Apex Rover Hardware Programming

This repository contains the hardware programming files for the Apex Rover robot.

Folders

• ESP32: Central WiFi bridge. Receives commands from the mobile app via WebSocket and from the Raspberry Pi via HTTP, then routes them to the Mega or UNO over Serial.
• Mega_Movement_Control: Arduino Mega code for BTS7960 motor drivers, L298N linear actuator jacks, MPU6500 IMU, and ultrasonic sensors. Receives commands from ESP32 only. Pushes sensor data to the Raspberry Pi over USB Serial automatically.
• Uno_Arm_Control: Arduino UNO code for the camera stand (A4988 stepper + servo). Receive-only — no data is sent back.
• Raspberry: Raspberry Pi sensor relay. Reads sensor data pushed by the Mega over USB Serial and forwards it to the ESP32, which broadcasts it to the mobile app via WebSocket.

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Communication Flow

Command Flow (Mobile → Robot)

Mobile App
    │
    │  WebSocket (port 81)
    ▼
  ESP32
    ├──── Serial2 (TX GPIO17) ──────► Arduino Mega   (motors, jacks)
    └──── Serial1 (TX GPIO4)  ──────► Arduino UNO    (camera stand)

Sensor Flow (Robot → Mobile)

Arduino Mega
    │
    │  USB Serial (automatic push every 10s, or instantly on critical alert)
    ▼
Raspberry Pi
    │
    │  HTTP POST /sensor  (WiFi — Apex_Rover_Net)
    ▼
  ESP32
    │
    │  WebSocket broadcast
    ▼
Mobile App

Sensor Alert Types

Alert	Trigger
NONE	Normal periodic report
TILT_DANGER	Pitch > 30° or Roll > 25°
OBSTACLE_FRONT	Front ultrasonic < 10 cm
OBSTACLE_REAR	Rear ultrasonic < 8 cm

Sensor data format from Mega:

SENSOR:PITCH=2.30;ROLL=-1.10;UF=8.50;UR=9.20;ALERT=NONE

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Modes

Mode	Description
MANUAL	Default. Mobile app controls the robot. Raspberry Pi commands blocked.
AUTO	Reserved for future use.

Mode is switched by sending SYS:MODE:MANUAL or SYS:MODE:AUTO from the mobile app.

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Main Pins

ESP32

Pin	Connection
GPIO17 (TX)	Mega RX1 — Pin 19
GPIO4 (TX)	UNO D2 (SoftwareSerial RX)
GPIO16 (RX)	Mega TX1 — Pin 18 (not currently used)
GPIO15 (RX)	UNO D3 (not currently wired)
GND	Mega GND and UNO GND

Arduino Mega

Pin	Connection
RX1 — Pin 19	ESP32 GPIO17 TX (receives commands)
USB	Raspberry Pi (sends sensor data)
Pin 9	Right BTS7960 RPWM
Pin 11	Right BTS7960 LPWM
Pin 5	Left BTS7960 RPWM
Pin 7	Left BTS7960 LPWM
A8	Front Ultrasonic TRIG
A9	Front Ultrasonic ECHO
A11	Rear Ultrasonic TRIG
A12	Rear Ultrasonic ECHO
Pin 20 (SDA)	MPU6500 SDA
Pin 21 (SCL)	MPU6500 SCL
A0	Rear Jack L298N IN1
A1	Rear Jack L298N IN2
A3	Front Jack L298N IN3
A4	Front Jack L298N IN4

Arduino UNO

Pin	Connection
D2	ESP32 GPIO4 TX (SoftwareSerial RX — receives commands)
A0	Servo signal (camera tilt)
A1	A4988 EN
A2	A4988 DIR
D12	A4988 STEP

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Movement Commands (Mega via ESP32)

Command	Action
FORWARD	Move forward
BACKWARD	Move backward
LEFT	Turn left
RIGHT	Turn right
STOP	Stop motors and jacks
SPEED:N	Set speed (0–100%)
JACK:FRONT:EXTEND	Extend front jack
JACK:FRONT:RETRACT	Retract front jack
JACK:FRONT:STOP	Stop front jack
JACK:REAR:EXTEND	Extend rear jack
JACK:REAR:RETRACT	Retract rear jack
JACK:REAR:STOP	Stop rear jack
JACK:ALL:STOP	Stop all jacks
MODE:NORMAL	Normal driving mode
MODE:CLIMB	Stair climb mode
SYS:MODE:MANUAL	Switch system to MANUAL
SYS:MODE:AUTO	Switch system to AUTO

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Camera Stand Commands (UNO via ESP32)

Command	Action
CAM:LEFT	Rotate stepper left continuously
CAM:RIGHT	Rotate stepper right continuously
CAM:STOP	Stop stepper
CAM:STEP_LEFT:N	Move N steps left then stop
CAM:STEP_RIGHT:N	Move N steps right then stop
CAM:UP	Tilt servo up
CAM:DOWN	Tilt servo down
CAM:CENTER	Center servo and stop stepper
CAM:ZERO	Reset step position counter to 0
CAM:SPEED:N	Set step interval in microseconds (300–5000)

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Always-Allowed Commands

These commands are executed immediately regardless of mode or source:

SYS:MODE:MANUAL · SYS:MODE:AUTO · STOP · ESTOP · CMD:STOP · JACK:FRONT:STOP · JACK:REAR:STOP · JACK:ALL:STOP · JACK:STOP · CAM:STOP · ARM:BASE:STOP

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WiFi

Setting	Value
SSID	Apex_Rover_Net
Password	12345678
ESP32 AP IP	192.168.4.1
WebSocket	ws://192.168.4.1:81
HTTP	http://192.168.4.1

ESP32 HTTP Endpoints

Method	Endpoint	Description
GET	/	Status check
GET	/get_status	Returns current mode as JSON
POST	/command?cmd=...	Send always-allowed commands from Pi
POST	/sensor?data=...	Pi forwards Mega sensor data
GET	/get_last_sensor	Poll latest sensor reading