SOLVED! - Pi 2 Wifi problems with a Nexus 7

[Paul_Sengupta]

Got a strange problem. I just tried to configure my Pi 2 with the 20160511 software, or at least the software which I downloaded today. Having written the SD card and allowed the Pi to do its thing, I tried to connect using my 2012 Nexus 7...however it wouldn't. It sees the SSID, tries to connect but can't. So I tried another SD card with some older software in the Pi 2, and that worked fine, I could connect. I tried the "faulty" software in a Pi B+ and I could connect to that too. The only combination which didn't work was the new software and the Pi 2. So I tried to connect another tablet and that worked. I tried rebooting the Nexus but that didn't help. I tried forgetting the network and re-connecting, but that didn't help either. The Nexus is the tablet I use in the air so it would be nice to get this working!

What has changed in software versions which means my Nexus can't connect if it's on a Pi 2? Indeed has something changed?

[Admin]

Hi Paul

I dont have access to a nexus 7.
What I could do is give you access to a number of builds to perform a 'binary chop', then we could isolate the change which appears to break the nexus ?

I would not be able to do this till Monday

Thx
Lee

[Paul_Sengupta]

Ah, great, thanks. I've managed to get it to connect now using battery power on both devices, but the connection is very unreliable and Sky Demon keeps saying that the connection has been lost.

The Asus 173 remains connected with no apparent problems.

[Keithvinning]

Ah, great, thanks. I've managed to get it to connect now using battery power on both devices, but the connection is very unreliable and Sky Demon keeps saying that the connection has been lost.

The Asus 173 remains connected with no apparent problems.

Hi Paul
If you are now using battery on both devices what were you using before

Regards

Keith

[Paul_Sengupta]

I had the Pi plugged into a PI 2 PSU from RS and the tablet plugged into a mains charger.

[JCurtis]

Have both tablets been associated with multiple access points?

From memory Lee had turned the power down on the WiFi dongle, so is your tablet flitting between the PilotAware AP and another one it has been associated to previously? Depending on OS devices will simply use the one from the list of previously associated APs with the best signal.  Easy test is to leave the tablet sitting near the PilotAware and see if it still happens?

[Paul_Sengupta]

Yes, both tablets have multiple saved Wifi access points, but here at home only the home Wifi and the PAWs.

Anyway, this power reduction thing had occurred to me, and it appears there may be a power mismatch somewhere between transmit and receive. I've been experimenting. 

It is possible to get the Nexus to connect but it has to be at the correct distance from the Pi. On battery, this is no closer than about a metre and a half from the Pi, and no further than maybe 3 metres. On mains (Pi RS PSU), this is no closer than about 2 metres and no further than half way down the stairs, whatever that is including attenuations due to house bits, I don't have enough clear space in the house to test the free air range! 

The software I used that worked I marked as being 2016-03-07 which was before the power reduction? I'm writing a new card with that software now so I can put in the licence to experiment with it.

[Paul_Sengupta]

Yep, 2016-03-07 works fine at all ranges. Even downstairs as it has more power...  But more importantly it works with the tablet right up near the Pi.

Edit: Actually, there is a limit, but it works up to about 10cm away, and reliably from about 15cm away which is good enough! 2m away as in the case of 2016-05-11 isn't so good when in the cockpit!

[JCurtis]

That's looks like software then. I was referring to aeons ago during the beta, Lee had the power of the WiFi right down but turned it up a bit to fix dropout issues. No idea about the current releases.

I really must get round to getting hold of a current setup. So far I've used a borrowed one to test against my chargers (work great) and do some basic testing.

[SteveN]

A useful thread.  I have just retrieved a serviceable wifi dongle from my dustbin  that I had assumed gone duff as its range had drastically reduced. Didn't know PAW was running Wifi at low power with latest SW.

[Paul_Sengupta]

I tried again with the new software and it seems to become reliable over a distance of around 1.2 to 1.3 metres, estimated by eye.

[exfirepro]

Hi Guys,

As you say Steve, very interesting. I'm just about to head down to the airfield (main PAW is in the plane). Currently running my iPad mini because I prefer the 4:3 screen ratio for SD, but have still got previously used Nexus 7, so will power it up and give it a try.

Thanks for the heads up Paul.

Best Regards

Peter

[Paul_Sengupta]

Note that this is the 2012 Nexus 7, I didn't try it with my 2013 version. I didn't try distances with the Asus 173 but it seemed to work at a distance of 30-50cm.

[Admin]

Hi Paul
One thing I did change in a recent release was the output power on WiFi it was dropped from 100mw to 50mw. Also the wifi channel was fixed at 9, whereas it is configured based upon the last character in the MAC address.
I wonder if one of these could be affecting you ?

At some point I plan to make these configurable on the web interface
Power, channel, ssid, password
Thx
Lee

[Vic]

Hi All

It was my first running attempt of anything to do with PAW yesterday having just received a wireless adaptor. I too was using a Nexus 7 2012 and was experiencing the same issues as Paul. When looking at the list of available wireless stations prior to attempting the connect, the Pilotaware WAP kept appearing (with good power) then disappearing completely for a second or two. On an unsuccessful attempt to connect, it wouldn't even attempt again until I 'forgot' the PAW and re tried to connect (though still unsuccessfully).

I used 'WiFi Analyser' app on my phone to have a look at what was going on in the spectrum and it showed the PAW on channel 9, the highest signal on the screen but occasionally dropping away to nothing. Significantly,my home access point is on channel 10. I switched off my home wifi briefly and managed to get the N7 connected and it stayed connected even with the home WiFi back up.

I was wondering if the dropping of the PAW signal was some form of auto channel selection trying to kick in but being prevented by the PAW software until something manages to connect to it?

This is , of course, all probably not too important in 'real world' flying use as the PAW is most likely to be the only WAP inside the aircraft