A MQTT bridge for Solis solar inverters.

Introduction

Solis solar inverters are equipped with an RS485 interface, through which telemetry values can be read and also control commands can be sent. The manufacturer offers LAN and WLAN sticks in combination with a software solution to access the interface. Unfortunately, this is always coupled with a connection to the manufacturer's cloud and integration into a home automation system is only possible in a detoured manner. This software acts as a bridge between the RS485 interface and a MQTT broker to allow easy integration into a home automation (with special support for Home Assistant), and furthermore without cloud constraints.

Hardware

• The inverter uses a proprietary(?) RS485 plug, with the following pin-out:

  /-----\
  | 2 3 |
  | 1 4 |
  \--^--/

1. +5V
2. GND
3. DATA+
4. DATA-

• Any RS485 adapter should do. I use one of these (with FTDI chip), but have also tested this simple (and cheaper) one.
• I highly recommend using a proper connector, which can be found on ebay (search for "RS485 Solis" or "Exceedconn EC04681-2014-BF") and solder the wires to it.
• I run the software on a RaspberryPi Zero W, but any Linux box should do.

Installation

• Download and install to /opt/solis2mqtt

wget https://github.com/incub77/solis2mqtt/archive/main.tar.gz -O - | sudo tar -xvzf - --one-top-level=/opt/solis2mqtt --strip 1

• Execute setup.sh. This will basically install dependencies, add a system user for the daemon to run in and setup systemd.

sudo bash /opt/solis2mqtt/setup.sh

• Edit config.yaml. See section Basic Configuration.

e.g. sudo vi /opt/solis2mqtt/config.yaml

• A reboot is necessary for user rights (access to /dev/ttyUSB*) to become effective.

sudo reboot

Usage

Solis2MQTT is intended to run as a system service. A log file is written to /opt/solis2mqtt/solis2mqtt.log. To control the service, the usual systemd commands are used:

• Start: sudo systemctl start solis2mqtt
• Stop: sudo systemctl stop solis2mqtt
• Restart: sudo systemctl restart solis2mqtt
• Disable start on boot: sudo systemctl disable solis2mqtt
• Enable start on boot: sudo systemctl enable solis2mqtt

To check if the service is running you can do a ps -efH | grep solis2mqtt. The output should look something like this:

solis2m+   460     1  0 22:53 ?        00:00:08   /usr/bin/python3 solis2mqtt.py -d
pi         559   501  0 23:13 pts/0    00:00:00           grep --color=auto solis2mqtt

If Solis2MQTT doesn't start up to a point where the log file is written you can check /var/log/syslog for clues.

For development/debugging Solis2MQTT can also be started directly. Make sure to change to the working directory before doing so.

cd /opt/solis2mqtt
python3 ./solis2mqtt.py

The following command line arguments are implemented:

• -d Start as a daemon. Otherwise, Solis2MQTT will stay attached to your shell and writes log messages to stdout/stderr.
• -v Verbose mode. Will output debug logging messages.
• --help ...

Basic Configuration

Configuration is read from config.yaml, that has to contain at least these entries:

device: /dev/ttyUSB0
mqtt:
  url: hassio.local
  user: whoami
  passwd: secret

This is a complete config example:

device: /dev/ttyUSB0
slave_address: 1
poll_interval: 60
poll_interval_if_off: 600
inverter:
    name: solis2mqtt
    manufacturer: Ginlong Technologies
    model: solis2mqtt
mqtt:
    url: hassio.local
    port: 8883
    use_ssl: true
    validate_cert: true
    user: whoami
    passwd: secret

• device: [Required] The path to your RS485 adapter
• slave_address: [Optional] The modbus slave address, default is 1
• poll_interval: [Optional] Inverter poll interval in seconds, default is 60
• poll_interval_if_off: [Optional] Poll interval during night in seconds, default is 600
• interter:
  • name: [Optional] Used as a base path in MQTT, default is solis2mqtt
  • manufacturer: [Optional] Used for device info in Home Assistant, default is incub
  • model: [Optional] Used for device info in Home Assistant, default is solis2mqtt
• mqtt:
  • url: [Required] URL to your MQTT broker
  • port: [Optional] Port of your MQTT broker, default is 8883
  • use_ssl: [Optional] Use SSL for MQTT traffic encryption, default is true
  • validate_cert [Optional] Validate certificate for SSL encryption, default is true
  • user: [Required] User for MQTT broker login
  • passwd: [Required] Password for MQTT broker login

Inverter configuration

The file solis_modbus.yaml contains a list of entries, that describe the values to read from (and write to) the inverter.
You can add your own entries if you want to read other metrics from the inverter. Especially if it comes to writing to the inverter - use at your own risk :-)
This is an example of an entry:

- name: inverter_temp
  description: Inverter temperature
  unit: "°C"
  active: true
  modbus:
    register: 3041
    read_type: register
    function_code: 4
    number_of_decimals: 1
    signed: false
  homeassistant:
    device: sensor
    state_class: measurement
    device_class: temperature

The following options are available:

• name: [Required] Has to be unique. Used in MQTT path and together with the inverter name (from config.yaml) as part of Home Assistant unique_id
• description: [Required] Used for generating log messages and as display name in Home Assistant
• unit: [Optional] Added to log messages and used for Home Assistant
• active [Required] Set to false if the entry should be ignored
• modbus: [Required]
  • register: [Required] The modbus register address to read/write
  • read_type: [Required] The modbus data type. Currently register and long are supported. Additionally composed_datetime can also be used here (see below)
  • function_code: [Required] The modbus function code to read the register
  • write_function_code: [Optional] The function code to write to the register
  • number_of_decimals: [Optional] Can only be used in combination with ready_type: register. Used for automatic content conversion, e.g. 101 with number_of_decimals: 1 is read as 10.1
  • signed: [Required] Whether the data should be interpreted as signed or unsigned
• homeassistant: [Optional]
  • device: [Required] Used for Home Assistant MQTT discovery. Can either be sensor, number or switch
  • state_class: [Optional] State class for Home Assistant sensors
  • device_class: [Optional] Device class for Home Assistant sensors
  • payload_on: [Optional] In combination with device: switch required. Specifies the payload that indicates the switch is in 'on' position
  • payload_off: [Optional] In combination with device: switch required. Specifies the payload that indicates the 'off' position
  • min: [Optional] In combination with device: number required. Specifies minimum value.
  • max: [Optional] In combination with device: number required. Specifies maximum value.
  • step: [Optional] In combination with device: number required. Specifies step value. Smallest value 0.001.

Special case for datetime

As the datetime information is stored in several registers, there is a special read_type to read this as one ISO datetime string.

- name: system_datetime
  description: System DateTime
  unit:
  active: true
  modbus:
    register: [3072, 3073, 3074, 3075, 3076, 3077] # [year, month, day, hour, minute, seconds]
    read_type: composed_datetime
    function_code: 4
  homeassistant:
    device: sensor
    state_class:
    device_class: timestamp

Screenshots