Hitachi H-link2 - support for writing to the P1P2 bus

[user890104]

We have a Hitachi H-link2 system installed at our office. There is a P1P2MQTT bridge made by Arnold that we installed and we can see the raw packets going back and forth. But we are unable to control the units, since writing to the bus is not implemented.

We also have a spare remote control, but unsure if it can be of any use for debugging/reversing the protocol needed for write support on the bus.

This is our reverse-engineering effort so far, based on raw packet sniffing, and chaning the system to run in various modes:
https://docs.google.com/spreadsheets/d/13hszgDAdVjzlA0g9ORPiE48NfMgoU1kxcpj9PWbSJ1w/edit

Please let me know if anything else is needed so that writing to the bus e.g. for replaying command from the remote, can be achieved.

[Arnold-n]

Hi Vencislav,
Many thanks for your support in reverse engineering this - I am very busy in August but will pick up Hitachi support in September again.
For other Hitachi users: please upgrade to at least v0.9.51 which contains some decoding based on Vencislav's analysis.
Kind regards,
Arnold

[user890104]

Hi, just a kind reminder on this. As I said previously, we are open to help understanding the protocol, including hooking up a logic analyzer to the bus and/or sniffing the raw data from the original remote. We don't have access to the central management software, just to our office's units and wall remote control panel, and this is why we need remote access to configure the HVAC system.