Example 3B: Command Script Flowing Light

fastbeeAbout 4 min

Example 3B: Command Script Flowing Light

Experiment Overview

Use FastBee's Command Script Action (ACTION_SCRIPT) to achieve LED flowing light effects through PERIPH and DELAY command sequences. Unlike JavaScript scripts, command scripts use declarative command sequences that are more intuitive and readable.

Hardware Wiring

Board Label	GPIO Pin	Connected Device
D1	GPIO15	LED1 (active-low)
D2	GPIO2	LED2 (active-low)
D3	GPIO0	LED3 (active-low)
D4	GPIO4	LED4 (active-low)

Method 1: Basic Sequential Flowing Light

Peripheral Execution Rule Configuration

{
  "id": "rule_cmd_flow_basic",
  "name": "Command Script - Basic Flowing Light",
  "enabled": true,
  "triggers": [
    { "type": "manual" }
  ],
  "actions": [
    {
      "type": 15,
      "actionType": 15,
      "actionValue": "PERIPH cmd_led1 LOW\nDELAY 300\nPERIPH cmd_led1 HIGH\nPERIPH cmd_led2 LOW\nDELAY 300\nPERIPH cmd_led2 HIGH\nPERIPH cmd_led3 LOW\nDELAY 300\nPERIPH cmd_led3 HIGH\nPERIPH cmd_led4 LOW\nDELAY 300\nPERIPH cmd_led4 HIGH\nLOG Basic flowing light cycle complete",
      "execMode": 0
    }
  ]
}

Command Script Breakdown

PERIPH cmd_led1 LOW      # Turn on LED1 (active-low)
DELAY 300                # Delay 300ms
PERIPH cmd_led1 HIGH     # Turn off LED1 (active-high)
PERIPH cmd_led2 LOW      # Turn on LED2
DELAY 300                # Delay 300ms
PERIPH cmd_led2 HIGH     # Turn off LED2
... (repeat sequentially)
LOG Basic flowing light cycle complete    # Print log

Execution Methods

Manual Trigger: Manually trigger the rule via API or Web interface
API Call: POST /api/periph-exec/rules/rule_cmd_flow_basic/trigger

Method 2: Timer Auto-Cycle Flowing Light

Peripheral Execution Rule Configuration

{
  "id": "rule_cmd_flow_timer",
  "name": "Command Script - Timer Cycle Flowing Light",
  "enabled": true,
  "triggers": [
    {
      "type": "timer",
      "params": {
        "interval": 1500,
        "repeat": -1
      }
    }
  ],
  "actions": [
    {
      "type": 15,
      "actionType": 15,
      "actionValue": "PERIPH cmd_led1 LOW\nDELAY 300\nPERIPH cmd_led1 HIGH\nPERIPH cmd_led2 LOW\nDELAY 300\nPERIPH cmd_led2 HIGH\nPERIPH cmd_led3 LOW\nDELAY 300\nPERIPH cmd_led3 HIGH\nPERIPH cmd_led4 LOW\nDELAY 300\nPERIPH cmd_led4 HIGH",
      "execMode": 0
    }
  ]
}

Configuration Notes

interval: 1500 - Execute one cycle every 1.5 seconds (4 LEDs × 300ms + delay margin)
repeat: -1 - Infinite loop
No manual trigger needed; runs automatically after system startup

Method 3: Bidirectional Flowing Light

Peripheral Execution Rule Configuration

{
  "id": "rule_cmd_flow_bidirectional",
  "name": "Command Script - Bidirectional Flowing Light",
  "enabled": true,
  "triggers": [
    {
      "type": "timer",
      "params": {
        "interval": 2500,
        "repeat": -1
      }
    }
  ],
  "actions": [
    {
      "type": 15,
      "actionType": 15,
      "actionValue": "PERIPH cmd_led1 LOW\nDELAY 200\nPERIPH cmd_led1 HIGH\nPERIPH cmd_led2 LOW\nDELAY 200\nPERIPH cmd_led2 HIGH\nPERIPH cmd_led3 LOW\nDELAY 200\nPERIPH cmd_led3 HIGH\nPERIPH cmd_led4 LOW\nDELAY 200\nPERIPH cmd_led4 HIGH\nPERIPH cmd_led3 LOW\nDELAY 200\nPERIPH cmd_led3 HIGH\nPERIPH cmd_led2 LOW\nDELAY 200\nPERIPH cmd_led2 HIGH",
      "execMode": 0
    }
  ]
}

Execution Sequence

LED1 → LED2 → LED3 → LED4 → LED3 → LED2 → (cycle)

Achieves a "ping-pong" back-and-forth effect.

Method 4: Accumulative Brightening Flowing Light

Peripheral Execution Rule Configuration

{
  "id": "rule_cmd_flow_accumulate",
  "name": "Command Script - Accumulative Flowing Light",
  "enabled": true,
  "triggers": [
    {
      "type": "timer",
      "params": {
        "interval": 2000,
        "repeat": -1
      }
    }
  ],
  "actions": [
    {
      "type": 15,
      "actionType": 15,
      "actionValue": "PERIPH cmd_led1 LOW\nDELAY 200\nPERIPH cmd_led2 LOW\nDELAY 200\nPERIPH cmd_led3 LOW\nDELAY 200\nPERIPH cmd_led4 LOW\nDELAY 500\nPERIPH cmd_led1 HIGH\nPERIPH cmd_led2 HIGH\nPERIPH cmd_led3 HIGH\nPERIPH cmd_led4 HIGH",
      "execMode": 0
    }
  ]
}

Effect Description

LEDs turn on sequentially without turning off
After all 4 LEDs are on, delay 500ms
Then all turn off, start next cycle

Method 5: Random Flowing Light (with MQTT Command)

Peripheral Execution Rule Configuration

{
  "id": "rule_cmd_flow_random",
  "name": "Command Script - Random Flowing Light",
  "enabled": true,
  "triggers": [
    {
      "type": "timer",
      "params": {
        "interval": 500,
        "repeat": -1
      }
    }
  ],
  "actions": [
    {
      "type": 15,
      "actionType": 15,
      "actionValue": "PERIPH cmd_led1 HIGH\nPERIPH cmd_led2 HIGH\nPERIPH cmd_led3 HIGH\nPERIPH cmd_led4 HIGH\nMQTT 0 [{\"id\":\"flow_state\",\"value\":\"RANDOM(1,4)\"}]\nLOG Random flowing light triggered",
      "execMode": 0
    },
    {
      "type": 10,
      "actionType": 10,
      "targetPeriphId": "cmd_led{{received.value}}",
      "actionValue": "LOW",
      "useReceivedValue": false,
      "execMode": 0
    }
  ]
}

Description

Uses RANDOM(1,4) to generate random number
Reports currently lit LED number via MQTT
Randomly lights one of the LEDs

Command Script Syntax Reference

Supported Commands

Command	Format	Description
PERIPH	`PERIPH <id> <action> [value]`	Control peripheral
DELAY	`DELAY <ms>`	Delay (milliseconds)
LOG	`LOG <message>`	Print log
MQTT	`MQTT <qos> <payload>`	Send MQTT message

PERIPH Sub-commands

Sub-command	Format	Description
HIGH	`PERIPH <id> HIGH`	Output HIGH
LOW	`PERIPH <id> LOW`	Output LOW
PWM	`PERIPH <id> PWM <value>`	Set PWM value (0-4095)
BLINK	`PERIPH <id> BLINK <interval_ms>`	Blink
COLOR	`PERIPH <id> COLOR <#RRGGBB>`	NeoPixel color

Command Separator

Use \n (newline) to separate multiple commands
Must be escaped as \\n in JSON

Command Script vs JavaScript Script Comparison

Feature	Command Script (ACTION_SCRIPT)	JavaScript Script
Syntax	Declarative command sequence	Programming language
Readability	⭐⭐⭐⭐⭐ Very intuitive	⭐⭐⭐ Requires programming knowledge
Flexibility	⭐⭐⭐ Fixed command set	⭐⭐⭐⭐⭐ Completely free
Performance	⭐⭐⭐⭐ Lightweight parsing	⭐⭐⭐ Requires JS engine
Use Case	Simple timing control, debugging	Complex logic, computation
Variable Support	❌ Not supported	✅ Supports getVar/setVar
Conditional	❌ Not supported	✅ Supports if/else
Loop	❌ Not supported (use timer instead)	✅ Supports for/while

Selection Recommendations

✅ Use Command Script: Simple timing, beginners, rapid prototyping, peripheral debugging
✅ Use JavaScript Script: Complex logic, state machines, dynamic computation, conditional branching

Notes

Command Length Limit: Single actionValue recommended not to exceed 512 characters
DELAY Accuracy: Actual delay may have ±10ms error
GPIO0 Limitation: Do not pull GPIO0 LOW during boot, otherwise enters download mode
Blocking Execution: Command scripts execute synchronously; DELAY blocks subsequent commands
Trigger Frequency: Timer interval should be greater than total script execution time to avoid queue buildup
Log Output: Use LOG command to track script execution progress for debugging
Error Handling: If peripheral ID in PERIPH command does not exist, it will be skipped and execution continues

Extended Exercises

Exercise 1: Breathing Light Effect

Use PWM commands to achieve LED breathing effect:

{
  "actionValue": "PERIPH cmd_led1 PWM 0\nDELAY 50\nPERIPH cmd_led1 PWM 512\nDELAY 50\nPERIPH cmd_led1 PWM 1024\nDELAY 50\nPERIPH cmd_led1 PWM 2048\nDELAY 50\nPERIPH cmd_led1 PWM 4095\nDELAY 50\nPERIPH cmd_led1 PWM 2048\nDELAY 50\nPERIPH cmd_led1 PWM 1024\nDELAY 50\nPERIPH cmd_led1 PWM 512\nDELAY 50\nPERIPH cmd_led1 PWM 0"
}

Exercise 2: Traffic Light Simulation

Use 3 LEDs to simulate red/yellow/green traffic light:

{
  "actionValue": "PERIPH led_red LOW\nDELAY 3000\nPERIPH led_red HIGH\nPERIPH led_yellow LOW\nDELAY 1000\nPERIPH led_yellow HIGH\nPERIPH led_green LOW\nDELAY 3000\nPERIPH led_green HIGH\nLOG Traffic light cycle complete"
}

Exercise 3: Morse Code

Use LED to send SOS signal:

{
  "actionValue": "PERIPH cmd_led1 LOW\nDELAY 200\nPERIPH cmd_led1 HIGH\nDELAY 200\nPERIPH cmd_led1 LOW\nDELAY 200\nPERIPH cmd_led1 HIGH\nDELAY 200\nPERIPH cmd_led1 LOW\nDELAY 200\nPERIPH cmd_led1 HIGH\nDELAY 600\nPERIPH cmd_led1 LOW\nDELAY 600\nPERIPH cmd_led1 HIGH\nDELAY 600\nPERIPH cmd_led1 LOW\nDELAY 600\nPERIPH cmd_led1 HIGH\nDELAY 600\nPERIPH cmd_led1 LOW\nDELAY 600\nPERIPH cmd_led1 HIGH\nDELAY 600\nPERIPH cmd_led1 LOW\nDELAY 200\nPERIPH cmd_led1 HIGH\nDELAY 200\nPERIPH cmd_led1 LOW\nDELAY 200\nPERIPH cmd_led1 HIGH\nDELAY 200\nPERIPH cmd_led1 LOW\nDELAY 200\nPERIPH cmd_led1 HIGH\nLOG SOS complete"
}

Tip: Command scripts are ideal for quick verification of peripheral functions and simple timing control. For more complex logic, refer to 03-led-flowing.md for JavaScript script implementation.