Example 7: DC Motor Control

Experiment Overview

Control the start/stop and direction of a DC motor via GPIO output combined with a motor driver module (e.g., L298N, L9110). ESP32 GPIO cannot directly drive a motor, a driver chip is needed to amplify the current.

Hardware Wiring

Board Label	GPIO Pin	Connected Device
IN1	GPIO15	L298N/L9110 Input 1 (forward)
IN2	GPIO2	L298N/L9110 Input 2 (reverse)
ENA	GPIO0	L298N Enable (PWM speed control)

L298N module requires external power (6-12V), logic power at 3.3V/5V.

JSON Configuration Example

{
  "peripherals": [
    {
      "id": "motor_in1",
      "name": "Motor-Forward",
      "type": 12,
      "enabled": false,
      "pins": [15],
      "params": { "initialState": 0 }
    },
    {
      "id": "motor_in2",
      "name": "Motor-Reverse",
      "type": 12,
      "enabled": false,
      "pins": [2],
      "params": { "initialState": 0 }
    },
    {
      "id": "motor_speed",
      "name": "Motor-Speed",
      "type": 17,
      "enabled": false,
      "pins": [0],
      "params": {
        "pwmChannel": 2,
        "pwmFrequency": 1000,
        "pwmResolution": 8,
        "defaultDuty": 0
      }
    }
  ]
}

Peripheral Execution Linkage

Scenario 1: Motor Forward (Platform Trigger)

Function: Control motor forward via cloud platform command, speed 200/255 (~78%)

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: Motor Forward
   • 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	Match command
   Comparison Value	{"cmd":"forward"}	Forward command

Step 3: Configure Actions (3 actions needed)

Action 1: Set forward direction

1. Click Add Action button
2. Fill in:
   • Action Type: Select HIGH Level
   • Target Peripheral: Select motor_in1

Action 2: Set reverse direction LOW

1. Click Add Action button again
2. Fill in:
   • Action Type: Select LOW Level
   • Target Peripheral: Select motor_in2

Action 3: Set PWM speed

1. Click Add Action button a third time

2. Fill in:

   • Action Type: Select Set PWM
   • Target Peripheral: Select motor_speed
   • Action Params: 200 (duty cycle, 0-255)

3. Click Save button

Execution Flow:

Receive forward command
  ↓
IN1 = HIGH (forward direction)
  ↓
IN2 = LOW
  ↓
ENA = 200/255 (78% speed)
  ↓
Motor runs forward

---

Scenario 2: Motor Stop (Platform Trigger)

Function: Stop motor via cloud platform command

Web Interface Configuration Steps

Step 1: Create Rule

1. Click New Rule
2. Fill in basic configuration:
   • Rule Name: Motor Stop
   • Report Data: ✅ Enable
   • Enabled: ✅ Enable

Step 2: Configure Trigger

1. Click Add Trigger button
2. Fill in:
   • Trigger Type: Select Platform Trigger
   • Operator: Select Match Pattern
   • Comparison Value: {"cmd":"stop"}

Step 3: Configure Actions (3 actions needed)

1. Action 1: LOW Level → motor_in1

2. Action 2: LOW Level → motor_in2

3. Action 3: Set PWM → motor_speed, param 0

4. Click Save button

Motor Control Truth Table

IN1	IN2	ENA(PWM)	State
HIGH	LOW	0-255	Forward (speed by PWM)
LOW	HIGH	0-255	Reverse (speed by PWM)
LOW	LOW	0	Coast stop
HIGH	HIGH	0-255	Brake (quick stop)

Notes

1. External Power: Motor needs independent power supply, do not power from ESP32's 3.3V
2. PWM Speed Control: Duty cycle 0~255 (8bit), higher value = faster speed
3. Brake Mode: IN1=IN2=1 for braking, IN1=IN2=0 for coast stop
4. Back EMF: Motor's reverse voltage at power-off may damage driver chip, ensure module has protection diodes
5. GPIO0: When used as ENA, pay attention to boot timing to avoid affecting ESP32 startup