A programmable HD-OBD telematics platform for passenger cars, trucks, buses, and heavy-duty vehicles.

Freematics ONE+ Model H is a compact, all-in-one vehicle telematics device with an OBD-II Type B, also known as HD-OBD, connector. It supports both standard passenger vehicles with 12V systems and heavy-duty vehicles with 24V systems, making it suitable for fleet tracking, vehicle diagnostics, CAN bus monitoring, SAE J1939 applictions, and connected automotive development.

Built around the ESP32, Model H integrates 4G LTE cellular connectivity, GNSS positioning, motion sensing, microSD storage, Wi-Fi, Bluetooth, and external I/O in a single ready-to-program device. It is designed for developers, integrators, and fleet solution builders who need reliable vehicle data acquisition and real-time connectivity without building custom hardware from scratch.

Key Features

• HD-OBD connector for heavy-duty vehicle applications
• 12V and 24V vehicle support for passenger cars and heavy-duty vehicles
• Standard OBD-II access for PIDs, DTCs, VIN, and ECU data
• CAN bus sniffing for advanced vehicle network monitoring
• SAE J1939 access for broadcasted PGN and SPN data from compatible heavy vehicles
• Arduino-programmable ESP32 platform with built-in Wi-Fi and Bluetooth
• Integrated 4G LTE CAT4 cellular module for high-speed data transmission
• Integrated GNSS positioning with onboard antenna
• Motion sensing for G-force measurement, movement detection, and low-power monitoring
• microSD storage support for onboard data logging
• BLE app connectivity for configuration and monitoring from a mobile device
• External I/O socket for sensors, controllers, and custom peripherals

Hardware Overview

Freematics ONE+ Model H combines vehicle interface, positioning, cellular connectivity, storage, and application processing in one compact OBD device.

Specifications

• Espressif ESP32 with 16MB Flash, 8MB PSRAM, 32K RTC
• Built-in 802.11 b/g/n HT40 Wi-Fi
• Dual-mode Bluetooth, including Classic Bluetooth and BLE
• Integrated ICM-42627 motion sensor
• Integrated u-blox M10 GNSS module and antenna
• Integrated 4G LTE CAT-1 or CAT-4 cellular module
• Built-in buzzer
• Enclosure dimensions: 60x48x20mm

Physical Interfaces

• OBD-II Type B (HD-OBD), male connector
• microUSB port
• microSD card slot
• SIM card slot
• GPIO socket (Molex)

Vehicle Compatibility

Freematics ONE+ Model H plugs into an OBD or HD-OBD port and supports both standard OBD-II vehicles and heavy-duty vehicles using SAE J1939.

For passenger vehicles, the OBD port is usually located under the steering column. To confirm OBD-II support, check the emissions or compliance sticker under the hood.

Supported protocols include:

• SAE J1939
• CAN 500Kbps / 29-bit
• CAN 250Kbps / 29-bit
• CAN 500Kbps / 11-bit
• CAN 250Kbps / 11-bit
• KWP2000 Fast
• KWP2000 5Kbps

Heavy-Duty Vehicle Support

Model H is designed for applications that require data access from commercial and heavy-duty vehicles. Through SAE J1939 support, it can access broadcasted PGN and SPN data from compatible ECUs, making it suitable for trucks, buses, machinery, fleet vehicles, and other 24V vehicle platforms.

External I/O

Freematics ONE+ Model H includes a 4-pin external I/O socket for connecting additional sensors, controllers, or custom hardware. The socket provides two ESP32 GPIO pins, controllable VCC, and GND.

With a Molex-to-2.54mm Dupont conversion cable, external components can be connected easily during prototyping or integration.

Dupont connector wiring:

• Black: GND
• Red: VCC
• White: GPIO34
• Green: GPIO26

GNSS Positioning

Freematics ONE+ Model H integrates u-blox M9 GNSS module and active ceramic antenna for vehicle positioning. The module can be configured programmatically, while the NMEA data stream is decoded in real time by the co-processor and made available to the ESP32 for logging, processing, or transmission.

This allows applications to combine location, speed, movement, and vehicle ECU data in a single data stream.

Bluetooth and Mobile App Support

Freematics ONE+ Model H includes dual-mode Bluetooth and can connect to the Freematics Controller App over BLE when using datalogger sketch or telelogger sketch.

This allows the device to be configured and monitored from a mobile device without requiring a wired connection.

Cellular Module

Freematics ONE+ Model H includes an integrated SIM7670 LTE Cat 1 module, or SIM7600A-H/SIM7600E-H LTE module for high-speed cellular connectivity.

SIM Card

A microSIM card is required for cellular network connectivity. Insert the SIM card into the slot as shown below.

Global SIM cards like Hologram IoT SIM card are supported.

microSD Storage

The built-in microSD slot is located under the side cover and is connected to the ESP32 via SPI. It can be accessed using the standard Arduino SD library.

This makes it easy to log OBD-II data, SAE J1939 data, GNSS coordinates, motion data, diagnostic information, and custom sensor readings locally.

Buzzer

The internal buzzer is connected to ESP32 GPIO25 and can be driven using PWM or DAC output.

It can be used for alerts, status indicators, driver feedback, or application-specific notifications.

Low-Power Mode

Freematics ONE+ Model H can enter and exit low-power mode programmatically. When GNSS, cellular, and Wi-Fi peripherals are powered off, power consumption is around 10mA.

This helps reduce vehicle battery drain while still allowing the main controller to run lightweight tasks such as motion detection through the onboard MEMS sensor.

Model Comparison

Development

Freematics ONE+ Model B is designed for developers who want to build custom vehicle-connected products without starting from bare hardware.

Freematics provides a dedicated Arduino library for accessing the device’s hardware resources, along with functional reference Arduino sketches for common use cases. With basic Arduino knowledge, you can begin collecting vehicle data, logging it to microSD, reading GNSS coordinates, transmitting data over cellular or Wi-Fi, and building your own automotive applications.

For a simpler development workflow, Freematics Builder provides a graphical interface for configuring, compiling, and uploading Arduino sketches. Advanced users can also develop with PlatformIO, Arduino IDE, Arduino makefile, or ESP-IDF-based workflows.

For setup instructions and development details, refer to the Developers Guide.

Links

• Arduino Library
• Sample Arduino Sketches
• Developers Guide
• Schematics
• Telelogger with ESP-IDF