LED indicators

LED behaviour and diagnostics for firmware v2 hardware variants.

The available LEDs depend on the hardware variant. Firmware v2 uses the status LED for operating state and diagnostics. Separate power and P1 output LEDs, when present, have a fixed hardware function.

Hardware variant	LEDs
Older white dongle	Mono status LED and mono power LED on the P1 input.
NRGD	Mono status LED, mono power LED on the P1 input and mono P1 output LED.
ZAP2	RGB status LED on the input side and mono P1 output LED.
D1MC	Status LED only.

Power LED

The power LED is on when the dongle has power. During normal operation this LED should stay on continuously. If the power LED is off or unstable, check the P1 cable, USB power or smart meter power supply.

P1 output LED

The P1 output LED indicates outgoing P1 data. It blinks when the dongle transmits data on the P1 output.

Status LED

On hardware with an RGB status LED, the color indicates the current state. The brightness can be changed in the Device Manager. On hardware with a mono status LED, the same state is shown without color.

Firmware v1 does not use the RGB status LED behaviour described here. For v1 installations, the status LED is mono.

State	RGB status LED	Mono status LED	Meaning
Startup	Soft white breathing	Soft breathing	The dongle is booting. This normally lasts about 3 seconds.
Ready	Solid blue	On	The dongle is running normally and ready.
Smart meter telegram received	Short green flash	Short blink	A valid smart meter telegram has been received successfully.
Read, parse or Modbus request error	Red pulse	Two short flashes	The dongle detected an error.
RS485 module missing	Three short red flashes, followed by a pause	Three short flashes, followed by a pause	The RS485 module is not detected. Modbus communication is disabled until the module is available again.

Button feedback

When the button is pressed, hardware with an RGB status LED temporarily shows the button action:

Button action	RGB LED indication	Result
Short press	Green while the button is pressed	Reboot the dongle.
Press and hold for more than 5 seconds	Green at first, then red after 5 seconds	Restore factory settings and reboot.