MQTT ModularControllerBoard

MQTT Modular Controller Board

Currently In Testing - Not Yet Tested

ESP32-S3-WROOM-1U based motherboard designed to communicate externally via MQTT, and read sensors, control interfaces and other hardware through purpose built modules. For example, actuator control (pumps, solenoids, etc.), and water sensor readings etc.

Features

• ESP32-S3-WROOM-1U microcontroller with antenna support
• Four module slots using standardized 2x10 pin headers
• Power rails: 12 V, 5 V, and 3.3 V supplied to modules
• High-side reverse polarity protection on 12 V and 5 V inputs
• USB-powered operation for programming and testing (no 12 V required)
• Screw terminal power input
• 4-layer PCB designed for assembly (routing / GND / GND / routing)
• 4 x 3.5mm Mounting Holes

Architecture

Core Components

• Microcontroller: ESP32-S3-WROOM-1U
• Power Input: 12 V via screw terminals
• Power Conversion:
  • 12 V → 5 V using TPS563200DDCR (TI WEBENCH design)
  • 5 V → 3.3 V using LDO
• Maximum Outputs:
  • 12 V: Limited by external supply
  • 5 V: 3 A total (0.8 A used internally)
  • 3.3 V: 1 A total (0.6 A used by ESP32)

Module Interface

Each of the four modules connects via two 10-pin headers and receives:

• Power: 12 V (4 pins shared), 5 V (2 pins), 3.3 V (2 pins), GND (4 pins)
• Communication:
  • Shared SPI: CS(per module), MOSI(GPIO11), MISO(GPIO13), SCK(GPIO12)
  • Shared I²C: SDA(GPIO4), SCL(GPIO5)
• Control/Detection:
  • One general-purpose GPIO per module
  • One module detection/sense pin per module
  • Module-specific CS pins.

Module Slots (Left to Right)

Slot 1:

• General Purpose: GPIO1
• Module Detection: GPIO2
• CS Pin: GPIO16

Slot 2:

• General Purpose: GPIO43
• Module Detection: GPIO44
• CS Pin: GPIO15

Slot 3:

• General Purpose: GPIO42
• Module Detection: GPIO41
• CS Pin: GPIO7

Slot 4:

• General Purpose: GPIO40
• Module Detection: GPIO39
• CS Pin: GPIO6

Additional Features

• USB micro-B for programming and power (VBUS sense on GPIO08)
• Power indicator LED on 3.3 V rail
• EN button and RESET functionality
• Manual download mode: Hold BOOT button while pressing RESET, then release BOOT

PCB Stackup

4-layer board:
Component/Routing → Ground plane → Ground plane → Routing

Impedance Control: Designed for JLCPCB Impedance Control Stackup of JLC04161H-7628, Finished thickness of 1.59mm.

Setup and Build

Firmware: The PlatformIO firmware includes non-blocking WiFi station reconnection and a captive-portal setup flow. On first boot, the portal scans nearby networks and offers a selectable SSID list plus manual SSID entry.

Programming:

• Connect via USB micro-B.
• Use ESP32 flashing tools (esptool, Arduino IDE, ESP-IDF, etc.).
• For manual bootloader mode: Hold BOOT button, press RESET, release BOOT.

Module Development: Modules must conform to the 2x10 header pinout with 40mm pitch. Board uses 2 x 10, 8.5mm Female Headers (A2541HWV-10P). Recommended 3A support.

Repository Contents

• KiCad schematic and PCB files
• Project configuration
• Backups folder

License

This documentation is part of MQTT-ModularControllerBoard Project and is licensed under the CERN Open Hardware Licence Version 2 - Permissive (CERN-OHL-P-2.0). You may redistribute and modify this documentation under the terms of the CERN-OHL-P-2.0. This documentation is distributed WITHOUT ANY EXPRESS OR IMPLIED WARRANTY, INCLUDING OF MERCHANTABILITY, SATISFACTORY QUALITY AND FITNESS FOR A PARTICULAR PURPOSE. See the CERN-OHL-P-2.0 for applicable conditions.