Installation and Configuration

Install the binary

The minimum Go version required is 1.19.

go install github.com/candlerb/solis_exporter/cmd/solis_exporter@latest

This should install the binary in ~/go/bin/solis_exporter

Configure Exporter

The exporter is configured using a YAML file solis_exporter.yml. The location of the config file is given using the -config flag, e.g.

./solis_exporter -config /etc/solis_exporter.yml

The configuration file has only a few required settings:

serial:
  device: /dev/ttyUSB0
  #dump: true

solis_exporter:
  listen: ':3105'

"dump" shows all the packet exchanges on RS485 in raw hex.

You can run the exporter under systemd, using the sample service file. You may need to tweak this: e.g. to change the user that the daemon runs as. This user must have permission to open the serial device.

sudo cp solis_exporter.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable --now solis_exporter

Reading metrics

Metrics are available on the given port under /metrics. You can read them using:

curl 127.0.0.1:3105/metrics

Most metrics will not appear until the first successfully sniffed packet exchanges.

Dashboard

Once the exporter is running, you can configure prometheus with a scrape job to read metrics periodically:

  - job_name: solis
    scrape_interval: 1m
    static_configs:
      - targets:
          - x.x.x.x:3105

Grafana dashboard 17503 provides a basic set of graphs from data stored in prometheus.

Modbus TCP gateway

The optional modbus TCP gateway facility allows you to inject messages onto the RS485 bus, to query or change the inverter settings.

To enable this feature, add a stanza to solis_exporter.yml like this:

gateway:
  listen: '127.0.0.1:1502'
  rules:
    - from: 10001
      to: 19999
      functions: [2]
    - from: 30001
      to: 39999
      functions: [3,4]
    - from: 40001
      to: 49999
      functions: [3]

Port

If you prefer to listen on the standard modbus TCP port 502, you will need to give the program permission to bind to privileged ports. This can be done by running the exporter as root, or you can give it the NET_BIND_SERVICE capability. If running as a service under systemd, you can use these settings:

[Service]
...
CapabilityBoundingSet=CAP_NET_BIND_SERVICE
AmbientCapabilities=CAP_NET_BIND_SERVICE

Rules

The gateway "rules" allow you to limit which function codes and register ranges are accepted in TCP modbus requests. Only register ranges and codes which match a rule are permitted. I recommend you limit access to function codes 6 (write single) and 16 (write multiple) to small ranges of registers that you are sure are safe to update. Note that no validation of the values written to those registers is performed, only the register ranges.

Usage

You can connect to the gateway with any client which speaks the simple modbus TCP protocol. Only a limited set of modbus commands are currently implemented; if you send any messages which are not understood, the TCP connection will be dropped.

You need to use a high response timeout of around 10 seconds. This is because if you try to inject a message at the same time as the data logger is communicating with the inverter, solis_exporter will wait until the line is idle.