XIAO BLE Sense: More with nrf24L01+ communication

 XIAO BLE Sense: More with nrf24L01+ communication

Emulating the Enhanced Shock-Burst Protocol

So its been a little while since I received a BLE Sense board based on the NRF52840 from https://www.seeedstudio.com/ and man oh man it has taken up a lot of my time. This is one of my favorite hobbies, so creating a library for ESB communication with nrf24 modules has been quite a lot of fun!

The radio works with logical pipes and defined radio addresses, just like the NRF24L01 and interaction with it is not as complicated as it could be. Getting the ESB protocol working has been a bit tougher than I originally thought it would be though.

As shown in the image above, pipe or logical address 0 can have a unique address, but pipes 1 through 7 must share a base address, very similar to the 24l01.

It seems that the radio must be disabled when switching between TX and RX states, it took me a while to figure this out programmatically, until I noticed this in the datasheet. 

Interestingly enough, the new, enhanced RF52840 does not implement any internal protocols, ESB must be entirely handled via software.

I have my nrf_to_nrf radio driver up and working now with many radio features. It allows users to use the API from the RF24 library to interact with the radio. I am having problems getting static payloads to transfer correctly, but simply enabling the dynamic payload feature enables the RF24 examples to function correctly, and it works with the rest of the RF24 communication stack, the different layers will need to be updated to accept the new library.

The nrf_to_nrf library only has a single-layer buffer at the moment, but it shouldn't be too difficult to implement a 3 layer FIFO like the nrf24s have. It would be helpful if I could drive the radio via IRQs but so far I haven't had any luck with IRQ handling. My cohort in RF24 programming is working on an alternative layer that uses code from the NRF52 SDK, but we might need to have IRQ handling running for that to be a viable option. We will see, the NRF24Network and higher layers have had adjustments made to allow the new library to work. Users can manually install from source until a new release is made to the libraries, which will update via the Arduino Library Manager.

Thanks again to Seeed Studio for sending me this device, new hardware is always fun to play with!