PoE Control

The Interceptor PoE Board is managed through the /proc/pse interface, which provides control over individual PoE ports.

The /proc/pse Interface

The PoE ports are controlled via a simple text-based interface at /proc/pse.

Checking Port Status

cat /proc/pse

Example output:

Board 0:
  Port 0: power on (15.2W)
  Port 1: disabled
  Port 2: power on (8.7W)
  Port 3: searching
  Port 4: disabled
  Port 5: power on (12.1W)
  Port 6: searching
  Port 7: disabled

Port Status Values

Controlling Ports

Enable a Port

echo "enable-port <board> <port>" > /proc/pse

Examples:

# Enable port 0 on board 0
echo "enable-port 0 0" > /proc/pse

# Enable port 5 on board 0
echo "enable-port 0 5" > /proc/pse

# Enable port 2 on board 1 (second PoE board)
echo "enable-port 1 2" > /proc/pse

Disable a Port

echo "disable-port <board> <port>" > /proc/pse

Examples:

# Disable port 3 on board 0
echo "disable-port 0 3" > /proc/pse

# Disable port 7 on board 1
echo "disable-port 1 7" > /proc/pse

Reset a Port

Power-cycle a port (disable then re-enable):

echo "reset-port <board> <port>" > /proc/pse

Example:

# Reset port 2 on board 0
echo "reset-port 0 2" > /proc/pse

Set PoE Mode (AF vs AT)

By default, ports are configured for 802.3at (PoE+, 30W). To limit a port to 802.3af (15W), use:

echo "set-af-mode <board> <port>" > /proc/pse

Example:

# Set port 2 on board 0 to AF mode (15W max)
echo "set-af-mode 0 2" > /proc/pse

Board and Port Numbering

Single PoE Board Configuration

Dual PoE Board Configuration

Common Operations

Enable All Ports on Board 0

for port in 0 1 2 3 4 5 6 7; do
  echo "enable-port 0 $port" > /proc/pse
done

Disable All Ports on Board 0

for port in 0 1 2 3 4 5 6 7; do
  echo "disable-port 0 $port" > /proc/pse
done

Check Power Consumption

cat /proc/pse | grep "power on"

Monitor Status in Real-Time

watch -n 1 'cat /proc/pse'

Important Notes

ip link vs /proc/pse

The ip link set command controls the network interface, not the PoE power.

# This controls the network link, NOT the PoE power
ip link set poe0 up    # ❌ Does not enable PoE power
ip link set poe0 down  # ❌ Does not disable PoE power

# Use /proc/pse to control PoE power
echo "enable-port 0 0" > /proc/pse   # ✅ Enables PoE power
echo "disable-port 0 0" > /proc/pse  # ✅ Disables PoE power

Power Budget Management

The system does not automatically manage power budget. If you enable more ports than your PSU can handle, you may experience:

• Voltage drops
• Port resets
• System instability

Calculate your power budget before enabling ports:

Fault Recovery

If a port enters fault status:

1. Check for short circuits or damaged cables
2. Verify the connected device is PoE-compatible
3. Reset the port:

   echo "reset-port 0 <port>" > /proc/pse
   

Scripting Examples

Startup Script to Enable Specific Ports

Create /usr/local/bin/poe-init.sh:

#!/bin/bash
# Enable PoE ports on boot

# Ports to enable on board 0
ENABLED_PORTS="0 1 2 5"

for port in $ENABLED_PORTS; do
  echo "enable-port 0 $port" > /proc/pse
  sleep 0.5
done

echo "PoE ports initialized"

Make executable and add to startup:

chmod +x /usr/local/bin/poe-init.sh
# Add to /etc/rc.local or create a systemd service

Port Status Check Script

#!/bin/bash
# Check PoE port status

echo "=== PoE Port Status ==="
cat /proc/pse

echo ""
echo "=== Active Ports ==="
cat /proc/pse | grep "power on" | wc -l
echo "ports delivering power"

echo ""
echo "=== Total Power ==="
cat /proc/pse | grep -oP '\d+\.\d+W' | awk '{sum += $1} END {print sum "W total"}'

Troubleshooting

“Permission denied” Error

You need root privileges to write to /proc/pse:

sudo echo "enable-port 0 0" > /proc/pse   # ❌ Won't work

# Use this instead:
echo "enable-port 0 0" | sudo tee /proc/pse

# Or run as root:
sudo -i
echo "enable-port 0 0" > /proc/pse

Port Won’t Enable

1. Check if /proc/pse exists (OS version requirement)
2. Verify board is connected (FFC cable)
3. Check 48V power is connected
4. Look for error messages in dmesg:

   dmesg | grep -i poe
   

Device Not Receiving Power

1. Verify port shows “power on” in /proc/pse
2. Check device is PoE-capable
3. Try a different cable
4. Try a different port
5. Check total power budget

API Reference

Commands

Parameters

Note for Cruiser Board Users

Last modified December 30, 2025