> For the complete documentation index, see [llms.txt](https://docs.smart-stuff.nl/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.smart-stuff.nl/p1-modbus-dongle/support/faq.md).

# FAQ

<details>

<summary>What do the LEDs on the adapter mean?</summary>

LEDs depend on the hardware implementation. A regular NRGD has a separate blue mono status LED, a green power LED in the P1 input and a P1 output LED. On the ZAP2/NRGDH-based NRGD, the blue status LED is absent and an RGB status LED occupies the former green LED position in the P1 input. This RGB LED uses the same colors and indications as D1MC. See [LED indicators](/p1-modbus-dongle/firmware-v2-current/led-indicators.md) for the detailed firmware v2 behavior.

</details>

<details>

<summary>The power LED is off or unstable</summary>

On a regular NRGD, the green power LED in the P1 input should be on continuously when the adapter has power. The ZAP2/NRGDH-based NRGD has an RGB status LED in this position instead of a separate green power LED. If the adapter appears unpowered or unstable, check the P1 cable, USB power supply and whether the smart meter supplies enough power through its P1 port. See the applicable [hardware page](/p1-modbus-dongle/hardware-variants/hardware-variants.md) for power requirements.

</details>

<details>

<summary>The status LED shows three short flashes followed by a pause</summary>

On firmware v2 this means that the RS485 module is not detected. Modbus communication is disabled until the module is available again. On P1 Modbus Pro, check that the module is installed correctly and reconnect or reboot the adapter.

</details>

<details>

<summary>Which firmware version is installed on the adapter?</summary>

Connect the adapter with a USB data cable and open the [Device Manager](/p1-modbus-dongle/firmware-v2-current/device-manager.md). It shows the hardware type and installed firmware version. For a legacy P1 Modbus adapter that cannot connect to the Device Manager, read the version through its serial port; this is supported from firmware version 1.1.0.

</details>

<details>

<summary>Strange errors</summary>

Always check that the phases are connected correctly. Phase 1 to phase 1 of the smart meter and phase 1 to the consumer appliance, etc. If they are reversed, the control circuit is no longer correct.

</details>