Ble_2Mbit vs Nrf_2Mbit radio mode... what are the practical differences?

[Andrew Fernandes]

We are looking at developing a proprietary protocol using the nRF52832/40 and were interested in the specific and practical differences between the Ble_2Mbit vs Nrf_2Mbit radio modes.

From the product specification documents, I know that the Nrf_2Mbit mode has a one-byte preamble (versus the Ble_2Mbit two-byte preamble). From searching the Nordic forums, there was mention that the modulation index is "different" between the two.

Can Nordic provide any sort of guidance as to what the observed, practical difference between the two radio modes would be? Differences in bit error rates? Intermodulation distortion? Radio set-up AGC reliability... (yes, I'm reaching here... RF design is not my expertise at all...)  :-)

And before it is mentioned, we have looked - extensively - at ESB and Gazelle, and neither match our requirements.

Any info would be much appreciated!

[haakonsh]

For all intents and purposes the two modes are very similar, so much so that the only practical difference you need to know is that the 2mbps BLE mode receiver has 4dB higher sensitivity than the nRF mode, and can be used with that advantage for proprietary protocols as well. See Receiver operation. 

You said you looked at ESB and gazell and that they do not match your requirements, what exactly are your requirements? I might be able to help you further with that knowledge. 

[Andrew Fernandes]

Thank you for the quick reply, haakonsh, great to know, and much appreciated!

I might take you up later on your kind offer of help, but right now we're very much in the experimental stage.

Basically, for brief intervals we require very high transfer rates, but may not be able to turn the radios around between TX and RX modes reliably given timing requirements.

So what looks like it may work is frequency hopping every millisecond or so, and transmitting the packet 2-3 times with some FEC codes thrown in.

That seems to get our bit error rates and dropped/corrupted frame rate down to acceptable errors.

BTW - just wanted to call out Nordic with some sincere thanks for the quality of their docs, SDKs, and this online forum. I have been working with other companies whose idea of a spec sheet could have been written by a five year old and with support that is nonexistent for sub-$100k customers. So Nordic's efforts are much appreciated!