Smart IoT-Based Thermal Monitoring System Development Using Renesas RA6M4 MCU

In cold chain logistics, there are extreme risks associated with temperature excursions. When there is a temperature excursion, the loss can be catastrophic: loss of vaccines, food safety, regulatory non-compliance among others.

To solve this problem, we have developed "ThermoGrid", a thermal monitoring device with real-time visibility, predictive alerts, and seamless integration into your workflow that incorporates Renesas' RA6M4 MCU.

"ThermoGrid" is a total end-to-end solution where we developed the entire integrated solution from PCB design through cloud infrastructure for scalability by integrating hardware, firmware, software and enterprise systems.

The cold chain logistics industry needs accurate temperature control throughout its transportation and storage processes. Products like biologics, dairy, and seafood can become unusable with just a small amount of temperature deviation.

Many traditional data loggers are passive devices that rely on manual data retrieval and analysis after an event. With ThermoGrid's active monitoring and real-time alerts, users can take proactive actions to ensure regulatory compliance while utilizing cloud-based analytics.

Selecting the Controller

We selected the Renesas RA6M4 Microcontroller (MCU) for its overall good balance of performance and low power use, along with its ability to provide security:

• ARM Cortex-M33 Core 200 MHz
• TrustZone® and Secure Crypto Engine for Secure Boot and Over-the-Air (OTA) Updates.
• Flexibility of Connectivity: USB, CAN, UART, SPI, I2C

PCB Design

• Multi-layer PCB with the ability to isolate the Analog & Digital (isolation between analog and digital) domains of the board.
• Consistent accuracy within +/- 0.1 degree Celsius temperature (includes both digital & analog sensors)
• Includes Battery Management Circuit for Rechargeable Lithium Ion batteries
• Option to include GPS Module for Location-based Logging of Temperatures
• Supports BLE + LTE-M through the use of a hybrid connectivity Radio Frequency (RF) module.

Controller Selection

We chose the Renesas RA6M4 MCU for its balance of performance, low power, and security:

• ARM Cortex-M33 core @ 200 MHz
• TrustZone® and Secure Crypto Engine for secure boot and OTA updates
• Flexible connectivity: USB, CAN, UART, SPI, I2C

PCB Design

• Multi-layer PCB with isolated analog and digital domains
• Precision temperature sensors (digital and analog) with ±0.1°C accuracy
• Battery management circuit for rechargeable Li-ion cells
• Optional GPS module for location-tagged temperature logs
• RF module: BLE + LTE-M for hybrid connectivity

Firmware Software

• RTOS – ThreadX for predicted orderly sequencing
• Sensor drivers – Developed in-house with calib. capabilities
• Data repository – Circular buffer w/ DMA to log data
• Security (n) – AES-256 Encryption, secure bootloader and firmware signing.
• Power management – Sleep mode w/ wake-on-threshold logic.

Mechanical Design & Manufacturing

• Enclosure: Polycarbonate housing that is rated as IP67 and has insulation to provide thermal protection.
• Mounting: Combination of magnetically attached base and strap slots allow for flexible mounting options.
• Display: Screen made of low-power e-ink is used to display a local status of the device.
• Manufacturing: We managed the tooling for the injection molded parts, surface mount technology assembly and final quality assurance.
• Testing: Performance was tested using an environmental chamber, drop tests and RF certification.

Infrastructure Overview:

• The Ingestion layer consists of an MQTT broker that accepts telemetry messages and a RESTful API to support batch uploads of data.
• The Processing layer contains both a real-time rule engine and enabled with anomaly detection capabilities.
• The Storage layer contains a Time-Series Database (InfluxDB) and a Relational Database (PostgreSQL).
• The Security Layer includes support for OAuth2, TLS 1.3, and audit logging.
• Scalability will be achieved through containerized microservices using Kubernetes for orchestration.

Feature Set:

• Device provisioned via QR code or NFC.
• Geo-fencing alerting provided when routes deviate from expected paths.
• Compliance reporting aligned with FDA and WHO standards.
• Multi-tenant support provided to logistics service providers and their client base.

Desktop Application

• Built with .NET MAUI for cross-platform deployment
• Features: Device configuration, historical data visualization, export tools

Web Portal

• Developed using Angular + NestJS
• Role-based dashboards for fleet managers, QA teams, and compliance officers
• Custom report builder with drag-and-drop analytics

Mobile App

• Native apps for Android and iOS
• Push notifications for threshold breaches
• Offline sync for field operatives in low-connectivity zones

SDK/API Usage

• RESTful APIs integrate with ERP/WMS/TMS systems through web interfaces.
• SDKs available in Python, Javascript, C#. Use for custom workflows and access other functions.
• Webhooks enable event triggering without polling the API.

Predictive Analytics

• ML models trained on historical temperature profiles
• Forecasting potential excursions based on route, weather, and container type

OTA Updates

• Secure firmware updates via cloud
• Configurable update windows to avoid disruption

Diagnostics & Logging

• Structured logs in JSON format
• Remote diagnostics via cloud console
• Device health scoring based on uptime, battery, and signal metrics

Internationalization

• Multi-language support across apps and dashboards
• Timezone-aware reporting for global operations

Regulatory Confidence:

80% reduction in time spent preparing for audits because of automated compliance reporting.

Customer Trust:

Improvements in real time visibility resulted in increased SLA adherence and improved customer satisfaction.

Operational Efficiency:

Reduced manual interventions and increased the efficiency of route planning using system-generated routing data.

Scalability:

Modular design enables customers to deploy across 300+ vehicles within six months after purchase.

Cost Optimization:

Iterative refinements to both PCB and enclosure designs decreased BOM cost by 18%.

• Factory calibration of sensors is important for achieving consistent accuracy across batches of sensors.
• LTE-M provided a higher coverage area than NB-IoT in rural areas.
• TrustZone and secure boot were crucial elements for enterprise to adopt the product.
• QR-based provisioning and mobile alerts to simplify field deployment were extremely helpful.
• Kubernetes auto-scaling enabled scalability in handling peak ingestion as fleet rollouts occurred.

Renesas microcontrollers allow for the creation of strong, secure and scalable solutions for industry. The ThermoGrid product has been developed from the ground up, including from circuit board to cloud, resulting in a product that is both technically viable and transformational to operations.

With our end-to-end approach we were able to meet many of the more demanding requirements within industry while at the same time giving logistics firms the ability to gain real-time actions, gain insight into operational attributes, control order flows as they happen, and seamlessly integrate with all other supply chain components of the future.