[arm-allstar] One of two USB URIs dropping off

[David McGough]

Hi Randy,

Okay, yes, looking at the dmesg output, this issue looks power related,
one way or another. Note below that just after the "under voltage"
warning, and before the "voltage normalized," the URI(s) aren't happy.

The micro-USB power connection on the RPi3b+ may be the problem. Another
factor that we've noticed recently is that some brands of the epoxy potted 
5V3A DC-DC converters don't perform as well as others. Frustrating.

A subtle ground loop, even with the hardware in same chassis, might be the
culprit, too.

73, David KB4FXC



On Fri, 11 Jan 2019, Randy Neals wrote:

> Hi David,
> Thanks for the email...
> 
> Usually just one URI stops. It seems to be the first port, my VHF repeater.
> Earlier it seemed like it was alternating with no pattern between repeaters.
> (Thus I wasn't suspecting a bad URI)
> 
> No reboot of the system, no hang. Other repeater usually continues to
> operate.
> 
> The repeaters are ICOM FR-5000/FR-6000
> Both repeater RF modules are in the same metal Icom rack chassis, ie: same
> ground for both repeaters.
> The Audio and COR/PTT come out on DB25 connector on back of repeater.
> 1' cable with signal/audio to URI
> 
> The repeaters are powered from 12VDC power distribution.
> 12V power is from a large communications power supply (Switch mode N+1
> redundant) with battery backup.
> 
> The 5V Pi power is a DC to DC converter rated at 3 Amps. 12V from the same
> distribution as repeater. 5V on micro USB to Pi.
> At first I had a different PS, and swapped early thinking that was the
> problem.
> 
> The Pi is in an aluminum chassis with a tiny fan.
> It is on a rack shelf above the repeater. The Pi chassis is not grounded,
> but it has 2 USB cable, and the power supply cable to the DC DC converter
> which may have ground.
> 
> Here's dmesg
> I see several "under voltage" messages. That doesn't seem good.
> 
> I rebooted just a few minutes ago. When the URI stops again, I'll run dmesg
> again.
> 
> 
> [    7.215868] sd 0:0:0:0: [sda] Assuming drive cache: write through
> 
> [    7.222428]  sda: sda1
> 
> [    7.227933] sd 0:0:0:0: [sda] Attached SCSI removable disk
> 
> [    8.300598] smsc95xx 1-1.1:1.0 eth0: link up, 100Mbps, full-duplex, lpa
> 0xD1E1
> 
> [   13.608033] *Under-voltage detected! (0x00050005)*
> 
> [   17.229524] retire_capture_urb*: 119 callbacks suppressed*
> 
> [   21.938034] Voltage normalised (0x00000000)
> 
> [   26.348512] retire_capture_urb*: 18 callbacks suppressed*
> 
<snip>