Imported from GitHub: varunsaireddyv/modular-esp32-sensor-hub- · commit 8036d93 · license MIT

Description

Lightweight, deployable embedded sensor hub built on ESP32. With hot-swappable sensor ports, on site SD card logging.

README

modular-esp32-sensor-hub-

Introduction:

This project is a modular ESP32-based sensor hub designed for rapid prototyping and monitoring environements. It supports a wide range of sensors through hot-swappable connectors, with onboard SD card logging, and runs off a 5v li-ion battery. The goal is to offer a deployable, plug-and-play embedded system that’s both scalable and user-friendly.

Primary Design Goals:

Modularity:hot-swappable sensor ports for analog, digital, and I2C devices, swapable power source, programable ESP board

Deployability:standalone and swapable power and onboard storage, light weight custom ESP 32 WROOM 32D board

Plug-and-play:Firmware pre installed and no user input required exept for conecting sensors to premaped sensor pins

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Features

• ESP32-WROOM-32D core (Wi-Fi + BLE)
• 13 modular sensor ports: digital, analog, and I2C
• MicroSD card support (SPI) for data logging
• 0.96" OLED screen support via I2C
• Shared I2C bus (GPIO21/GPIO22) with pull-up planning
• Dual voltage rails: 5V (VBUS) and 3.3V (via AMS1117 regulator)
• USB or Li-ion battery input with diode-based auto-switching
• Ground stitched bottom layer with dedicated signal routing on top
• Wide traces (1mm) for power, separate analog and digital zones
• Modular firmware (coming soon)

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Pin Mapping

Function	GPIO Pin
I2C SDA	GPIO21
I2C SCL	GPIO22
SD Card CS	GPIO5
SD Card CLK	GPIO18
SD Card MOSI	GPIO23
SD Card MISO	GPIO19
Analog Sensor 1	GPIO32
Analog Sensor 2	GPIO33
Digital Sensor 1	GPIO25
Digital Sensor 2	GPIO26
Digital Sensor 3	GPIO27
Digital Sensor 4	GPIO14
Digital Sensor 5	GPIO12
Digital Sensor 6	GPIO13
OLED (I2C)	Shared
I2C Misc Ports 1-2	Shared

All analog lines use 1k/2k voltage dividers to drop from 5V to 3.3V safe levels for the ESP32. All sensors are routed through XH-3P connectors with GND, VCC, and Signal/I2C.

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Supported Sensors(Default in Firmware)

Analog / Digital Sensors

• MQ135 (Air Quality)
• DHT22 (Temp & Humidity)
• Raindrop Sensor
• Sound Sensor (x2)
• Soil Moisture
• LDR (Light)
• IR Receiver

I2C Sensors & Modules

• MPU6050 (Accel + Gyro)
• BME280 (Temp + Pressure + Humidity)
• BH1750 (Light)
• OLED Display

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Included Files/Folders

• Schematic: ESP32_WROOM_D.kicad_sch
• Board Layout: PCB_main.kicad_pcb
• Schematic PNG preview: Schemtaic.png
• 3D render: PCB.png
• 3D render front: PCB_F.png
• 3D render back: PCB_B.png
• License: MIT
• Firmware: src/, include/, lib/, "platform.ini"
• Documents: "ERC", "DRC", "Datasheet", "Pin_mapping"

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Firmware flow

main.cpp : -Calls SensorManager.begin() → initializes I2C, sets up pins -Calls SensorManager.detectConnectedSensors() → auto-detects attached sensors -Calls SensorManager.readAll() repeatedly inside loop() to read & print sensor data

sensormanger.cpp/.h : -Defines bool flags for each supported sensor -Each sensor has its own analogRead() or I2C detection logic -readAll() only reads sensors that were marked as detected(bool=true)

pins.h : -Central place to edit pin numbers (for future boards or remapping) -Also includes notes on analog/digital/I2C mappings

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Adding own sensors

You can plug in any new sensor to unused analog/digital/I2C ports. Here’s how to support it in firmware:

Step 1 : Wiring :

-Connect the sensor to a free port (check Pin Mapping table) -Use correct GND/VCC/SIG (XH-3P)

step 2 : Modify "sensormanger.h" :

-Add a flag for presence detection :

extern bool NEW_SENSOR_present;

step 3 : Modify "pins.h" :

-define your sensor with its GIO pin :

#define NEW_SENSOR_PIN ##   //replace ## with GIO pin(can be found in sensor data sheet)

step 4 : Modify "sensormanger.cpp" :

-In detectConnectedSensors add :

-if (analogRead(NEW_SENSOR_PIN) > 50) NEW_SENSOR_present = true;   //(for analog sensors)
-if (analogRead(NEW_SENSOR_PIN) > 50) NEW_SENSOR_present = true;   //(for digital sensors)
-Check sensor library for I2C (differs from sensor to sensor reffer sesnormanager.cpp for refrence)

-In readAll add :

-if (NEW_SENSOR_present) {
  int val = analogRead(NEW_SENSOR_PIN);   //(for analog)
  }
-if (NEW_SENSOR_present) {
  int val = digitalRead(NEW_SENSOR_PIN);   //(for analog)
    }
  -Check sensor library for I2C (differs from sensor to sensor reffer sesnormanager.cpp for refrence)


  

step 5 : SD card logging

-5.1 : Update sdlogger.h :

-In sdlogger.h, go to the writeRow() function declaration. Add your new sensor’s argument at the end:

void writeRow(
    String timestamp,
    ...
    String BH1750,
    String NEW_SENSOR      //<-- Add this
) ;

5.2 : Update sdlogger.cpp :

-Update the writeRow() definition: -Add the new parameter to the function like:

void writeRow(
    String timestamp,
    ...
    String BH1750,
    String NEW_SENSOR       //<-- Add here too
) {

-Add it to the file write block: -Scroll to where values are written into the file. Append this:

file.print(NEW_SENSOR); file.println();    //<-- Just before file.close();

-Update the CSV header: -Only needed once, in the same file (inside if (!SD.exists("/logs.csv"))):

file.println("Time stamp,MQ135-D,MQ135-A,DHT22,RAIN-A,RAIN-D,SOUND-A,SOUND-D,SOIL-A,SOIL-D,MPU6050,BMP180,BH1750,NEW_SENSOR");

5.3 : Modify readAll() in SensorManager : -If your sensor is optional/detectable:

String newSensorValue = "NA";
if (NEW_SENSOR_present) {
  int val = analogRead(NEW_SENSOR_PIN);  // or digitalRead / I2C
  newSensorValue = String(val);

-Then pass it to the logger:

SdLogger::writeRow(
  timestamp,
  mq135_d, mq135_a,
  dht22,
  rain_a, rain_d,
  sound_a, sound_d,
  soil_a, soil_d,
  mpu6050,
  bmp180,
  bh1750,
  newSensorValue       //<-- Final argument
);
}

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Flashing the Board (PlatformIO)

To upload firmware to the ESP32 board:

1. Install PlatformIO:

   -VSCode + PlatformIO extension -Or via CLI: https://platformio.org/install/cli

2. Clone this repo:

   -git clone https://github.com/varunsaireddyv/modular-esp32-sensor-hub-.git -cd modular-esp32-sensor-hub-

3. Plug in the board via USB

4. Build and upload -pio run --target upload

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Hardware Design Notes

• 2-layer PCB: Top for signals, Bottom for full GND plane
• GND stitching via multiple vias across zones
• AMS1117 regulator outputs 3.3V rail, with thick trace routing
• Diode-logic used to auto-select between USB or battery power
• All connectors: XH-3P format for modularity
• I2C pull-up resistors placed close to MCU

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License

This project is licensed under the MIT License. See LICENSE file for full terms. You may freely modify, distribute, or use this project in your own designs.

For hire !!

reach out at : [email protected]