> 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/hardware-variants/installation.md).

# Installation

Connections, power and physical controls differ by hardware. Use the page for your adapter:

* [D1MC](/p1-modbus-dongle/hardware-variants/hardware-variants/d1mc.md) — DIN-rail hardware with DSMR/P1 and HAN-NVE support, screw-terminal Modbus RTU and flexible 5 V power.
* [P1 Modbus Pro (NRGD)](/p1-modbus-dongle/hardware-variants/hardware-variants/p1-modbus-pro.md) — compact adapter with an RS485 module and P1 output. Includes regular NRGD and ZAP2/NRGDH-based implementations with different `A`/`B` terminal positions; the latter also supports HAN-NVE using a HAN (RJ45)-to-RJ12 cable.

After installing the hardware, use the [Device Manager](/p1-modbus-dongle/firmware-v2-current/device-manager.md) and follow the shared [firmware v2 configuration](/p1-modbus-dongle/firmware-v2-current/configuration.md).

{% hint style="warning" %}
The old white P1 Modbus adapter has a micro-USB connector and a different fixed Modbus terminal pin-out. It has not been sold for years. Do not use its wiring diagram for current hardware; retain existing installation information only when servicing an old unit.
{% endhint %}

## General Modbus RTU checks

* De-energize the installation before changing wiring.
* Match `A` and `B` to the labels and instructions for both devices.
* Use a suitable twisted pair and follow the connected equipment manufacturer's requirements for cable length, topology, grounding and shielding.
* Configure the same device ID, baud rate and serial format on the adapter and Modbus master.
* Apply 120 Ω termination only where required by the RS485 bus topology.