WijiBoard Wiring Diagram

This document outlines the hardware connections for the WijiBoard.

Hardware Components

Microcontroller: Tenstar Robot ESP32-C3 Super Mini
Motors: 2× 28BYJ-48 (5V Stepper Motors)
Motor Drivers: 2× ULN2003 Driver Boards
Power System:
- 4S LiPo Battery
- XH-M609 Battery Low-Voltage Disconnect Module
- 2× Buck Regulators (step-down converters tuned to 5V)

Power Connections

The system is powered by a 4S LiPo battery. To protect the battery from over-discharge, it is connected to an XH-M609 module. The output of the XH-M609 is split into two separate Buck Regulators, both tuned to output 5V.

Buck Regulator 1 (MCU Power): Dedicated to powering the ESP32-C3 Super Mini.
Buck Regulator 2 (Motor Power): Dedicated to powering both ULN2003 driver boards to prevent voltage drops or electrical noise from affecting the MCU.

Important

Common Ground: You MUST connect the Ground (GND) from the ESP32 to the Ground (GND) of the ULN2003 drivers. Even though they have separate 5V power supplies, they need a common ground reference for the GPIO logic signals to work correctly.

Component	Connection	Destination
4S LiPo	`BAT+` / `BAT-`	XH-M609 `VIN+` / `VIN-`
XH-M609	`VOUT+` / `VOUT-`	Split to IN+ and IN- on both Buck Regulators
Buck 1 (MCU)	`OUT+ (5V)`	ESP32-C3 Super Mini `5V` (used as power input)
Buck 1 (MCU)	`OUT- (GND)`	ESP32-C3 Super Mini `GND`
Buck 2 (Motors)	`OUT+ (5V)`	ULN2003 (M1) `+ / 5V` and ULN2003 (M2) `+ / 5V`
Buck 2 (Motors)	`OUT- (GND)`	ULN2003 (M1) `- / GND` and ULN2003 (M2) `- / GND`
ESP32-C3 Super Mini	`GND`	Tie to the motor ground network (Common Ground)

Motor 1 (Right Motor) Logic

Physical Location: Right side (pivot at +12.9mm)

ESP32-C3 Super Mini Pin	ULN2003 (Motor 1) Pin
GPIO 0	`IN1`
GPIO 1	`IN2`
GPIO 3	`IN3`
GPIO 4	`IN4`

Motor 2 (Left Motor) Logic

Physical Location: Left side (pivot at -12.9mm)

ESP32-C3 Super Mini Pin	ULN2003 (Motor 2) Pin
GPIO 5	`IN1`
GPIO 6	`IN2`
GPIO 7	`IN3`
GPIO 10	`IN4`

Stepper to Driver Connections

Simply plug the white 5-pin JST connectors from the 28BYJ-48 motors into the corresponding white sockets on their respective ULN2003 driver boards. The connector is keyed and only fits one way.

Alternative Board Pinouts

The project supports multiple ESP32 variants. The main tables above show the default ESP32-C3 Super Mini. If you are using a different board, follow these logic connections:

ESP32-S3 (e.g. DevKitC)

Motor	IN1	IN2	IN3	IN4
Motor 1 (Right)	GPIO 4	GPIO 5	GPIO 6	GPIO 7
Motor 2 (Left)	GPIO 15	GPIO 16	GPIO 17	GPIO 18

ESP32-WROOM (e.g. NodeMCU / DevKit V1)

Motor	IN1	IN2	IN3	IN4
Motor 1 (Right)	GPIO 13	GPIO 14	GPIO 27	GPIO 26
Motor 2 (Left)	GPIO 25	GPIO 33	GPIO 32	GPIO 23

Schematic Overview

flowchart LR
    subgraph Power Delivery
        BATT[4S LiPo Battery] -->|14.8V| XHM609[XH-M609 Protector]
        XHM609 -->|14.8V| BUCK1[Buck Regulator 1]
        XHM609 -->|14.8V| BUCK2[Buck Regulator 2]
    end

    BUCK1 -->|5V Power| ESP[ESP32-C3 Super Mini]
    BUCK2 -->|5V Power| M1_Driver[ULN2003 M1]
    BUCK2 -->|5V Power| M2_Driver[ULN2003 M2]
    
    %% Common Ground
    ESP -. Common Ground .- M1_Driver
    ESP -. Common Ground .- M2_Driver
    
    %% Logic Signals
    ESP -- Pins 0,1,3,4 --> M1_Driver
    ESP -- Pins 5,6,7,10 --> M2_Driver
    
    %% Motors
    M1_Driver == 5-wire cable ==> M1[Motor 1 - Right]
    M2_Driver == 5-wire cable ==> M2[Motor 2 - Left]

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