Wiznet makers

Overview

OpenAmber is open-source firmware that replaces the factory Windows CE controller inside an Itho Daalderop Amber heat pump with an ESP32 running ESPHome. Built by the maker behind the GitHub project Jordi1990/openamber, it turns a closed, screen-bound heat pump controller into a fully observable and controllable device inside Home Assistant, the popular open-source home automation platform. The heat pump's inside and outside units speak Modbus over an RS485 serial bus; OpenAmber reads and writes those registers directly, exposing temperatures, pump states, compressor frequency, alarms, and control modes as normal Home Assistant entities.

For the build that uses a Waveshare ESP32-P4 board, networking is handled by a WIZnet W5500 Ethernet controller over SPI. Because that board has no built-in wireless radio, the W5500 is what carries the controller's data to and from Home Assistant over a wired LAN, which is the more reliable choice for a device bolted into a heating system that people depend on year round.

What problem it solves

A stock Amber heat pump is a sealed appliance: the controller is a fixed unit, the logic is not user-accessible, and integration with a smart home is limited. OpenAmber opens that up. By physically moving the Modbus wires from the original controller to an ESP32 with an RS485 interface, the firmware takes over control of the pump and gives the owner direct, transparent access to the machine's behaviour.

Key terms for a first-time reader: Modbus over RS485 is a simple, robust industrial serial protocol used to read and write numbered registers on a device. ESPHome is a framework that turns YAML configuration into firmware for ESP32-class microcontrollers and connects them to Home Assistant with almost no coding. A W5500 is a wired Ethernet controller chip that gives a microcontroller a standard RJ45 network connection.

What it can do

OpenAmber reproduces and extends the original controller's behaviour, including domestic hot water and three-way valve control, heating and cooling, full PWM control of the P0 circulation pump with optional PID control on the heating delta-T, compressor frequency modulation via a PID controller, configurable maximum-power modes, two-stage frost protection similar to the original software, a software thermostat, a five-point heat curve, backup heater and hybrid external backup heater support, a post-defrost boost using the backup heater, error-code sensors, external thermostat inputs for heating and cooling, and SG-Ready smart-grid support. The project documents the full Modbus register map for both the inside unit and the outside unit, which is what makes this level of control possible.

Hardware and the WIZnet role

The firmware runs on any ESP32 with an RS485 board, and the project calls out two off-the-shelf paths. The preferred build uses a Waveshare ESP32-S3 Touch LCD 5 inch board, chosen because it offers a touchscreen, RS485, and a 24 V input so it can reuse the same cabling that powered the original controller. A second, screen-less option uses a dedicated Itho Daalderop Amber control module sold by a third-party shop.

Separately, the project ships an ESP32-P4 build whose configuration brings up networking with a WIZnet W5500 over SPI. On that board the W5500 provides the wired Ethernet link the P4 needs to reach Home Assistant, which matters for a controller that should stay connected without depending on Wi-Fi signal quality near a heat pump.

Where it fits and who it is for

OpenAmber is aimed at owners of an Itho Daalderop Amber heat pump who want full local control and deep visibility inside Home Assistant, and who are comfortable moving a pair of Modbus wires and flashing ESPHome firmware. It sits in the growing family of ESPHome projects that replace or augment closed appliance controllers, and it is a good reference for anyone building a Modbus-to-Home-Assistant bridge that also needs a dependable wired network link.

Value and limits

The value is control and transparency: an owner gets the original functions back plus PID-based tuning, smart-grid readiness, and full telemetry, all local and open source. The limits are honest ones. The project is community firmware that requires physically rewiring the heat pump's Modbus connection, so it is for confident makers rather than a plug-in accessory, and some features remain on the roadmap, including buffer-tank support, richer error handling, and OpenTherm thermostat support. The WIZnet W5500 appears specifically in the ESP32-P4 build as the wired-network option.

FAQ

What is OpenAmber? Open-source ESPHome firmware that replaces the Windows CE controller in an Itho Daalderop Amber heat pump with an ESP32, exposing full control and telemetry in Home Assistant over Modbus RS485.

Where does the WIZnet W5500 come in? In the Waveshare ESP32-P4 build, the W5500 provides wired Ethernet so the controller reaches Home Assistant over a LAN instead of Wi-Fi. That board has no built-in radio, so the W5500 is its network path.

Do I need to modify my heat pump? Yes. You move the A and B Modbus wires from the original controller to the ESP32's RS485 port, and on the touchscreen build you reuse the original 24 V, GND, and FG lines for power.

Is this a finished commercial product? No. It is active open-source firmware with a documented Modbus register map and a public roadmap, intended for makers comfortable with wiring and flashing.