openwrt ONE: not getting enough PoE power

Michael Richardson mcr at sandelman.ca
Fri Mar 14 20:54:15 PDT 2025


I brought an OpenWRT One to IETF122 Hackathon.

I plugged the 2.5Gb/s port into the IETF hackathon network, and the switch
apparently has PoE (which I didn't care about).  I hooked up the rest of the cables,
including the USB power, but didn't turn it on yet.  I was surprised when I
opened the console that the system was running.... kinda.

With the cable in the PoE port, the device was in a reboot cycle.  Getting to
just before the console shell starts, and then restarting.  I can post a log
if that's useful to someone.
I guess because there wasn't enough amperage on the PoE port.  I unpluged,
turned on the USB adapter and things were fine... so I reconnected the PoE cable, and
the system crashed... back to reboot cycle!  Oh.  That's bad.

I "solved" the problem by inserting a my non-PoE switch in between.
I could have also swapped ports, it now occured to me.

I'm just mentioning this for the benefit for someone searching!

I suppose this is a hardware problem, and probably not solveable.
Maybe I could cut a trace, or maybe there is a zero-ohm resister I could
unsolder to disable PoE.

Maybe fixable in Two: prefer USB power if it's present.
But of course, when I started, it wasn't present, as I wanted the system to
be off until I was ready: I wanted to finish getting serial console alive
before I powered on.

The switch in question:

LLDP neighbors:
-------------------------------------------------------------------------------
Interface:    enxd43a650cda24, via: LLDP, RID: 2, Time: 0 day, 00:25:46
  Chassis:
    ChassisID:    mac cc:98:91:86:53:80
    SysName:      sw-128.meeting.ietf.org
    SysDescr:     Cisco IOS Software, C3560CX Software (C3560CX-UNIVERSALK9-M), Version 15.2(7)E11, RELEASE SOFTWARE (fc3)
                  Technical Support: http://www.cisco.com/techsupport
                  Copyright (c) 1986-2024 by Cisco Systems, Inc.
                  Compiled Fri 23-Aug-24 13:34 by mcpre

--
]               Never tell me the odds!                 | ipv6 mesh networks [
]   Michael Richardson, Sandelman Software Works        | network architect  [
]     mcr at sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [

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