LoRa-Based Remote Environmental Monitoring System (DHT11 & MAX32672)
Introduction
This project showcases an ultra-low-power, long-range remote environmental monitoring node. Built using the highly secure and efficient Analog Devices MAX32672FTHR evaluation board, the system samples real-time temperature and humidity data from a DHT11 sensor and wirelessly broadcasts it using an SX1278 LoRa module.
The data is picked up by a custom-built ESP32-based LoRa gateway, which aggregates the information and securely pushes it to a database for remote tracking and visualization.
Event Recognition I am proud to share that I received the MAX32672FTHR development board as part of the “Learn, Build & Win” event organized by DigiKey and Circuit Digest. This project is a direct result of that amazing initiative, designed to explore the low-power and processing capabilities of this specialized hardware!
The Hardware: About the MAX32672FTHR Board
The MAX32672 is an ultra-low-power microcontroller featuring an Arm® Cortex®-M4 processor with a Floating Point Unit (FPU). It is optimized for battery-powered medical sensors, industrial IoT, and edge-computing applications.
Key Board Features Used in This Project:
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Flexible SPI Framework: Leveraged MXC_SPI1 running standard 8-bit mode at 1 MHz to flawlessly interface with the SX1278 LoRa module.
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Granular GPIO Control: Utilized low-level register manipulation (outen_set / outen_clr) on port P0.6 to handle the tight microsecond timing required by the DHT11’s 1-wire protocol.
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Power Efficiency: Designed with the board’s low-power profiles in mind, making it an excellent candidate for field-deployed, battery-operated sensor nodes.
System Architecture & Connectivity
The project is split into two primary components: the Sensor Node and the Gateway.
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The Transmitter Node: The MAX32672FTHR reads the DHT11 data line, processes the raw 40-bit packet, validates it via a checksum byte, and formats it into a payload string (e.g., H:45% T:27C). It then structures an SPI request to push this payload over the air via the 433 MHz SX1278 module.
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The Receiver Gateway: An ultra-compact ESP32 (or Arduino Pro Mini framework) paired with a companion SX1278 module acts as the listener. Once a packet is parsed, the gateway translates the payload and pushes it instantly to a centralized database.
Media & Gallery
1. Unboxing and Hardware Setup
Pristine hardware courtesy of DigiKey and Circuit Digest’s Learn, Build & Win event.
2. The ESP32 Data Gateway
The ESP32 LoRa Gateway responsible for gathering the node’s transmissions and uploading them to the database.
3. Results
Code Repository & Firmware Overview
The firmware is built using the official Analog Devices MSDK using a customized Makefile tailored for the BOARD=FTHR configuration, successfully bypassing the default TFT display requirements to keep the compiled code lean and highly specialized.
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SPI Configuration: Standard single-width SPI clocked at 1 MHz.
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Sensor Interfacing: Precise bit-banging algorithm implementing host-start signals (18ms low pulse) followed by sensor response polling.
Future Scope
I plan to utilize the deep sleep modes of the MAX32672 to minimize the duty-cycle power consumption down to microamps, alongside designing a custom PCB shield to natively plug the SX1278 directly into the Feather form factor.
Special thanks again to DigiKey and Circuit Digest for providing the hardware that made this development possible! Feel free to ask any questions about the software timing or the SPI architecture in the comments below!