Documentation for hardware configuration?

[rnewman]

The README in the repo explains how to flash a device with esphome, but I don't see any documentation for what connector and connection is necessary, or where to connect to the Navien unit.

I can probably figure out the latter, but it would probably encourage more testers if this were a paved path.

From reading around, the connector seems to be a keyed JST-XH(B) connector. Does this need to go via a second board (e.g., the M5 commu) or can it be wired directly to a 4-pin Grove connector? What is the pin ordering needed (if building a cable) or what is the appropriate cable to buy?

I have a NCB 240/130H combi boiler and would be happy to test, but right now I have a NanoC6 and a few components, but little knowledge about how to connect that to the Navien.

[sreknob]

Just made a cable yesterday to get this going. Lots of information on the HA community thread. Still need to flash my ESP though!

The connector on the Navien is a 5-pin JST connector, locking or non-locking both work. I used some 2.54mm JST-XHP I had in the drawer and they work perfectly. Seems like the connector location may vary depending on the model (sometimes left and sometimes right of the control board), but it should be the only 5-pin connector on the main controller. Pinout is here in the thread and here is the cable that I copied to make mine.

Below is what the pinout should be, looking at the JST connector from the side with the slots and/or locking tab with the wires towards the bottom of the connector image:

 ┌──────┬─┬──────────────┬─┬──────┐ 
 │      │ │              │ │      │ 
 │      │ │              │ │      │ 
 │      │ │              │ │      │ 
 │      │ │              │ │      │ 
 │      │ │              │ │      │ 
┌┴──────┴─┴──────────────┴─┴──────┴┐
└──────────────────────────────────┘
   ▲      ▲       ▲      ▲      ▲   
   │      │       │      │      │   
   │      │       │      │      │   
                                    
  GND    Not   RS485A  RS485B  12V  
      Connected  (-)     (+)        

You cannot hook up directly to a Grove connector as the Navian 485 bus works at 12V and this will let the magic smoke out of your ESP. You need an RS485 adapter to allow communication at TTL levels for the ESP. Some adapters can back-power the ESP via a DC-DC voltage regulator like the M5Stack Base or Tail units to step down to VCC for the ESP.

Hope this helps!

[htumanyan]

Hello!
First of all, I am sorry for taking forever to respond - this is my night and weekend project that got preempted by urgent work stuff.

Your cable pinout seems accurate - you are correct in that it varies from mode to model. The most important pins to find are ground, and rs485 differential pins. The ground should be easy to track with ohm meter or other probe - it should be connected to the body. The other two pins are usually in the middle as you had on your drawing. You just need to experiment - sometimes swap the two pins (the esp will produce gibberish if pins are inverted).

You cannot hook up directly to a Grove connector as the Navian 485 bus works at 12V and this will let the magic smoke out of your ESP
Absolutely. Some people on the forum successfully used M5 Atom with relevant rs485 option. I use a custom designed hardware board (published under hardware in this repo), which I plan to produce in small batches for everyone interested (works on my unit now).

Feel free to ask any questions if I can help in any way.