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From: <bp@www.zefox.net>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: bookworm wifi (was spontaneous locale change on bookworm)
Date: Sun, 22 Sep 2024 17:12:08 -0000 (UTC)
Organization: A noiseless patient Spider
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The Natural Philosopher <tnp@invalid.invalid> wrote:
> On 22/09/2024 00:53, bp@www.zefox.net wrote:
>> [subject updated to reflect recent observations]
>> 
>> The Natural Philosopher <tnp@invalid.invalid> wrote:
>>>
>>> Well it may be completely irrelevant Bob, but my Pi Zero 2 W issues seem
>>> to have been solved by use of a bigger power supply.
>>> It may be that the wifi chip is the most sensitive to inadequate voltages.
>> 
>> The wifi dropout has repeated three or four times since the initial case.
>> Usually it dropped after an hour or so of uptime and couldn't reconnect
>> on its own, the Pi had to be rebooted. Haven't seen anything more about
>> rfkill after the first incident.
>>   
>> I put a voltmeter on the GPIO power pins, it looks steady at 5.09-5.10 volts.
>> The meter isn't what I'd call a precision unit, but it's likely within 50 mV,
>> so the voltage isn't obviously wrong.
>> 
> 
> Mmm. if you have a scope, also check for noise.
> 

I do have a 'scope, but learned something new in the meantime.

Overnight the connection dropped and would not reconnect. Watching
wavemon showed cyclic behavior, trying 5 GHz, then 2.4 GHz, then
giving up over several attempts. Opening the "edit connection"
settings showed device to be blank. When I set it to wlan0 and
hit "save" the connection immediately came up. 

Wlan0 is the only possibility on this Pi: there's no cable conneted,
so how the device setting could matter, if in fact it did, is unclear. 

There are quite a few competing access points in the neighborhood, 
but mine is still the closest and, usually, the strongest. However, 
it's limited to 2.4 GHz only. Wavemon shows considerable time spent
trying to establish a 5 GHz connecting before falling back to 2.4.
 
Perhaps this is some kind of negotiating failure. I'm using a preset
ssid with password, so there's no question of which AP to negotiate
with. I haven't set DHCP to use a reserved MAC address simply because
the Pi generally gets the same address anyway and I seldom run any
services on this Pi that require access from the LAN. 

Is there some way to force the Pi to not bother attempting a 5 GHz
connection?

Thanks for reading,

bob prohaska




>> Just a few minutes ago the WiFi dropped, then came back up on its own a
>> couple or three minutes later. Wasn't watching the voltmeter, unfortunately.
>> I'll keep an eye peeled more carefully, perhaps it can be caught in the act.
>> 
> That is the sort of behaviour an 'on the edge' wifi subsystem displays.
> 
> My router has 'connection time' and 'reconnection time' set to 1 hour 
> and 1 day.
> 
> I think that after the reconnection time is up, it wants a re-send of 
> the secret keys.
> 
> That is, you will, by design, get disconnected every so often,. The 
> issue is whether the reconnect succeeds.
> 
> Low voltage and/or local noise seem to be issues for the wifi chips in use.
> 
> 
> 
>> Thanks for writing,
>> 
>> bob prohaska
>> 
>> 
>