Increasing payload size above 32 bytes using nRF24L01+

Question

I tried to modify the example in the following page, by replacing the given string with a 56 bytes one after making all the suitable changes to read(), write() and max_payload_size(increased to 64 bytes), payload_size() parameters/methods in the RF24 library.

http://shanes.net/another-nrf24l01-sketch-string-sendreceive/

The problem is the receiver truncates the string to 32 characters. Is 32 bytes a hard limitation for payload with the nrf24l01+ radio? If so how to I modify the receiver in above example problem to receive the entire string?

Answer 1

If you look at the specification or datasheet for the nRF24l01+, you will see that the 32 byte payload is the maximum that the device can handle.

For example:

If you need to transmit anything larger than 32 bytes, you will need to develop a protocol that splits up your data into chunks of 32 bytes or less and sends the data in several packets.

The actual protocol you design is up to you, but a simple technique might be using the first packet to send a count of the number of data packets to expect and then simply send those packets, each with a part of your data and reassemble it at the receiving end.

You may need to design something more robust so you don't get confused by lost packets or bad data. The larger your payload, the more chance of transmission errors, so it might be an idea to experiemnt with the payload size to get the best throughput for your particular application.