README.md


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# HsMouse Quad A4988 Motor Controller HAT

> **Warning**: This project is not intended for production use.
> It is a learning exercise for KiCad and PCB design fundamentals.

![quad-a4988-rev2-front.png](quad-a4988-rev2-front.png)
![quad-a4988-rev2-back.png](quad-a4988-rev2-back.png)

## Overview

This Raspberry Pi 5 HAT features four A4988 stepper motor driver chips,
designed to control four NEMA stepper motors. The primary application is a small robotic car using
[Mecanum wheels](https://eu.robotshop.com/products/60mm-mecanum-wheel-set-2x-left-2x-right)
for omnidirectional movement.

## Features
- **Motor Control**: Four A4988SETT-R drivers for independent control of NEMA stepper motors.
    - Shared GPIO connections for common pins (e.g., `MSx`, `ROSC`, `~ENABLE`)
      to simplify control logic.
    - Assumes synchronized wheel speeds when enabled.
- **Precision Voltage Reference**: ISL21080 provides a stable 0.9V reference
  to all A4988 `VREF` pins, limiting motor coil current to **1.125A**.
- **Directional Logic**: SN74LVC2G08DCUR dual AND gate enables diagonal wheel movement
  by selectively disabling `STEP` signals (see movement table below).

![wheel-rotations.png](wheel-rotations.png)