The ESP32 has become a popular choice for IoT and automation development. With built-in Wi-Fi and flexible programming options, it can connect sensors, monitor operating conditions, and control external equipment.

However, many practical projects require more than basic GPIO pins. They may need analog current and voltage inputs, analog outputs, temperature sensors, relay channels, and RS485 communication.

The Eletechsup ES32G15 combines these interfaces in one expansion board for a compatible 38-pin ESP32-DevKitC. It provides a practical hardware platform for developers who want to build customized smart home controllers, remote monitoring systems, and PLC-style automation applications.

Product page: https://eletechsup.com/products/es32g15-esp32-devkitc-smart-home-expansion-board-ntc

1. Connecting ES32G15 to the Open-Source ESP32 Ecosystem

Open-source software makes it easier for developers to build on existing projects rather than starting from scratch.

One relevant example is the GitHub repository below:

GitHub project: https://github.com/makstech/esphome-es32a08-expansion-board-example

This project demonstrates how ESPHome can be configured for the Eletechsup ES32A08 expansion board, including digital inputs, relay outputs, and analog input functions.

Although the repository targets the ES32A08 rather than the ES32G15, it illustrates a useful development approach: define the board's hardware interfaces in ESPHome, expose suitable functions to a home automation platform, and build application-specific logic around them.

The ES32G15 has a different I/O configuration, so its pin assignments, hardware drivers, and firmware configuration must be developed or adapted and tested separately. The ES32A08 repository should be treated as a reference for the general workflow, not as a ready-to-use ES32G15 configuration.

For developers familiar with ESPHome, Arduino, or ESP-IDF, this provides a clear starting point for exploring their own ES32G15 applications.

2. What Can the ES32G15 Do?

The ES32G15 integrates multiple types of I/O on one board:

• 2-channel 0/4–20 mA current input

• 2-channel 0–5 V / 0–10 V voltage input

• 2-channel 0/4–20 mA current output

• 2-channel 0–5 V / 0–10 V voltage output

• 4-channel NTC temperature input for compatible 10 kΩ thermistors

• 4-channel NPN digital input

• 4-channel relay output

• 1 RS485 interface

• 5 additional GPIO ports

The board supports a DC 12–28 V supply and measures approximately 121 × 72 × 19 mm without the enclosure.

A compatible 38-pin ESP32-DevKitC board is required. The expansion board does not operate independently.

3. Application Example: Wi-Fi Remote Switching

One possible project is a Wi-Fi-based remote switching system.

The ESP32 can connect to a local network and receive commands from custom firmware, a web interface, or an appropriately configured home automation system.

A typical workflow might look like this:

1. A user selects a device in a dashboard.

2. The ESP32 receives the command over Wi-Fi.

3. The firmware checks the requested operation.

4. The corresponding relay output switches the connected load.

5. The system updates its status through the configured software interface.

Developers could extend this design with MQTT messaging or HTTP-based control.

For Home Assistant integration, the software configuration must define the board's actual pin mapping and relay behavior. A compatible ESPHome configuration for ES32G15 should be developed and tested rather than copied directly from an ES32A08 project.

4. Application Example: Temperature Monitoring and Automatic Ventilation

The four NTC inputs allow developers to create projects that monitor temperatures at several locations.

For example, compatible thermistors could be placed inside an equipment cabinet, near a ventilation outlet, or in different zones of a room.

The ESP32 firmware can read the sensors, convert their measurements into temperature values, and compare the results against configured thresholds.

A simple control strategy could be:

• If the temperature rises above the upper threshold, turn on ventilation.

• Keep ventilation running while the temperature remains high.

• Turn it off when the temperature falls below a lower threshold.

• Send the temperature readings to a dashboard for monitoring.

This approach can be extended with schedules, alerts, data logging, or remote status reporting.

The accuracy of the readings depends on the thermistors, their B-value parameters, calibration, and the measurement circuit. Appropriate testing is required before using the system for temperature-sensitive equipment.

5. Application Example: Analog Sensor Monitoring

Many industrial sensors provide voltage or current signals instead of digital outputs.

The ES32G15's analog inputs make it suitable for developing monitoring applications around compatible 0–10 V, 0–5 V, and 4–20 mA signals.

Potential applications include:

• Monitoring a compatible pressure transmitter.

• Reading an analog process signal.

• Measuring a sensor output and displaying the calculated value.

• Sending measurements to an MQTT broker or monitoring dashboard.

For example, a compatible 4–20 mA transmitter can represent a configured process range. The firmware can convert the measured current into an engineering value and publish the result for remote monitoring.

The two analog output channels can also be used to generate compatible voltage or current control signals, subject to the board's channel configuration and electrical specifications.

Before connecting external equipment, verify the signal range, wiring, polarity, and the requirements of the receiving device. Select the correct operating mode using the board's documentation.

6. Application Example: Combining Wi-Fi and RS485

Wi-Fi is convenient for network access, while RS485 is widely used to connect compatible devices in automation systems.

The ES32G15 includes both interfaces, allowing developers to build a system that combines local I/O with network connectivity.

For example, a prototype could:

• Acquire local temperature and analog sensor measurements.

• Read digital input signals.

• Control local relay outputs.

• Communicate with an external RS485 device.

• Publish selected operating data over Wi-Fi.

With suitable firmware, MQTT can be used to exchange data with a broker, while a compatible serial protocol can be implemented for RS485 communication.

RS485 itself defines the electrical interface rather than the complete application protocol. If Modbus RTU is required, the firmware must implement the correct protocol and device settings, including baud rate, parity, addressing, and message handling.

7. Can ES32G15 Be Used as a Simple PLC?

The ES32G15 can serve as the hardware foundation for a simple PLC-style controller.

Developers can combine input monitoring, analog measurements, temperature readings, relay switching, and communication into a custom control program.

A typical control cycle might be:

1. Read digital and analog inputs.

2. Calculate temperature or process values.

3. Evaluate programmed conditions.

4. Update relay and analog outputs.

5. Send status information to a monitoring system.

Unlike a ready-to-run PLC, the ES32G15 requires a compatible ESP32 controller and application firmware. Developers should also implement suitable error handling, startup behavior, watchdog recovery, and electrical protection for their intended use.

8. A Practical Development Path

For developers starting an ES32G15 project, the following sequence is recommended:

Step 1 — Verify the hardware. Install a compatible 38-pin ESP32-DevKitC and supply the board with the specified DC voltage.

Step 2 — Test each interface. Begin with one digital input or relay output, then test NTC readings, analog inputs, analog outputs, and RS485 communication individually.

Step 3 — Choose a software framework. Arduino and ESP-IDF are options for custom firmware. ESPHome may also be considered when the required hardware interfaces can be configured and tested successfully.

Step 4 — Add network integration. Implement the desired web interface, MQTT communication, or Home Assistant integration.

Step 5 — Validate the complete application. Test normal operation, power cycling, communication failures, and safe output states before connecting the system to real equipment.

Conclusion

The Eletechsup ES32G15 combines ESP32 programmability with temperature inputs, analog current and voltage I/O, digital inputs, relay outputs, and RS485 communication.

Its hardware makes it a useful foundation for developers working on Wi-Fi monitoring, smart home control, sensor acquisition, and compact PLC-style automation.

Open-source projects such as the ESPHome example for the ES32A08 show how ESP32 expansion hardware can be integrated into a broader home automation ecosystem. While that repository does not directly support the ES32G15, it provides a reference for developers who want to build and validate their own configuration.

Explore the Eletechsup ES32G15:

https://eletechsup.com/products/es32g15-esp32-devkitc-smart-home-expansion-board-ntc

Related GitHub reference:

https://github.com/makstech/esphome-es32a08-expansion-board-example

The GitHub repository is an independent community project for the ES32A08, not an official ES32G15 integration. ES32G15 software configurations and application functions must be developed or adapted and verified for the actual hardware.