BRAIN_BOARD

Custom STM32H753 main controller board for modular motion, control, storage, communication, and daughter-board expansion.

BRAIN_BOARD is the clean logic/control board in a modular hardware system. It handles MCU control, communication, debugging/programming, storage, sensor inputs, and daughter-board interfaces. Noisy motor power and phase switching are kept on external boards such as DIRTY_MTR_BOARD.

Project Status

In progress. Main controller schematic and PCB layout under development/review.

System Role

Host / USB / RS485 / CAN
        ↓
BRAIN_BOARD
        ↓ STEP / DIR / SPI / GPIO
DIRTY_MTR_BOARD / daughter boards
        ↓
Motor / sensors / external hardware

BRAIN_BOARD does not directly drive stepper motor coils. Motor current, switching, and noisy power handling belong on dedicated daughter boards.

Key Specs

Item	Value
MCU	STM32H753ZITx
Package	LQFP-144
Logic rail	+3.3V
USB	USB-C
External communication	RS485, CAN
Storage	microSD
Nonvolatile memory	SPI FRAM
Debug/programming	SWD / debug UART headers
Daughter-board support	Motor/control, analog I/O, manual jog, external flags
Power options	USB or VIN path with jumper selection
Board role	Main controller / system brain

Main Features

• STM32H753 main MCU
• USB-C connector for USB data/power path
• USB VBUS fused input
• VIN input path
• Jumper-selectable power source
• +3.3V regulation and local decoupling
• RS485 transceiver interface
• CAN interface connector
• SPI FRAM
• microSD card interface
• SWD programming/debug header
• Debug UART header
• User switch
• Boot button
• Reset button
• Status LEDs
• Analog input header
• Daughter-board connectors
• Motor-control signals routed to external motor driver board
• Active-low home/crash/manual-jog style inputs
• Labeled test points and silkscreen notes

Power Architecture

BRAIN_BOARD is intended to keep logic power clean and separate from noisy motor power.

USB-C / VIN input path
        ↓
power selection / protection
        ↓
+3.3V logic rail
        ↓
STM32H753 + memory + communication interfaces

Motor power is not generated or switched directly on BRAIN_BOARD.

Daughter-Board Strategy

Planned or related daughter boards include:

• DIRTY_MTR_BOARD for motor driving and noisy power handling
• DUMB_MANUAL_MTR_BOARD for external manual jog buttons
• Sensor / analog input boards
• Communication or debug helper boards

Manual jog style inputs are intended to be active-low. External buttons pull the signal to GND when pressed.

PCB Notes

Design priorities:

• Keep MCU decoupling tight and local
• Keep the ground system solid and low impedance
• Route communication interfaces cleanly
• Keep noisy motor-driver current off the main controller board
• Use clear connector labels and test points
• Preserve clean SWD/debug access

Repository Output Images

Expected image paths for GitHub README rendering:

Outputs/
  IMG/
    3D-T.png
    3D-B.png
    SCHEMATIC.png
    L1-SIG.png
    L2-3V3.png
    L3-GND.png
    L4-MIX.png

Safety / Design Note

BRAIN_BOARD is a low-voltage controller PCB. Motor power, external loads, and high-current switching should be handled on separate boards with appropriate power routing, protection, and review.