urf_lib VS uECG

Of significant stuff I wrote an nRF52 "core" (not Arduino core, it's for using with arm-gcc and makefiles) with necessary functions to feel comfortable there: https://github.com/ultimaterobotics/urf_lib - apart from simpler stuff like timers, uart, radio handlers and star protocol, I also made a custom implementation of BLE peripheral device (4.2-ish, hadn't implemented everything from 4.2, only parts I needed - that indeed was terribly complicated, if Nordic had their softdevice open sourced, I wouldn't do that). Since then I've added there fast ADC, PWM, SPI with DMA, persistent storage parts but those are not yet published.

You may want to check the library I made some time ago: https://github.com/ultimaterobotics/urf_lib (radio related stuff is in urf_radio.c, .h files)- I hadn't implemented there methods with external setting of length and packet ID (both are intended to be handled outside of the library) - but if something doesn't work as intended in your case, you can trace an example of sending from nRF52 to nRF24 here https://github.com/ultimaterobotics/uMyo_v2 , in file main.c preparation of the packet is handled with prepare_data_packet32(), which is later sent via a single call of rf_send(data_packet, data_packet[1])

I in fact wrote a library for nrf52 family that, among other things, handles my own RF protocol (https://github.com/ultimaterobotics/urf_lib although no documentation yet) - I'm using star architecture, one central node talking to multiple peripherals at close to realtime schedule - communication cycle time is <2 ms per connected device, variable payload up to 250 useful bytes, no in-built acks or retransmits. That's because I had the need for such pattern in multiple projects I worked on.

But overall that still would be a very simplistic version. You can check my code for uECG device: https://github.com/ultimaterobotics/uECG/blob/main/uECG_v5/ecg_processor.c - function r_detector_step, I've put a significant effort into it and it can work with _much_ noisier signal than what you have in your setup :) But it takes some pages of code...

You can check our uECG project - it's open source, main code is located here https://github.com/ultimaterobotics/uECG (and there are several links to other our repositories for radio library, bootloader and other stuff). It is a single channel ECG.