Example 37: Rotary Encoder

Experiment Overview

A rotary encoder generates two quadrature pulse signals (A/B phases) when rotated, enabling detection of rotation direction and angle. FastBee includes the built-in ENCODER peripheral type (type: 43) for rotary encoder support.

Hardware Wiring

Board Label	GPIO Pin	Connected Device
CLK (A)	GPIO34	Encoder A phase
DT (B)	GPIO35	Encoder B phase
SW	GPIO4	Encoder button (optional)

JSON Configuration Example

{
  "peripherals": [
    {
      "id": "encoder_01",
      "name": "Rotary Encoder",
      "type": 43,
      "enabled": false,
      "pins": [34, 35],
      "params": {}
    }
  ]
}

Peripheral Execution Linkage

Scenario: Encoder-Controlled LED Brightness (Polling Trigger + Script)

Feature: Rotate encoder to adjust LED brightness (PWM duty cycle)

Web UI Configuration Steps

Step 1: Ensure PWM LED Peripheral is Configured

• Peripheral ID: pwm_breath
• Type: GPIO PWM Output

Step 2: Create Rule

1. Click Peripheral Execution in the left menu
2. Click New Rule button
3. Fill in basic configuration:
   • Rule Name: Encoder Dimming
   • Report Data: ✅ Enabled
   • Enable: ✅ Enabled

Step 3: Configure Trigger (Polling Trigger)

1. Click Add Trigger button

2. Fill in trigger configuration:

   Field	Value	Description
   Trigger Type	Select Polling Trigger	Detect changes
   Target Peripheral	Select encoder_01	Rotary encoder
   Polling Interval	50	50ms (fast response)
   Condition Expression	changed == true	When value changes

Step 4: Configure Action (Script Conversion)

1. Click Add Action button

2. Fill in:

   • Action Type: Select Command Script
   • Action Parameter:

   var pos=encoderRead('encoder_01');
   var duty=Math.min(255,Math.max(0,pos*5));
   pwmWrite('pwm_breath',duty);

3. Click Save button

Rotary Encoder Value Reference

Rotation Direction	Count Value	Description
Forward (Clockwise)	Increment	A phase leads B phase
Reverse (Counter-clockwise)	Decrement	B phase leads A phase
Button Press	Separate detection	SW pin (GPIO4)

Notes

1. Interrupt-Driven: FastBee uses interrupts to detect encoder pulses, no steps lost
2. Direction Detection: A phase leading B phase = forward; B phase leading A phase = reverse
3. Debouncing: Mechanical encoders bounce; add 100nF capacitor in hardware or debounce in software
4. Count Range: Internal counter is int32, supports positive/negative counting
5. Pin Selection: Use interrupt-capable pins recommended