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PoE switch control (poe_switch_control.py)

scripts/switch/poe_switch_control.py manages PoE power on individual ports of the TP-Link SG2016P managed switch. It is the backend used by PDUDaemon to power OpenWrt One (port 1) and LibreRouter 1 (port 2) — devices that receive power over Ethernet rather than via the Arduino relay board.

1. PoE port map

Ports 1–8 on the SG2016P support PoE. Only ports in active use:

Switch port DUT Power mode Notes
1 OpenWrt One PoE (802.3at) Native PoE — direct
2 LibreRouter 1 PoE via 48 V→12 V splitter Active-to-passive conversion; see switch config

2. Usage

# Turn PoE on/off for a single port
poe_switch_control.py on  1
poe_switch_control.py off 1

# Power-cycle (off → sleep → on, default delay 3 s)
poe_switch_control.py cycle 1
poe_switch_control.py cycle 1 --delay 5

# Multiple ports at once
poe_switch_control.py on 1 2

3. Authentication

The script uses SwitchClient from labgrid-switch-abstraction for SSH. Credentials are loaded in order:

  1. SWITCH_PASSWORD environment variable
  2. ~/.config/switch.conf (INI format):
[switch]
host     = 192.168.0.1
user     = admin
password = <your-password>

The switch does not accept SSH public keys; password auth is required. See switch config for the SSH alias setup.

4. Lock serialization

Multiple PDUDaemon workers or manual invocations can run concurrently. The script uses fcntl.flock on /tmp/switch.lock to serialize SSH sessions and prevent contention on the switch's SSH daemon (which handles only one session at a time reliably).

5. PDUDaemon integration

The Ansible role configures PDUDaemon with a localcmdline driver:

[poe-switch]
driver  = localcmdline
cmd_on  = poe_switch_control.py on %s
cmd_off = poe_switch_control.py off %s
cmd_status = poe_switch_control.py status %s

Labgrid target files reference this PDUDaemon entry via the PDUDaemonPower resource:

resources:
  PDUDaemonPower:
    host: localhost
    pdu: poe-switch
    index: 1    # switch port number

6. Troubleshooting

Symptom Likely cause Fix
Authentication failed Wrong password Check SWITCH_PASSWORD or ~/.config/switch.conf
Connection refused Switch SSH not enabled or wrong IP Verify ssh switch-fcefyn works manually
Invalid PoE port Port number > 8 or non-integer Only ports 1–8 support PoE on SG2016P
PoE on command succeeds but DUT stays off Splitter issue (port 2 / LibreRouter) Check 48 V→12 V splitter connection
Lock timeout Another process holding /tmp/switch.lock rm /tmp/switch.lock if the process is gone

See also