Scrambled console on RPi3

[bob prohaska]

On Wed, Feb 21, 2018 at 10:11:30AM -0800, Rodney W. Grimes wrote:
> > A few minutes ago I unplugged and replugged a PL2303 serial adapter in an
> > RPi3 running r329495. The serial console announced the disconnection with
> > ugen0.4: <vendor 0x067b product 0x2303> at usbus0 (disconnected)
> > uplcom0: at uhub1, port 2, addr 4 (disconnected)
> > uplcom0: detached
> > 
> > followed by  a torrent of unprintable garbage. Then it calmly announced
> > 
> > <vendor 0x067b product 0x2303> at usbus0
> > uplcom0 on uhub1
> > uplcom0: <vendor 0x067b product 0x2303, class 0/0, rev 1.10/4.00, addr 4> on usbus0
> > 
> > The displaying host is a Pi3 running the latest Raspbian. It's not clear
> > how much, if any, of the oddity is an artifact of the display. Experience
> > to date suggests none.
> >  
> > Far as I can tell the pl2303 and the host RPi3 are working normally. I've 
> > never done this experiment before on a Pi3, but have done it many times on
> > a Pi2 and nothing of the sort has happened.
> > 
> > Hope this is of interest to someone...
> 
> Do you have which 4 wires connected?
> Gnd - should be connected
> TX - should be connected
> RX - should be connected
> Vcc - Do not connect this wire, doing so can lead to odd behavior
>       unless you happen to be powering the device this way, and
>       in your case, the RPi3 has a higher load current than USB
>       can normally supply.


Yes, the wiring was correct, working before & after and untouched 
during the incident. 

For clarity, the USB-side connect/disconnect and scrambled console were 
on the Pi3. The "client" serial connection was to a Pi2 console which
seemed, and after several hours remains, unperturbed.


The console of the Pi3 was being viewed on a Raspbian Pi3 wirelessly
connected by ssh to a Pi2, which used a second pl2303 to monitor the 
Pi3 console in a cu session. The latter two  hosts are running -current,
both are prone to dropping ssh connections when loaded and the pl2303
is prone to lockups as noted elsewhere on this list. The unplug/replug 
cycle was done to unstick the pl2303 in the Pi3.

For the moment I'm tempted to think it's a USB problem, which could 
affect both ethernet and usb serial adapters. 

Thanks for reading!

bob prohaska