NeoPixel LED Strip Control

EAS Station supports WS2812B/NeoPixel addressable RGB LED strips for visual alert indication. When an EAS alert is received or broadcast, the LED strip can flash or display color patterns to provide a visible at-a-glance status indicator.

Supported Hardware

Component	Specification
LED type	WS2812B (NeoPixel), SK6812, or compatible
Data signal	Single-wire 5V or 3.3V logic
GPIO pin	Configurable (default: BCM 18, PWM0)
Power	External 5V supply recommended for strips >30 LEDs
Maximum LEDs	Software configurable (tested up to 300)

Physical Wiring

Signal Connection (Raspberry Pi)

LED Strip Wire	Raspberry Pi Connection
Data In (DIN)	GPIO BCM 18 (Pin 12) — recommended
Ground	GND (Pin 6 or any GND pin)
+5V	External 5V supply (do NOT use Pi's 5V for strips >10 LEDs)

!!! warning "Power requirements" Each WS2812B LED draws up to 60mA at full white. A 60-LED strip at full brightness requires ~3.6A at 5V. Always use an external 5V power supply rated for your strip length. Connect the supply's GND to the Raspberry Pi's GND to establish a common ground.

Level Shifting

The Raspberry Pi's GPIO outputs 3.3V logic while WS2812B LEDs expect 5V data signals. In most cases, 3.3V data signals drive WS2812B LEDs reliably, but for longer strips or if you experience data corruption, add a level shifter (e.g., 74AHCT125).

Configuration

Via the Web Interface

Navigate to Admin → Hardware Settings.
Enable the NeoPixel LED Strip toggle.
Set the GPIO Pin (BCM numbering, default: 18).
Set the Number of LEDs to match your strip length.
Set Brightness (0–255, default: 128).
Enable Flash on Alert to trigger the strip when an EAS alert is received.
Set Flash Interval (ms) — how rapidly the strip flashes during an alert (default: 500ms).
Click Save Settings.

Restart the hardware service:

sudo systemctl restart eas-station-hardware

Configuration Fields

Setting	Variable	Default	Description
Enabled	`neopixel_enabled`	`false`	Enable NeoPixel support
GPIO pin	`neopixel_gpio_pin`	`18`	BCM pin number
LED count	`neopixel_num_pixels`	`30`	Number of LEDs in strip
Brightness	`neopixel_brightness`	`128`	Global brightness (0–255)
Flash on alert	`neopixel_flash_on_alert`	`true`	Flash strip during EAS alerts
Flash interval	`neopixel_flash_interval_ms`	`500`	Flash period in milliseconds

Alert Color Mapping

When Flash on Alert is enabled, the LED strip displays colors based on alert severity:

Severity	Color	Description
Extreme	Red (full brightness)	Life-threatening emergency
Severe	Orange	Significant threat
Moderate	Yellow	Moderate hazard
Minor	Blue	Minor hazard
Test (RWT/RMT)	Green	Weekly/monthly test
Unknown	White	Unclassified event

During a broadcast, the strip flashes at the configured interval. After the broadcast completes, the strip returns to its idle state (off, or a dim indicator color).

Software Requirements

NeoPixel control requires the rpi_ws281x (also known as rpi-ws281x-python) library, which in turn requires root-level PWM access or DMA access.

Installing the Library

source /opt/eas-station/venv/bin/activate
pip install rpi_ws281x

Permissions

The rpi_ws281x library requires access to /dev/mem for DMA-based LED control. The eas-station-hardware service must run as root or with the CAP_SYS_RAWIO capability.

Check the service user:

grep User /opt/eas-station/systemd/eas-station-hardware.service

If the service does not run as root, add the capability or add AmbientCapabilities=CAP_SYS_RAWIO to the service unit file.

Testing the LED Strip

From the VFD/hardware control dashboard at /admin/hardware, click Test NeoPixel Strip to cycle through all alert colors. This verifies that wiring and software are working without waiting for a live alert.

Via command line:

sudo python scripts/test_neopixel.py --pin 18 --count 30

Troubleshooting

LEDs do not light up

Verify power supply is connected and providing 5V.
Confirm GPIO pin number matches physical wiring (BCM numbering, not board numbering).

Check that eas-station-hardware is running:

sudo systemctl status eas-station-hardware

Look for errors in the hardware log:
```
journalctl -u eas-station-hardware -f
```

"Can't open /dev/mem" error

The service needs elevated permissions. Run the hardware service as root or grant the CAP_SYS_RAWIO capability.

First LED lights but rest do not

Check the data wire connection at the strip's DIN end.
Confirm you have a common GND between the Pi and the external power supply.
Try reducing brightness — high currents can cause voltage drop.

Colors look wrong (e.g., green and red are swapped)

Some LED strips use GRB color order instead of RGB. Adjust the color order in the hardware settings:

NEOPIXEL_COLOR_ORDER=GRB

LEDs flicker randomly

Usually caused by insufficient power supply current or a missing common ground between the Pi and the power supply. Add decoupling capacitors (470µF, 25V) across the power supply leads near the strip.

rpi_ws281x not available error

The library is only available on Raspberry Pi hardware. On non-Pi systems, NeoPixel support is disabled automatically. Check whether rpi_ws281x imported successfully:

python -c "import rpi_ws281x; print('OK')"

Integration with Tower Lights

EAS Station also supports industrial-grade tower lights (e.g., Patlite or similar serial-controlled units) via a separate hardware integration. Tower lights and NeoPixel strips can be used simultaneously. See Admin → Hardware Settings → Tower Light for tower light configuration.

Back to Documentation Index

This document is served from docs/hardware/NEOPIXEL_LED_CONTROL.md in the EAS Station installation.