset default, and I think it does not need to be changed to make things just work. What else should I do to make these things work ? What are the SPI settings that I should use ? Is there any other command or routine that I should implement to get the stuff working ? Thank you very much in advance.

Fabio Leitao Rio de Janeiro, Brazil

• Wait 10 microseconds
• Return to main routine.

[mnhs]

I am slightly missing the initialization part. Or maybe I just can't see it. Basically, you need to initialize both modules before any communication. I have found one of my experiments with nRF24L01 chips (it works but there can be mistakes, it was not thoroughly tested ... and yeah, it is not commented - but you can easily follow the commands using datasheet). I am posting it as a image to keep the formatting right.

Initialization of TX:

Transmit of 32 bytes payload stored in "buffer":

Initialization of RX:

Unfortunately I can't provide you with "tutorial" code for receive because it is wrapped in my original software and thus a bit difficult to read, but basically you need to read STATUS register periodically and check for bit 6 (RX_DR). Then, you can read the RX FIFO - it is really easy, similar to transmit.

This is only "somehow-it-works" example. I was testing the range and performance with it and I needed to glue the parts of code as quickly as possible, in an hour or so. You will need to study the datasheet and adapt your code to your application.