This repository contains an ESPHome package for controlling a Dantherm dehumidifier in Home Assistant. It works for my CDP 40 unit, and based on Dantherm's documentation I expect it to work for all CDP, CDP-T and CDF units.

The code in this repository is not enough on its own. You'll need a circuit board for ESPHome, and you'll need to modify an Ethernet cable, but it can all be done without soldering.

Use a board that's compatible with ESPHome and has an RS-485 driver with connections for A, B and GND. I think the proper cabling is to connect A and B via a twisted pair and to connect GND via either another pair and/or or the cable shielding.

The Dantherm unit takes its RS-485 connection via an RJ45 connector. You'll find such a connector at the end of any Ethernet cable, but the pin assignments are different. Numbering the pins from right to left from the perspective of someone looking at the Dantherm unit, pin 1 is A, pin 4 is B, and pin 8 is GND. With this pin assignment, if you use a standard Ethernet cable, A and B will not make up a twisted pair. Things may still work if the cable is short enough, but I haven't tried. Instead I used a crimp tool to attach an RJ45 connector to an Ethernet cable with non-standard wiring such that pin 1 and 4 became a twisted pair.

At the other end of the cable, connect the wires you used for A, B and GND to your board and put a 120 ohm resistor across A and B.

I found a solder-free solution with the LILYGO T-CAN485 board plus a 120 ohm resistor and some Ethernet supplies bought at my local electronics store. The board has Wi-Fi and works with ESPHome, requiring just a USB-C power supply (or 5-12V DC if you prefer).

This repository is intended to be used via the Remote Packages mechanism in ESPHome like so:

packages:
  dantherm:
    url: https://github.com/jbj/dantherm-cdp-cdf
    file: dantherm-cdp-cdf.yaml
    refresh: 0d # Always use the latest version

substitutions:
  dantherm_uart_id: my_uart_id
  # override other variables if needed:
  # dantherm_address

uart:
  id: my_uart_id
  # configure pins and other UART settings for your board

If you use the LILYGO T-CAN485 as described above, you can use the ESPHome package I wrote for it, linking the two packages together by choosing the same UART id:

packages:
  lilygo:
    url: https://github.com/jbj/t-can485-esphome
    file: rs485.yaml
    refresh: 0d
  dantherm:
    url: https://github.com/jbj/dantherm-cdp-cdf
    file: dantherm-cdp-cdf.yaml
    refresh: 0d # Always use the latest version

substitutions:
  # For the `dantherm` package
  dantherm_uart_id: modbus_uart
  # For the `lilygo` package
  rs485_uart_id: modbus_uart

That should be all the configuration you need, plus the parts that Home Assistant generates for you when you create a new device.