Example 4: Buzzer Control

Experiment Overview

Drive a buzzer to produce sound via GPIO output or PWM signal. Passive buzzers require PWM square wave drive (adjustable frequency), while active buzzers only need HIGH/LOW level switching.

Hardware Wiring

Board Label	GPIO Pin	Connected Device
BEEP	GPIO4	Active/Passive buzzer

The Puzhong board buzzer is connected to GPIO4, active buzzer driven by HIGH level.

JSON Configuration Example

{
  "peripherals": [
    {
      "id": "buzzer_gpio",
      "name": "Buzzer-Switch",
      "type": 12,
      "enabled": false,
      "pins": [4],
      "params": {
        "initialState": 0
      }
    },
    {
      "id": "buzzer_pwm",
      "name": "Buzzer-PWM",
      "type": 17,
      "enabled": false,
      "pins": [4],
      "params": {
        "pwmChannel": 1,
        "pwmFrequency": 2000,
        "pwmResolution": 8,
        "defaultDuty": 0
      }
    }
  ]
}

Note: The same pin can only be configured in one mode, choose either GPIO or PWM.

Peripheral Execution Linkage

Scenario 1: Periodic Alarm (Timer Trigger)

Function: Sound every 5 seconds, lasting 200ms

Web Interface Configuration Steps

Step 1: Create Rule

1. Click Peripheral Execution in the left menu
2. Click New Rule button
3. Fill in basic configuration:
   • Rule Name: Buzzer Periodic Alarm
   • Report Data: ❌ Disable
   • Enabled: ✅ Enable

Step 2: Configure Trigger

1. Click Add Trigger button

2. Fill in trigger configuration:

   Field	Value	Description
   Trigger Type	Select Timer Trigger	Execute at time intervals
   Timer Mode	Select Interval Timer	Execute every X seconds
   Interval Seconds	5	Execute every 5 seconds

Step 3: Configure Actions (3 actions needed)

Action 1: Start Buzzer

1. Click Add Action button
2. Fill in:
   • Action Type: Select HIGH Level
   • Target Peripheral: Select buzzer_gpio

Action 2: Delay 200ms

1. Click Add Action button again
2. Fill in:
   • Action Type: Select Command Script
   • Script Content: DELAY 200

Action 3: Stop Buzzer

1. Click Add Action button a third time

2. Fill in:

   • Action Type: Select LOW Level
   • Target Peripheral: Select buzzer_gpio

3. Click Save button

Execution Flow:

Every 5 seconds
  ↓
Start buzzer (HIGH)
  ↓
Delay 200ms
  ↓
Stop buzzer (LOW)

---

Scenario 2: PWM Tone Control (Platform Trigger)

Function: Control tone frequency via cloud platform commands

Web Interface Configuration Steps

Step 1: Create Rule

1. Click New Rule
2. Fill in basic configuration:
   • Rule Name: Buzzer Play Tone
   • Report Data: ✅ Enable
   • Enabled: ✅ Enable

Step 2: Configure Trigger

1. Click Add Trigger button

2. Fill in trigger configuration:

   Field	Value	Description
   Trigger Type	Select Platform Trigger	Receive cloud platform commands
   Operator	Select Match Pattern	Trigger when received data equals comparison value
   Comparison Value	{"freq":1000}	Command to match

Step 3: Configure Action

1. Click Add Action button

2. Fill in:

   • Action Type: Select Set PWM
   • Target Peripheral: Select buzzer_pwm
   • Action Params: {"duty":128,"frequency":1000}

3. Click Save button

Common Tone Frequencies

Note	Frequency (Hz)	Description
DO	523	Middle C
RE	587	D
MI	659	E
FA	698	F
SO	784	G
LA	880	A
SI	988	B
DO+	1046	High C

Notes

1. Active vs Passive: Active buzzers have a built-in oscillator, sound when powered; passive ones need PWM square wave
2. PWM Frequency Range: Human hearing range is 20Hz~20kHz, common alarm tones 1kHz~4kHz
3. Duty Cycle: Passive buzzers recommend 50% (duty=128/8bit), too low may not produce sound
4. Noise Control: Reduce duty cycle during debugging to lower volume