MultiNav Pro+ BLE - channel selection behavior at long range, any control over it?

@Monica Randall yeah this is a genuinely good question and you're thinking about it the right way. BLE's adaptive frequency hopping does its job well in crowded urban RF environments, but at extreme range the tradeoff flips — you're less worried about interference avoidance and more worried about link margin on each individual hop, so consistently landing on a noisy channel at 5km is a much bigger deal than it would be at 50 meters.

 

The STM32WB07 that powers the MultiNav Pro+ does expose some channel map configuration at the HCI/LL level — you can technically define a channel map that marks specific channels as unused, which effectively steers the hopper away from known bad channels at your site. The GitHub repo is public so you can dig into the firmware directly: https://github.com/RFOXiA/MultiNav-Pro-Long-Range-BLE-Module-Firmware-STM32WB07 — that's probably your fastest path to seeing what's currently exposed versus what would need to be added.

 

That said, full channel locking (picking one channel and staying there) isn't standard BLE behavior and would mean stepping outside the spec in ways that could affect the FCC certification, so I'd be cautious there. Channel map restriction to a curated subset of the cleaner channels is the more practical middle ground and stays within spec. Worth raising directly with Moamen if you want to push on this — the firmware is actively developed and this is exactly the kind of edge-case use requirement that tends to get prioritized when someone has a concrete deployment scenario behind it.

Honestly the MultiNav Pro+ doesn't expose direct channel locking through the standard API as far as I've ever found - BLE AFH is pretty much handled at the controller level and the module doesn't give you a hook into the channel map in any documented way. That said, some people have had luck using the HCI vendor-specific commands if your host stack allows it, though that's very much "here be dragons" territory and I wouldn't count on it being consistent across firmware versions. If channel-level control is a real requirement for your use case you might be better off looking at whether the underlying radio supports a proprietary mode, because fighting AFH at long range through the standard BLE stack is kind of a losing battle.

Melinda's right on the HCI vendor-specific route, and just to add - if you can get your hands on the firmware changelog for whatever version you're on, a few releases back there was a quiet addition to the vendor command set that lets you set a channel map hint, not a hard lock but the controller does seem to weight it at least somewhat. No idea if it survived into the latest builds tbh, worth checking before you go down the proprietary mode rabbit hole.

Worth trying the channel map hint Omar mentioned but honestly at genuine long range the bigger lever I've found is just backing off the TX power slightly and letting the link settle - counterintuitive but aggressive TX at the edge tends to make the controller's channel scoring go haywire and you end up hopping worse not better. If you have a spectrum analyzer anywhere near the deployment site, even a cheap RTL-SDR pass, figure out which 2.4GHz segments are actually clean before you mess with channel weighting at all, otherwise you're tuning blind.