I still don't understand why people are still bothering to use NRF24l01...it's old tech nowadays . Well I get that it's cheaper and bla, bla but when it comes to performance and tuning things up it gets harder imho. Not to forget that you still need another MCU in order to make it work thus increasing BOM and complexity (yes, yes I know why some prefer "decoupled" systems, but still...)
Why not use NRF52832 which is a much more compact solution and let's face it more efficient than the old NRF24L01. Oh and let's not forget that it has a MCU inside also.
I think the list of advantages is obvious:
- More TX power: 4dbm compared to 0dbm.
- Incorporated MCU
- Incorporated DC-DC converter which when enabled will reduce the current consumption in both TX and RX mode (7.5mA in TX mode and 5.4mA in RX mode - this is only for the radio subsystem)
Simplified design when using an already available module like the CDEBYTE or CDSNET from Aliexpress (just search for nrf52832 cdebyte or cdsnet) is also a plus. Those modules are really cheap now - around 3$. Oh and it needs to have those external components (inductors, caps) to be able to use the internal DC-DC converter - the CDEBYTE or CDSNET modules have it.
Now back to this topic main discussion regarding battery powered nodes which need to be pretty responsive no? Well it's not that easy using MySensors to accomplish this - I may be wrong but I tried this for one of my projects and no matter what techniques I used I couldn't achieve the desired results.
Why? Because MySensors it's not designed to create responsive battery powered nodes - please do correct me here @mfalkvidd if I'm wrong. By responsive I mean to make it respond in a time window of <= 1s.
@iancu If designing pretty responsive and battery powered nodes then Bluetooth LE is your best bet. I know that it's not MySensors but only BLE can achieve that as far as I know (NRF52832 supports BLE also which is yet another advantage).
I know that this deviates from MySensors and it's not that have something with this project - it's a really great project but we have to know its limitations (as of now at least).
Another alternative would be LORA modules which this project supports also and which have lower RX current because this is the state you would want to stay in most of the time (NRF52832 has it pretty low with the internal DC-DC enabled). But I'm not familiar with LORA modules and from what I've read the TX time cand get very high depending on the modulation speed which is not ideal also.
So what do we need in the end for MySensors: radio modules with very low RX current and fast TX time. Do they exist? I'm not quite sure to be honest (excluding lots of marketing stuff). Faster TX time means also a faster modulation speed/scheme which is achievable even by NRF24l01 so I don't think this is an issue nowadays.
When it comes to MySensors I think a good start is the NRF52832 based modules at least but it won't guarantee the responsiveness that you're looking for @iancu - for that you need a better software stack and radio protocols also imho.