This would have been exactly what I needed when I started this journey, preferably with break out terminals for some unused GPIO.
The only thing that I have added above what you suggested is an optocoupler input for the PWM pump control out of the MIM (to get the commanded pump speed without delay) and a PWM output to the pump.
Your project looks great, I will give it a try when I get a bit of time, thanks.
Thanks for all the work and learning by everyone here. I’ve had a Samsung R290 gen7 16kW integrated unit AE160CXYBEK/EU (integrated means that the control board is in the outdoor unit) for 3-4 months and I’m looking at how to measure its performance and potentially integrate it with my Tado TRVs to match the output better to the heat demand in the house (we have an old victorian house with a lot of drafts on a windy day).
It’s taken a while to understand all the different options and the terminology, but as I understand it, I can use F1/F2 with an RS485 adapter to communicate via NASA protocol, but it is a bit more limited (slower responses / updates and not all commands/data available) or I can use F3/F4 with @Topaz‘s hardware. I have an old raspberry pi zero W available that I thought I could use - my home assistant server is not near the heatpump, so I need a wifi connection.
@Topaz can I run your mqtt bridge on a pi zero that’s communicating over F1/F2 via an RS485 adapter? Could you let me know when you restock with your adapter? Can you ship to the UK?
Hello @gmaclennan,
Firstly, latency is not different between F1/F2 or F3/F4.
My work is running ok on the F1/F2 link, but you’ll be limited if you want to input your house’s rooms temperature into the heatpump (My initial goal was to remove the samsung controller completely, which I did in the end).
I ship overall everywhere, I’m undergoing the struggle of JLCPCB parts stock mess. But I should have something early february to order.
Cheers
Thanks for the info @Topaz, I’ll look out for an update here about order availability. When you have the time (which you may well not have!) I’d love to hear more about your setup without the samsung controller (maybe there is something posted somewhere already?). I’m interested in greater control because we have 3 storeys here, an insulated and relatively air-tight lower ground floor which needs very little heat, the ground floor which we keep at 20C, then the 1st floor which is generally at 18C, and more draughty with greater heat loss, so I want to be able to balance the room demand with the heat pump operation.
Well it’s quite simple in fact, as soon as you have a set of indoor temperature sensors, you can aggregate them through your preferred scriptable software (i.e. read Home Assistant here). You can then define threshold for adjusting the hysterisis and reduce it (thanks Samsung for that genereously hardcoded 1°C hysterisis for heating/cooling).
Once done, you just automate the temperature updates from your set of sensors toward samsung’s zones. They only support 2 builtin with their valve control, but if you do some piping and command the additional valve through home assistant while you’re at it, enjoy your infinite zone count :p.
For my pure pleasure, I’ve designed RF 2.4GHz LoRa based sensor mesh network with SX1280 and STM32 with UMQTT over UDP6 over IPv6 transport. It allows my nodes to publish/subscribe to my self hosted MQTT broker (and register directly nice knobs from the stm32). It’s different from using ESP32 as their battery (3.7v 500mAh) lasts more than 2 years. Anyway, that was a long and painful dev, but I really achieve a really smooth integration of all the house… and more to come 
Cheers