🚗 ESP32 RC Car using ESP-NOW (Transmitter + Receiver)

A fully wireless RC-car system built using two ESP32 boards, two BTS7960 high-current motor drivers, and ESP-NOW for ultra-fast and low-latency communication.

This project supports:

✔ Analog joystick steering ✔ Potentiometer-based speed control ✔ Button input ✔ Differential motor control ✔ Automatic failsafe (motors stop if signal is lost) ✔ Expandable multi-channel design

---

🧩 Project Overview

This system has two ESP32 boards:

1️⃣ Transmitter ESP32

• Reads joystick X/Y
• Reads potentiometer (speed control)
• Reads joystick switch button
• Sends the values wirelessly to the receiver using ESP-NOW

2️⃣ Receiver ESP32

• Receives joystick data
• Processes differential drive (left/right motors)
• Controls two BTS7960 motor drivers
• Automatically stops motors if transmitter signal is lost

---

📦 Hardware Required

🔹 Transmitter Side

Component	Qty
ESP32 Dev Board	1
2-axis Joystick Module	1/2
Potentiometer (10k recommended)	1
Jumper wires	Several
5V power bank / Li-ion battery	1

---

🔹 Receiver / RC Car Side

Component	Qty
ESP32 Dev Board	1
BTS7960 Motor Driver	2 (Left + Right motor)
12V–24V battery for motors	1
DC motors (high torque)	2
Chassis + wheels	1 set
Jumper wires (thick wires for motors)	Several

---

🕹️ Transmitter Wiring

Joystick

Joystick Pin	ESP32 Pin
VRX	GPIO34
VRY	GPIO35
SW	GPIO32
+5V	3.3V/5V
GND	GND

Potentiometer

Pot Pin	ESP32 Pin
Middle Output	GPIO33
One Side	3.3V/5V
Other Side	GND

---

🚗 Receiver Wiring (BTS7960 + Motors)

Motor Driver 1 – LEFT Motor

BTS7960 Pin	ESP32 Pin
RPWM	GPIO25
LPWM	GPIO26
R_EN	GPIO27
L_EN	GPIO14

Motor Driver 2 – RIGHT Motor

BTS7960 Pin	ESP32 Pin
RPWM	GPIO12
LPWM	GPIO13
R_EN	GPIO15
L_EN	GPIO2

BTS7960 Power

• B+ → Motor Battery +
• B− → Motor Battery −
• Motor terminals → actual motor

⚠️ Never power motors from ESP32 5V — BTS takes a separate supply.

---

🛰️ ESP-NOW Pairing (IMPORTANT)

🟦 Step 1 — Get the Receiver’s MAC Address

Upload the receiver code first.

Open Serial Monitor → it prints:

Receiver MAC Address: 80:F3:DA:55:8C:48
COPY THIS MAC ADDRESS TO TRANSMITTER CODE!

🟦 Step 2 — Add MAC to Transmitter Code

In the transmitter code, replace:

uint8_t receiverMAC[] = {0x80, 0xF3, 0xDA, 0x55, 0x8C, 0x48};

with your own receiver’s MAC.

If this is wrong → transmitter will NOT connect.

---

📡 How the System Works

🕹️ Transmitter

• Reads joystick X/Y (0–4095)
• Converts to −100 … +100 range
• Reads potentiometer → 0–100 speedLevel
• Packs into a struct:

struct_message {
  int xAxis;
  int yAxis;
  int speedLevel;
  bool button;
};

• Sends to receiver via ESP-NOW every 50ms

🚗 Receiver

• Gets the struct and extracts X/Y/speed values

• Calculates:

  • Forward/backward speed (Y axis)
  • Left/right steering adjustment (X axis)

• Uses differential drive:

  • Left motor speed adjusted opposite of right motor

• Speed converted to PWM (0–255)

• Controls motors through BTS7960 PWMs

• Timeout protection stops motors if no signal for 1 sec

---

📡 Transmitter Code Explanation

1. Reads Joystick + Pot

int rawX = analogRead(JOYSTICK_X_PIN);
int rawY = analogRead(JOYSTICK_Y_PIN);
int rawP = analogRead(POT_PIN);

2. Convert joystick raw values to a usable −100 to +100 range

x = map(rawX, 0, 4095, -100, 100);

3. Apply deadzone

Removes jitter around the center.

4. Send Data via ESP-NOW

esp_now_send(receiverMAC, (uint8_t*)&myData, sizeof(myData));

---

🚗 Receiver Code Explanation

1. ESP-NOW receive callback

Triggered every time transmitter sends data.

void OnDataRecv(...)  
{
  memcpy(&incomingData, incomingDataByte, sizeof(incomingData));
  controlMotors(...);
}

2. Differential drive calculation

leftMotorSpeed = map(yAxis, -100, 100, -baseSpeed, baseSpeed);
rightMotorSpeed = map(yAxis, -100, 100, -baseSpeed, baseSpeed);

3. Steering adjustments

if (xAxis < 0) { turn left }
if (xAxis > 0) { turn right }

4. Apply to BTS7960

Forward:

analogWrite(RPWM, speed);
analogWrite(LPWM, 0);

Backward:

analogWrite(LPWM, speed);
analogWrite(RPWM, 0);

5. Signal loss protection

If no packet is received for 1 second → motors stop.

---

🚀 Future Improvements

Here are things you can add later (easy upgrades):

🔹 1. Extra Channels

• Add headlights using LED
• Horn/buzzer
• Servo for camera pan/tilt
• Extra buttons for custom features

Just expand the struct:

int extra1;
int extra2;
bool sw2;

🔹 2. FPV Camera System

Add ESP32-CAM or analog FPV system.

🔹 3. OLED Display on Transmitter

• Show speed
• Battery status
• Signal strength

🔹 4. Telemetry Return Channel

Receiver → Transmitter Send:

• Battery voltage
• Motor temperature
• Distance sensor values

🔹 5. Add PID Motor Control

Smoothen movement and avoid jerkiness.

---

🧪 Testing Tips

• Always test motors with wheels lifted first
• Expect the joystick Y-axis to control forward/back
• X-axis controls left/right turning
• Potentiometer smoothens speed