Dual BTS7960 Motor Controller

ESP32-based differential drive robot controller with web interface, using two BTS7960 dual H-bridge drivers with current sensing and stall protection.

Features

• Web-based dual motor control panel with real-time current monitoring
• Independent Forward/Reverse/Stop control for each motor with speed sliders (20-100%)
• Current sensing on both H-bridge sides for each motor
• Sample-based stall detection with automatic motor shutoff (per motor)
• ADC offset calibration at startup for accurate current readings
• Stall warning displayed on web interface per motor
• Emergency stop for both motors

Hardware

Components

Component	Model/Specification
Microcontroller	ESP32 LOLIN32 Rev1
Motor Drivers	2× BTS7960 Dual H-Bridge Module
Power Supply	12V DC
Sense Resistors	4× 1kΩ (for current sensing)

BTS7960 Module Reference

• DeepBlue Embedded Guide
• BTN7960 Datasheet

Wiring

Pin Assignments

Both drivers share enable pins (they enable/disable together).

Function	Motor 1	Motor 2	Notes
R_EN	GPIO 27	GPIO 27 (shared)	Both drivers enable together
L_EN	GPIO 14	GPIO 14 (shared)	Both drivers enable together
RPWM	GPIO 25	GPIO 32	Forward PWM
LPWM	GPIO 26	GPIO 33	Reverse PWM
R_IS	GPIO 34	GPIO 36 (VP)	Current sense - input only
L_IS	GPIO 35	GPIO 39 (VN)	Current sense - input only

Wiring Diagram

ESP32 LOLIN32          BTS7960 #1         BTS7960 #2
--------------         ----------         ----------
GPIO 27 (R_EN) ------> R_EN -----------> R_EN
GPIO 14 (L_EN) ------> L_EN -----------> L_EN

GPIO 25 (RPWM) ------> RPWM
GPIO 26 (LPWM) ------> LPWM
GPIO 34 (R_IS) <------ R_IS
GPIO 35 (L_IS) <------ L_IS

GPIO 32 (RPWM) --------------------> RPWM
GPIO 33 (LPWM) --------------------> LPWM
GPIO 36 (R_IS) <-------------------- R_IS
GPIO 39 (L_IS) <-------------------- L_IS

Current Sensing Circuit

The BTS7960 has IS (Current Sense) pins that output current proportional to motor load. A resistor converts this to voltage for ESP32 ADC.

BTS7960 Module                    ESP32
┌─────────────────┐              ┌──────┐
│  R_IS (pin 7)  ─┼──────┬───────┤GPIOxx│  (34 for M1, 36 for M2)
│                 │     [R]      │      │
│                 │     1kΩ      │      │
│  GND           ─┼──────┴───────┤GND   │
│                 │              │      │
│  L_IS (pin 8)  ─┼──────┬───────┤GPIOxx│  (35 for M1, 39 for M2)
│                 │     [R]      │      │
│                 │     1kΩ      │      │
│  GND           ─┼──────┴───────┤GND   │
└─────────────────┘              └──────┘

Note: GPIO34, 35, 36, 39 are input-only pins on ESP32, ideal for ADC readings.

Current Sensing Math

Parameter	Value	Formula
Sense Ratio	8500:1	I_sense = I_motor / 8500
Sense Resistor	1kΩ	V_sense = I_sense × R
At 4A motor current	0.47V	(4 / 8500) × 1000
Max readable current	28A	(3.3V × 8500) / 1000

Configuration

Key settings in include/config.h:

Setting	Default	Description
STALL_THRESHOLD	8.0A	Current threshold for stall detection
STALL_CONFIRM_SAMPLES	3	Number of consecutive samples to confirm stall (~300ms)
STALL_STABILIZE_MS	500ms	Ignore current spikes after direction change
PWM_FREQ	20kHz	PWM frequency (reduces motor noise)
MIN_PWM_PERCENT	20%	Minimum PWM when motor is running
CURRENT_LOG_INTERVAL_MS	100ms	Current sampling/logging interval
CURRENT_SENSING_ENABLED	true	Enable/disable in src/motor.cpp

Network

Setting	Value
WiFi SSID	tami
Static IP	10.81.2.185
HTTP Port	80

Build & Upload

pio run              # Build
pio run -t upload    # Build and upload
pio device monitor   # Serial monitor (115200 baud)

Web Interface

Access the control panel at http://10.81.2.185 (or the IP shown on serial monitor).

Features

• Dual Motor Panels: Side-by-side controls for Motor 1 (Left) and Motor 2 (Right)
• Current Display: Real-time forward (FWD) and reverse (REV) current readings per motor
• Direction Status: Shows FORWARD, REVERSE, or STOPPED per motor
• Speed Sliders: Adjustable from 20% to 100% per motor
• Stall Warning: Red banner per motor when stall is detected
• Emergency Stop: Global button to stop both motors immediately

API Endpoints

Endpoint	Method	Parameters	Description
/	GET	-	Control panel HTML page
/status	GET	-	JSON with both motors' status
/motor1/speed	GET	value (0-100)	Set motor 1 speed percentage
/motor1/direction	GET	value (-1, 0, 1)	Set motor 1 direction
/motor1/stop	GET	-	Stop motor 1
/motor2/speed	GET	value (0-100)	Set motor 2 speed percentage
/motor2/direction	GET	value (-1, 0, 1)	Set motor 2 direction
/motor2/stop	GET	-	Stop motor 2
/stop	GET	-	Emergency stop (both motors)
/speed	GET	value	Legacy: maps to motor1
/direction	GET	value	Legacy: maps to motor1

Status JSON Format

{
  "motor1": {
    "speed": 50,
    "direction": 1,
    "currentR": 2.35,
    "currentL": 0.00,
    "stalled": false
  },
  "motor2": {
    "speed": 50,
    "direction": -1,
    "currentR": 0.00,
    "currentL": 1.87,
    "stalled": false
  }
}

Stall Protection

The stall detection uses a sample-based approach for reliability (independent per motor):

1. Threshold: Current above 8.0A indicates potential stall (based on observed ~2A running vs ~17A stalled)
2. Debounce: 3 consecutive samples above threshold confirms stall (~300ms at 100ms intervals)
3. Stabilization: Ignores current spikes for 500ms after direction changes

When stall is confirmed on a motor:

1. That motor stops immediately
2. Serial log: MotorX STALL DETECTED! Current=X.XXA (threshold=8.0A)
3. Web interface shows red "STALL!" warning on that motor's panel

To resume operation, send a new direction command via the web interface.