Scanning? about bluepy

[IanHarvey]

As mentioned in issues #70 and issues #81, scanning is now implemented! There are no docs yet, and you still have to be root (or fiddle with /dev/hciXX permissions yourselves).

Cheers
IH

[IanHarvey]

So, the issues that come to mind are -

1. The scan results turn up asynchronously over a period of time (e.g. a couple of a minutes), so you'd need to choose a Pythonic way of presenting this. Options include.

• a call which blocks while it scans, and sends results to a callback object (simple, but blocking is kinda antisocial in many situations)
• a call which starts a thread to deliver scan results to some callback object in the background (except threads are always harder than they look)
• fit it into the asyncio framework (but then it's Python-3 only, not simple for simple things, and dictates the whole structure of your program)

2. I need to figure out why 'hcitool lescan' requires root - this seems unreasonable to me. It can probably be fixed with setting permissions on /dev/something appropriately - more research needed.

[oleiman]

Hey Ian,

I've had the opportunity to work on this a bit over the last week. I have a
very simple blocking scanner class in place that scans for a predetermined
period and generates a list of BLE device addresses. Still requires root
access to configure the scan, still not totally sure why.

I basically just pasted the (slightly modified) source for the hcitool
lescan into bluepy-helper.c, sending data back over stdout in the normal
way. The timeout is a little bit hacky, but that scanner loop needs to exit
somehow, otherwise I can't exit the bluepy-helper gracefully. I
guess the whole scan could happen asynchronously in the helper; sounds like
a pain, but might be worth doing.

I doubt this is something worth pushing upstream, but it might be a good
jumping off point. I need this stuff for some demos we're spinning up, so
I'll be poking at it intermittently. Any feedback would be great.

https://github.com/nio-blocks/bluepy/tree/feature/discovery

Thanks,
Oren

EDIT: typo and email response garbage

[IanHarvey]

Sorry for being slow - I should have some time to look at it this week.

Thanks
Ian

[OrenLederman]

Any updates on lescan? Can be very useful

[pcborenstein]

Why does lescan require sudo permission? You must have found a way around it already because you can't connect to a bluetooth device without scanning and finding it.

I've noticed the gatttool can connect to a device without sudo, but hcitool lecc does require sudo. Why is this? I assume answering the first question answers the second too...

[ShuffleBox]

If I remember correctly, if you add your user to the lp group, you should be able to. (Edit for clarity: should be able to access the bluetooth device in that manner. I'm not sure about the implementation of scanning with bluepy)
I didn't look to find the reason it's wired up to that group, but that was the solution when I was accessing a bluetooth adaptor as a regular user on Raspbian (raspberry pi2). Worth a shot.