Poll Trigger (POLL_TRIGGER)

Overview

Poll trigger (triggerType = 5) is used for periodic condition evaluation of local data sources. Primarily applied to Modbus slave sensor data collection, it also supports condition evaluation of local sensor cache data.

Trigger	Input Source	Check Timing	Suitable Scenarios	Common Risks
Platform Trigger	MQTT platform command	Match fields immediately upon message arrival	Remote on/off, parameter delivery, linkage control	Inconsistent field names, duplicate messageId, insufficient permissions
Timer Trigger	Local clock / cron / interval	Execute when time point is reached	Periodic reporting, scheduled on/off, night mode	NTP not synced, first trigger semantics unclear
Event Trigger	Button, sensor, system events	Match eventId when event is published	Button control, threshold alarm, state change	Debouncing, event name spelling, cached value expiry
Poll Trigger	Actively read peripheral or protocol data	Check conditions every pollInterval	Modbus collection, analog threshold, distance alarm	Too frequent, serial port busy, low memory frequency reduction

Poll trigger actively consumes peripheral, serial port, or bus resources. Before configuring, confirm whether an event source is already available; only use poll trigger when there is no event source or periodic sampling is required.

Trigger Mechanism

1. Periodically triggers at intervalSec intervals
2. Executes data collection actions in the action list (e.g., MODBUS_POLL, SENSOR_READ)
3. Collected data is evaluated against the trigger's compareValue condition
4. If conditions are met, the trigger is completed and data is reported

Field Description

Field	Type	Description
triggerType	5	Poll trigger
timerMode	0	Interval mode (poll trigger only supports interval)
intervalSec	uint32	Poll interval in seconds
pollResponseTimeout	uint16	Modbus response timeout (ms), default 1000
pollMaxRetries	uint8	Maximum retry count, default 2
pollInterPollDelay	uint16	Minimum interval between two requests (ms), default 100

Difference from Timer Trigger

Feature	TIMER_TRIGGER	POLL_TRIGGER
triggerType	1	5
Condition Evaluation	Does not evaluate conditions	Can evaluate collected data
Communication Parameters	None	Timeout/retry/interval
Use Case	Simple timing	Modbus/sensor polling

Configuration Examples

Method 1: Web Interface Configuration (Recommended)

The peripheral execution page is shown below. When configuring poll trigger, verify the target data source, comparison value, poll interval, and execution action duration.

Example 1: Modbus Sensor Polling (Every 5 Minutes)

Scenario: Collect Modbus sensor data every 5 minutes

Configuration Steps:

1. Click Peripheral Execution in the left menu

2. Click the Add Rule button

3. Fill in basic configuration:

   • Rule Name: Modbus Environment Data Collection
   • Report Data: ✅ Enabled (auto-report collection results)
   • Enable: ✅ Enabled

4. Configure trigger:

   • Trigger Type: Select Poll Trigger
   • Poll Interval: Enter 300 (300 seconds = 5 minutes)
   • Response Timeout: Enter 1000 (1000ms, default)
   • Max Retries: Enter 2 (default)
   • Request Interval: Enter 100 (100ms, default)

5. Configure action:

   • Action Type: Select Modbus Poll
   • Target Peripheral: Select the corresponding Modbus task

6. Click the Save button

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Example 2: Polling with Condition Evaluation

Scenario: Only report when polled data > 500

Configuration Steps:

1. Create rule, name: Smoke Exceedance Alarm
2. Trigger configuration:
   • Trigger Type: Select Poll Trigger
   • Target Peripheral ID: Enter smoke_sensor
   • Operator: Select Greater Than (>)
   • Threshold: Enter 500
   • Poll Interval: Enter 60 (60 seconds)
3. Configure actions:
   • Action 1: Select Sensor Read, target smoke_sensor
   • Action 2: Select alarm-related actions
4. Click Save

💡 Tip: Condition evaluation is automatically performed after data collection; subsequent actions only execute when conditions are met

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Method 2: JSON Configuration File Import

Complete Rule Example

Modbus Environment Data Collection

{
  "id": "exec_env_poll",
  "name": "Collect Environment Quality",
  "enabled": false,
  "execMode": 0,
  "triggers": [
    {
      "triggerType": 5,
      "triggerPeriphId": "",
      "operatorType": 0,
      "compareValue": "",
      "timerMode": 0,
      "intervalSec": 300,
      "timePoint": "",
      "eventId": "",
      "pollResponseTimeout": 1000,
      "pollMaxRetries": 2,
      "pollInterPollDelay": 100
    }
  ],
  "actions": [
    {
      "targetPeriphId": "modbus-task:0",
      "actionType": 18,
      "actionValue": "{\"poll\":[0]}",
      "useReceivedValue": false,
      "syncDelayMs": 0,
      "execMode": 0
    },
    {
      "targetPeriphId": "modbus-task:1",
      "actionType": 18,
      "actionValue": "{\"poll\":[1]}",
      "useReceivedValue": false,
      "syncDelayMs": 200,
      "execMode": 0
    }
  ],
  "protocolType": 0,
  "scriptContent": "",
  "reportAfterExec": true
}

Communication Parameter Tuning

Scenario	pollResponseTimeout	pollMaxRetries	pollInterPollDelay
Short-range RS485	500	1	50
Long-range RS485	2000	3	200
Multi-device bus	1000	2	150

Precautions

1. Modbus Availability: Poll trigger checks if Modbus is available; skips if unavailable
2. Running Protection: Skips current trigger if previous poll has not completed
3. Failure Backoff: After execution failure, enters 30-second backoff period to avoid frequent retries
4. Resource Protection: Heavy-resource rules (scripts/Modbus/multi-action) are skipped rather than degraded to sync when system resources are low
5. Data Reporting: When reportAfterExec: true, MODBUS_POLL and SENSOR_READ results are automatically reported via MQTT