SX1280 FLRC Initial Work

[jlpoltrack]

Motivation: FLRC offers a lot more throughput at similar sensitivities to LoRa SF5 (currently used for 50 Hz)

Example:

• 0.65 Mb/s, Code Rate 1/2
• Sensitivity: -104 dBm (-105 dBM for LoRa SF5)
• OTA: 2.48 ms
• 100 Hz possible ? : 6,400 Bytes Uplink, 8,200 Bytes Downlink

[jlpoltrack]

Very ugly proof of concept working (repurposes 50 Hz mode for FLRC): https://github.com/jlpoltrack/mLRS/tree/FLRC-Proof-of-Concept

[olliw42]

VERY COOL

I am unfortunately so much behind with so much mLRS stuff that I may not find time myself to test it.

But I think we should get serious about getting this PR merged :)

On a quick glance, I only have one thought: You do have put the label FLRC in each addition (except in one enum, where you want to change it to SX1280_FLRC_xxx), which is great, but I still find it a bit mixed. I'm not sure what to propose instead, but I guess I would have tried how it looks like if one always puts the FLRC in front, like as if it were a class or struct. Which makes me think if the functions couldnt in fact be in a class FLRC inside the sx class? Not very mature thoughts, but this is what crosed my mind. :)

Also, maybe, one could separate by e.g. moving all FLRC stuff to the end, with a nice comment as title "FLRC"

So, it's really just about making it nice, not functional :):):)

[olliw42]

with OTA 2.8 ms, why 100 Hz and not 150 Hz (as I think you suggested initially)?

[jlpoltrack]

On a quick glance, I only have one thought: You do have put the label FLRC in each addition (except in one enum, where you want to change it to SX1280_FLRC_xxx), which is great, but I still find it a bit mixed. I'm not sure what to propose instead, but I guess I would have tried how it looks like if one always puts the FLRC in front, like as if it were a class or struct. Which makes me think if the functions couldnt in fact be in a class FLRC inside the sx class? Not very mature thoughts, but this is what crosed my mind. :)

Also, maybe, one could separate by e.g. moving all FLRC stuff to the end, with a nice comment as title "FLRC"

Many thanks for the feedback (and no rush :) ). For the moment, I've updated the sync word registers and preamble defines to include FLRC so that everything that should use FLRC has 'FLRC' in the name. Have also put everything at the end in FLRC sections.

with OTA 2.8 ms, why 100 Hz and not 150 Hz (as I think you suggested initially)?

When I did some calculations, it seemed that ~2.1 ms per packet was needed for processing. For example, for LoRa 50 Hz:

(7.892 + 2.1) * 2 * 50 = 999.2 ms.

So while the OTA is now 1/3rd of 50 Hz, the processing time doesn't scale down and 100 Hz seemed to fit.

Further, when I did some testing by editing these lines for 100 Hz (or even 53 Hz): https://github.com/olliw42/mLRS/blob/main/mLRS/Common/setup.h#L310 and updating the TOA here: https://github.com/olliw42/mLRS/blob/main/mLRS/Common/sx-drivers/sx128x_driver.h#L238 I couldn't get good results (so I imagine I'm missing something...)

The last test I did was to increase the packet size to 127 bytes (FLRC max) and that had no issues running at 50 Hz, saw over 5 kbytes/sec on the Mission Planner stats screen during a parameter download.

[olliw42]

100 Hz:
ah, ok. Many thx for the insight. 150 Hz would have just sounded "cooler" LOL (also becasue it is what crossfire offers, doesn't it). We will work out the best combination with time.
It's a great start, however.

Hopefully we can get the other two issues (tx crash, rc signals) sorted out.

[olliw42]

merging this.
MANY THX!!!