NeoPixel LED Strip Control

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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 — see PPS conflict note below)
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 "Pin conflict with the GPS HAT" The Uputronics GPS/RTC HAT uses BCM 18 for its PPS signal (see GPS HAT Setup). If your station has the GPS HAT installed, move the NeoPixel data line to another PWM-capable pin (e.g., BCM 12, PWM0 or BCM 13, PWM1) and update the pin in Hardware Settings.

!!! 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

  1. Navigate to Admin → Hardware Settings.
  2. Enable the NeoPixel LED Strip toggle.
  3. Set the GPIO Pin (BCM numbering, default: 18).
  4. Set the Number of LEDs to match your strip length.
  5. Set Brightness (0–255, default: 128).
  6. Enable Flash on Alert to trigger the strip when an EAS alert is received.
  7. Set Flash Interval (ms) — how rapidly the strip flashes during an alert (default: 500ms).
  8. Click Save Settings.
  9. Restart the hardware service:
    sudo systemctl restart eas-station-hardware.target

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 1 Number of LEDs in strip — set to your actual strip length
LED order neopixel_led_order GRB Byte order of the strip: GRB, RGB, GRBW, or RGBW — set via a dropdown in the web UI, not an environment variable
Brightness neopixel_brightness 128 Global brightness (0–255)
Standby color neopixel_standby_color (0, 10, 0) — dim green Shown when no alert is active
Alert color neopixel_alert_color (255, 0, 0) — red Shown during an active EAS alert
Flash on alert neopixel_flash_on_alert true Flash strip during EAS alerts
Flash interval neopixel_flash_interval_ms 500 Flash period in milliseconds

All fields live on the Admin → Hardware Settings → NeoPixel tab; there is no .env equivalent for any of them.

Alert Colors

There is one configurable standby color (shown when idle, default dim green) and one configurable alert color (shown during an active EAS broadcast, default red) — set as color pickers on the NeoPixel settings tab. The strip does not currently map different colors to different alert severities; every active alert uses the same configured alert color.

When Flash on Alert is enabled, the strip flashes between the alert color and off at the configured interval for the duration of the broadcast. After the broadcast completes, the strip returns to its standby 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

rpi-ws281x is already declared in requirements.txt (ARM builds only) and installed automatically by install.sh / update.sh on Raspberry Pi hardware. Only install it manually if you're troubleshooting a missing import outside that normal flow:

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

Permissions

eas-station-gpio.service runs as the unprivileged eas-station user (not root), and does not request CAP_SYS_RAWIO or any other capability. GPIO access goes through /dev/gpiomem, which on Raspberry Pi OS is owned by the gpio group — the service user needs to be a member of it:

sudo usermod -a -G gpio eas-station
sudo systemctl restart eas-station-hardware.target

Check the service user:

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

Testing the LED Strip

There is no dedicated "test strip" action for NeoPixel today. To confirm wiring and software are working without waiting for a live alert:

  • Save the NeoPixel settings on Admin → Hardware Settings — the strip should immediately switch to the configured standby color.
  • Trigger a Required Weekly Test (RWT) broadcast (Broadcast → Weekly Tests → Run Test Now) and confirm the strip switches to the alert color and flashes for the duration.

Troubleshooting

LEDs do not light up

  1. Verify power supply is connected and providing 5V.
  2. Confirm GPIO pin number matches physical wiring (BCM numbering, not board numbering).
  3. Check that eas-station-hardware.target is running:
    sudo systemctl status eas-station-hardware.target
  4. Look for errors in the hardware log:
    journalctl -u eas-station-gpio.service -f

"Can't open /dev/gpiomem" error

The service user needs to be in the gpio group — see Permissions above. Running as root also works but is not required or recommended.

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 a different byte order than the default. Change the LED Order dropdown on Admin → Hardware Settings → NeoPixel to match your strip (GRB — most WS2812B — RGB, GRBW, or RGBW for SK6812 RGBW strips), then save and restart the hardware service.

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.