Monitor and control your Daikin system via the room controller (P1/P2) interface!

Daikin (hybrid) heat pump systems are usually controlled by a room thermostat (and/or other controller) over a 2-wire interface, called P1/P2. This project enables to monitor (and, for some systems, control) your Daikin system from e.g. Home Assistant over MQTT via the P1/P2 thermostat wires, using the hard- and software of this project. For monitoring it is only eavesdropping on the regular communication between the main controller and the heat pump. For some models it provides control by acting as an "auxiliary controller" to the main thermostat, requesting the main controller to set certain system parameters on the Daikin system. Depending on your model it may be possible to switch the heat pump or DHW boiler on or off, switch between heating or cooling, set target temperatures, etcetera.

If this project is useful for you, or valuable (I hope you can improve your system's SCOP and reduce your energy bills and CO2 emissions), you may contact me for purchasing a P1P2-ESP-interface, or to share your experiences and log files, or to buy me a coffee. It helps to bring functionality to other models.

New design: P1P2-ESP-interface v1.1

Shown is the new P1P2-ESP-interface v1.1 (more pictures here), a complete single-PCB bus-powered wireless P1P2-MQTT bridge. It is based on an ESP8266 (running P1P2-bridge-esp8266), an ATmega328P (running P1P2Monitor), and the MAX22088 HBS adapter (mounted on the lower side of the PCB). No Arduino or power supply is needed any more. Power is supplied by a DC/DC converter to minimize bus load (30-40mA at 15V). Connect it to P1/P2 near your main controller or near your Daikin system, enter your wifi and mqtt credentials via its built-in AP, and the system runs. Functionality: - monitor and (for some models) control the Daikin heat pump via the P1/P2 bus from Home Assistant (automatic configuration, using MQTT discovery), - communicate via MQTT over WiFi, - accessible via telnet, - OTA upgradable (both ESP and ATmega) (and if that would fail, using an ESP01-programmer via an ESP01-compatible connector), - powered entirely by the P1/P2 bus, no external power supply is needed, low power consumption (only 30-40mA or 0.5W from the P1/P2 bus) thanks to a DC/DC converter, - 4 LEDS for power (white), reading (green), writing (blue), or to signal an error (red), - monitors P1/P2 DC bus voltage, - screw terminals for P1 and P2 wires, - SPI interface option for W5500 ethernet adapter (using an enclosure extension), and - fits nicely in a small semi-transparant enclosure (50mm x 35mm x 20mm without ethernet, or 82mm x 35mm x 29mm with ethernet adapter).

With communication over MQTT, integration with Home Assistand will be(come) automatic, and interfacing to other systems (grafana, OpenHab, EmonCMS) should not be too much work.

By default, the interface only observes and attempts to interpret bus traffic. For some E-series models, especially hybrid models, it may also act as auxiliary controller and control parameter settings over MQTT. FDY(Q) systems are also supported.

How can you build or buy one?

Buy new complete stand-alone P1P2-ESP-interface): I have a number of factory-assembled PCBs (with ATmega328P and ESP12F, bus-powered, with enclosure, soldered, pre-programmed, documented and tested) available(2nd version, shown above, v1.1, October 2022). Please let me know if you are interested: my e-mail address can be found on line 3 of P1P2Serial.cpp.

Buy P1P2-adapter (older design described below): I also sell the original MM1192/XL1192-based 0.5"x2" P1P2-adapter which is a HAT for the Arduino Uno.

Build P1P2-adapter yourself (MM1192/XL1192): schematics and pictures for the MM1192/XL1192-based P1P2-adapter (for use with the Arduino Uno) are here. The MM1192 is available in traditional DIP format so you can build it on a breadboard.

Build P1P2-adapter (MAX22088): Alternatively, you may build a circuit based on the newer MAX22088 IC from Maxim. Be warned that it is difficult to solder: it's only available as a 4x4mm 0.5mm pitch TQFN-24 package. The MAX22088 is powered directly from the P1/P2 bus (take care - we don't know how much power Daikin's P1/P2 bus may provide, perhaps max 60mA) and is able to power the Arduino Uno (max 70mA at Vcc=5V). PCB and schematic files for a MAX22088-based design are made available by Nicholas Roth. His design does not provide galvanic isolation from the P1P2 bus, but that is OK if you connect only via WiFi or ethernet.

Older design: P1P2-adapter

The previous design is the P1P2-adapter this project started with (schema and pictures in https://github.com/Arnold-n/P1P2Serial/tree/main/circuits), a PCB ("HAT") for use on an Arduino Uno. It is based on the MM1192/XL1192 HBS adapter chip. A newer pin-compatible HAT based on the MAX22088 is also available (but not yet documented here).

It is a 0.5" x 2" PCB for the Arduino Uno, and connects to Arduino Uno's GND, 5V, and to digital pins 8 (RX) and 9 (TX). The schematic is based on the XL1192S IC as shown in circuits/Daikin_P1P2_Uno_version2.pdf. It is a single-sided PCB with SMD components (0805 components, MM1192/XL1192 SOP-16, SI8621 SOIC-8, and a Murata SMD-mounted 5V/5V converter). It provides galvanic isolation to the P1/P2 bus, but it does not support being powered from the P1/P2 bus: you still need a 5V source to power the Arduino Uno, and to power the XL1192 over the DC/DC conveter. Images of the board can be found in the circuits directory.

A variant of this board is based on the newer MAX22088 adapter. It is a very similar 0.5"x2" PCB for the Arduino Uno. Instead of the 5V/5V converter, the adapter receives its power from the MAX22088 (thus from the P1/P2 bus). For safety reasons the adapter still has a Si8621 galvanic isolator, and this adapter does not power the Arduino Uno.

Warning: please note that the XL1192-based circuit may be a burden to the bus if the adapter is not powered (by the Arduino). If unpowered, it is better to disconnect it. This warning does not apply to MAX22088 based circuits.

New software, new name: P1P2MQTT

The program P1P2-bridge-esp8266 wil be revised and will be called P1P2MQTT as it describes its function better: to bridge between P1/P2 2-wire interface and MQTT. The program to run on the ATmega will remain P1P2Monitor. Both are running on the P1P2-ESP-interface hardware.

This project started as a low-level reverse engineering project, and was inspired by AltSoftSerial, hence the name P1P2Serial. This name no longer covers the scope from P1/P2 to MQTT. The project may also be renamed to P1P2MQTT.

Which Daikin systems are supported?

There is a large variation in the P1/P2 logical protocol implementation of various Daikin systems. My system is a Daikin hybrid EHYHBX08AAV3 which is supported: many parameters (power consumption, #hours, #compressor-start, temperatures, etc) can be monitored and various system settings can be controlled. Monitoring the P1/P2 bus on other systems should always be possible, but interpretation of the raw data may require further reverse engineering. It is currently assumed that various Daikin Altherma Hybrid and Daikin Altherma LT models are reasonably similar that they may be supported by changing the parameters used to control certain functions and/or by changing the code which interprets the received data and encodes it into MQTT parameter values.

As we have no access to Daikin's documentation, we do not know which systems are supported. Various users have reported success in basic control functions. In my hybrid system I can control almost all parameters. It is logical to assume that devices supported by commercial auxiliary controllers (Daikin LAN adapter, Zennio KLIC-DA KNX interface, Coolmaster) could be supported by this project.

We have very limited experience with VRV-based systems (systems with multiple indoor ceiling units), of which model numbers start with an "F". These models also use the P1/P2 bus to the controller, with a similar protocol for basic communication, but we don't know how the auxiliary controller communication goes. It should be possible to at least monitor the packets on the bus. If someone figures out how the auxiliary controller protocol works for these systems, it should be possible to set the unit on/off, set operating mode, fan speed level and swing function, and temperature setoint.

COP calculation, defrost energy losses

In addition to monitoring and control, the P1P2-ESP-interface also calculates the COP (coefficient of performance) values (this function will be released in the future).

Both long-term and actual COP values are calculated.

The long-term average COP value is calculated once per day, week, month, or year. The calculation can be based on -the energy production counter as hourly reported by the Daikin unit, and as calculated based on delta-T and flow integrated over time -the energy consumption counter as reported by the Daikin unit (which is only updated once per hour), or better, if available, from an external electricity meter.

The day-average outside temperature is also calculated for comparison as the COP heavily depends on that temperature. The outside temperature is averaged only over the time the heat pump was switched on.

The current COP value is calculated every second and averaged over a predetermined time length and is based on -the actual energy production as calculated based on the actual delta-T and actual flow -the energy consumption based on an external electricity meter.

ESPAltherma also reports energy consumption (or actually current and voltage) but the readings from my Daikin system are not very accurate, its resolution in my system is 115Watt.

Some newer Daikin hybrid systems do not seem to measure water flow and are not able to calculate heating energy produced. This means it may be fundamentally impossible to calculate heating power and COP without additional external flow sensor.

No liability, no warranty

Any use is entirely at your own risk (CC BY-NC-ND 4.0 Section 5 applies, for earlier versions GPL sections 11 and 12 apply).

Is it safe?

There is always a risk when you write to the bus based on reverse engineering and assumptions that unexpected things happen or break. Reading without writing should be safe though. My system has been running continuously in controller mode (writing and reading) for 3 years now. Still, use is entirely at your own risk.

It is advised to connect/disconnect devices to the P1/P2 bus only if the power of all connected devices is switched off. Some Daikin manuals warn that device settings should not be changed too often, because of wear in the solid state memory in their devices - one of their manuals states a maximum of 7000 setting changes per year - without indicating the expected life time of their product. Don't change settings too often.

How to get started / and is my system supported?

If your system has a P1/P2 connection to the main controller or room thermostat, you will almost certainly be able to monitor raw data from the P1/P2 bus. P1P2Monitor and P1P2MQTT/P1P2-bridge-esp8266 will try to interpret the data, reported as parameters. This may be more or less succesful, hopefully the interpreted data makes sense. If not, you may look at the raw data patterns, and try to understand these and compare these with the examples in the doc folder.

If, like many systems, your system communicates with a repeating pattern of packages made of request/response pairs of packet types 10-15/16, followed by a single request packet with header 00F030, you may be lucky. If the 00F030 request is followed by a longer pause (100-200ms), and no answer 40F030, the P1P2Monitor might function as an auxiliary controller responding to that request. If you switch P1P2Monitor controller functionality on (by sending "*" followed by "l1" to MQTT channel P1P2/W/\<xxx>), it will start replying to each 00F030 packet with a 40F030 response after which more 00F03x/40F04x packets are exchanged. These packets are likely similar to but different than the example system. Parameters for switching certain functions on/off may depend on the model and do depend on which control mode the system is operating in. It is useful to monitor the system for a while in this mode, and important to first check that there are no read errors or bus collissions.

When an auxiliary controller starts to be active, the main controller will regularly communicate all parameters to the auxiliary controller. To communicate all parameters takes a few minutes. In addition, any parameter changed on the main controller will almost immediately be communicated. By default, P1P2-ESP filters any parameter of which the value has not changed. After a few minutes its output will get mostly silent. If the time (minute and perhaps second) is part of the data, you will see time progress. You will likely see some reports when temperature measurements vary. And if everything works well you should see any manual changes made on the main controller be reported. It is useful to record which parameters are

If you start monitoring and you find that there is already an answer 40F030 in your system, this may be due to a Daikin LAN module or other auxiliary controller in your system. It may even be part of your main Daikin system itself. In that case it is useful to