#Device Commands (ISDU)

iolinkmaster2mqtt exposes device commands over MQTT. Any client can send a command by publishing to the command topic; results are returned on a paired result topic. Rules can also issue commands as actions by publishing to the same param/<command> topics.

#Topic layout

<topic_prefix>/<device_name>/param/<command>           # send command (publish here)
<topic_prefix>/<device_name>/param/<command>/result    # response (subscribe here)
<topic_prefix>/<device_name>/param/commands            # retained: available commands

Example with defaults: iolink/vibration1/param/reset_alerts, iolink/vibration1/param/reset_alerts/result.

#Discovering commands

At startup, a retained message is published to each device's param/commands topic listing all available commands. The discovery message at <discovery_prefix>/<topic_prefix>/<device_name> also includes a topics.commands entry pointing to this topic.

Subscribe to <topic_prefix>/<device_name>/param/commands to get:

[
  {
    "name": "reset_alerts",
    "desc": "Reset all present alerts (SystemCommand 229)"
  },
  {
    "name": "select_profile",
    "desc": "Select process data value profile (a-rms, v-rms, x-axis, y-axis, z-axis, user)",
    "params": { "profile": "string" }
  },
  {
    "name": "find_me",
    "desc": "Flash LED for device identification",
    "params": { "enable": "boolean" }
  }
]

Each entry has:

Field	Description
`name`	Command identifier — used as the last segment of the command topic.
`desc`	Human-readable description.
`params`	Optional. Parameter names mapped to type hints (`string`, `number`, `boolean`). Absent if the command takes no parameters.

#Sending a command

Publish a JSON object to <topic_prefix>/<device_name>/param/<command>:

Topic:   iolink/vibration1/param/select_profile
Payload: {"profile": "v-rms"}

For commands with no parameters, publish {}:

Topic:   iolink/vibration1/param/reset_alerts
Payload: {}

No special QoS or retain flags required. Fire-and-forget (QoS 0) is fine.

#Receiving results

Subscribe to <topic_prefix>/<device_name>/param/<command>/result. The response is published after the ISDU operation completes.

#Success (write command)

{ "ok": true }

#Success (read command)

{
  "ok": true,
  "current": 45,
  "max_all_time": 52,
  "min_all_time": 18,
  "max_since_reset": 48,
  "min_since_reset": 22
}

Read commands return "ok": true plus decoded fields. Field names and types depend on the command.

#Error

{
  "ok": false,
  "error": "sick_mpb10: unknown profile \"foo\""
}

Errors are returned for: unknown device, unknown command, invalid parameters, ISDU read/write failure, or decode failure.

#SICK MPB10 commands

Command	Params	Type	Description
`select_profile`	`profile`: string	write	Set process data profile: `a-rms`, `v-rms`, `x-axis`, `y-axis`, `z-axis`, `user`
`read_profile`	—	read	Current profile name
`read_temperature`	—	read	Temperature: current, max, min (all-time and since reset)
`reset_temp_peaks`	—	write	Reset temperature min/max values
`set_temp_limits`	`high`: number, `low`: number	write	Set temperature alert limits (signed int8, °C)
`reset_accel_peaks`	—	write	Reset acceleration peak values
`trigger_acquisition`	—	write	Trigger manual vibration data acquisition
`reset_rms_minmax`	—	write	Reset RMS statistical min/max values
`read_vrms`	—	read	V-RMS X/Y/Z/Magnitude
`read_arms`	—	read	A-RMS X/Y/Z/Magnitude
`read_severity_zone`	—	read	Current severity zone (0–4)
`find_me`	`enable`: boolean	write	Flash LED for device identification
`configure_user_slot`	`slot`: number (0–3), `measurement`: string	write	Assign measurement to user profile slot
`read_user_slots`	—	read	Current user profile slot assignments
`reset_alerts`	—	write	Reset all present alerts

#Notes

Commands are not authenticated beyond MQTT broker ACLs. Any client with publish access to the topic can send commands.
Results are not retained. Subscribe to the result topic before sending the command.
The commands listing topic is retained and republished on MQTT reconnect.
Write commands that change driver state (e.g., select_profile) automatically update the driver's internal decoding, so subsequent process data reflects the new configuration.