emonHP - Heat Pump Monitoring

As of Aug 2026 emonHP2 hardware is not yet released

Introduction

emonHP V2 is a system for monitoring heat pump operation. It is designed to work with OpenEnergyMonitor, but can be used as a standalone system.

The system provides the following interfaces:

• MBUS
• RS485
• DHW, pulse, and OneWire (DS218B20 temperature) inputs
• USB-C power
• 40-pin Raspberry Pi header
• OLED I2C display
• RFM69CW RF transceiver

The board uses a STM32C031K6U microcontroller

Getting started

Getting a board

• Purchase a heat pump monitoring system from the OpenEnergyMonitor Shop
• Build your own!
  • With KiCad installed, run ./generate.py in the pcb directory (tested on Linux and macOS only) to generate manufacturing files (KiCad PCB, Gerbers, BoM).

emonHP2

Note

Setting up as an integrated emonHP system requires a Raspberry Pi 4 or 5. These expose extra UART ports on the 40-pin header which are not available on older versions.

Connect the Raspberry Pi to the 40 pin header.

Warning

Power must only be applied to one of the emonHP's USB-C port or the Raspberry Pi's power port, never both.

Connections

• DHW Status: Signal 1 input - GPIO27 - Pin 13
• Pulse: Signal 2 input - GPIO22 - Pin15 - soft-pull down enabled (NOT TESTED)
• OneWire (DS18B20 ) - Signal 3 input - GPIO0*

* Set dtoverlay=w1-gpio,gpiopin=0 in /boot/firmware/config.txt to support OneWire on GPIO0

• Push button - GPIO17 - pin11: set push_btn = Button(17, pull_up=True, bounce_time=0.1, hold_time=5) in emonPiLCD2.py

Firmware & Rasi Setup

See firmware repo: https://github.com/openenergymonitor/emonhp-rs