The Obd2 Click represents a significant leap forward for anyone seeking to understand and interact with their vehicle’s intricate systems. This innovative click board, powered by the sophisticated STN1110 Multiprotocol OBD to UART Interface from ScanTool Technologies, opens up the world of on-board diagnostics (OBD) to developers, car enthusiasts, and professional mechanics alike. It facilitates seamless communication with your car’s Electronic Control Unit (ECU) through a variety of OBD II diagnostic protocols, including CAN, K LINE, L LINE, and J1850. The intelligent STN1110 IC acts as a translator, processing requests sent from a microcontroller (MCU) via UART and relaying meaningful responses back from the vehicle’s network.
The power of the OBD2 click lies in its core component, the STN1110 Multiprotocol OBD to UART IC. Built around a robust 16-bit processor and featuring a substantial memory buffer, this IC excels in automatic protocol detection. Crucially, it boasts full compatibility with the popular ELM327 and ELM327 Extended AT command sets, ensuring broad software support and ease of use. Furthermore, it supports UART speeds up to an impressive 10 Mbps, enabling rapid data transfer. These features combine to make the OBD2 click an ideal solution for a wide spectrum of applications, from creating bespoke car dashboards and precise OBD data loggers to developing advanced automotive diagnostic scan tools.
Diving Deeper: How OBD2 Click Functions
OBD, or On-Board Diagnostics, is a standardized system that revolutionized vehicle maintenance and analysis. It provides a computer-based framework for monitoring and diagnosing vehicle performance. OBD II, the second generation of this standard introduced in the 1980s, has evolved significantly. Starting from simple warning lights, OBD has matured into a comprehensive digital diagnostic standard, characterized by clearly defined communication protocols and standardized connector types.
OBD2 Click Board: A close-up view of the interface for vehicle diagnostic systems, highlighting the compact design and components.
The OBD II standard defines a set of PIDs, or Parameter IDs, which serve as standardized requests to access data from the vehicle’s ECU. These PIDs allow users to query specific parameters within the vehicle’s control network. The latest OBD II standard outlines 10 modes of operation, though manufacturers can choose to implement a subset or add proprietary modes. Each PID has a strictly defined response format, along with instructions on how to decode the raw data into understandable information.
The STN1110 chip at the heart of the OBD2 click acts as an OBD-to-UART interpreter. It skillfully translates communication between the various OBD-II protocols and the simpler UART interface. Its ELM327 command set compatibility is a major advantage, ensuring compatibility with a vast ecosystem of existing OBD-II software and tools. The OBD II standard also mandates the inclusion of a standardized Diagnostic Link Connector (DLC) in all compliant vehicles. This universal connector enables tools like the OBD2 click to interface with a wide range of vehicles using a single physical connection.
To ensure reliable communication across the diverse physical layers of in-vehicle networks, the OBD2 click integrates additional components. It incorporates the MCP2561, a CAN transceiver compliant with the ISO-11898 standard, for robust CAN signal transmission. The LM339 quad differential comparator IC handles signal conversion for K Line, L Line, and J1850 protocols, transforming them into a compatible digital format for the STN1110. An analog pin on the STN1110 provides direct car battery voltage measurement. This feature proves invaluable for verifying UART communication and offers a quick voltage check via a voltage divider, bypassing the need for complex communication protocols.
For user feedback and monitoring, the OBD2 click is equipped with four LEDs. These LEDs visually indicate data activity on both the OBD (OBD RX/TX) and UART (UART RX/TX) sides of the click board. In addition to the standard Power LED (PWR), a dedicated BAT LED signals the presence of battery voltage at the OBD connector, offering a quick visual confirmation of power. The OBD2 click utilizes a standard D-Sub 9 connector (DB9), allowing for easy connection using readily available OBDII cables.
Important Note: The OBDII cable is not included with the OBD2 click package and must be purchased separately.
Once the initial protocol auto-detection is complete (which may necessitate turning on the vehicle’s ignition and sending an initialization AT command), the STN1110 manages all communication between the vehicle’s ECU and itself. This automation allows users to effortlessly retrieve vehicle system status by sending simple AT commands via the UART pins of the OBD2 click. MikroElektronika provides user-friendly libraries that simplify the communication process between the click board and the MCU via UART. Comprehensive documentation detailing the full range of available AT commands is readily accessible in the product resources.
Technical Specifications
| Feature | Specification |
|---|---|
| Type | CAN, OBD |
| Applications | Vehicle diagnostics, custom car dashboards, OBD data logging, automotive scan tools. |
| On-board Modules | STN1110 (ScanTool), MCP2561 (CAN Transceiver), LM339 (Quad Differential Comparator) |
| Key Features | Full OBD-II protocol support, ELM327 AT command set compatibility, high-speed communication, automatic protocol detection, large memory buffer, direct battery voltage monitoring. |
| Interface | UART |
| ClickID | No ClickID |
| Compatibility | mikroBUS™ |
| Click board size | L (57.15 x 25.4 mm) |
| Input Voltage | 3.3V |
| Category | Click Boards |
Pinout Configuration
The table below details the pin mapping between the OBD2 click and the mikroBUS socket.
| Notes | Pin | mikroBUS Pin | Pin | mikroBUS Pin | Notes |
|---|---|---|---|---|---|
| NC | 1 | AN | 16 | PWM | |
| Reset | RST | 2 | RST | 15 | INT |
| NC | 3 | CS | 14 | RX | |
| NC | 4 | SCK | 13 | TX | |
| NC | 5 | MISO | 12 | SCL | |
| NC | 6 | MOSI | 11 | SDA | |
| Power | 3V3 | 7 | 3.3V | 10 | 5V |
| Ground | GND | 8 | GND | 9 | GND |
Onboard Indicators and Settings
| Label | Name | Default | Description |
|---|---|---|---|
| PWR | Power LED | – | Power indication LED |
| BTR | Battery OK | – | OBD battery voltage indicator LED |
| RX OBD | RX OBD LED | – | Indicates data reception on the OBD interface |
| TX OBD | TX OBD LED | – | Indicates data transmission on the OBD interface |
| RX UART | RX UART LED | – | Indicates data reception on the UART interface |
| TX UART | TX UART LED | – | Indicates data transmission on the UART interface |
Software Ecosystem
Robust software support is available for the OBD2 click through MikroElektronika’s LibStock platform. This includes a comprehensive library and a demo application, both designed using MikroElektronika compilers and mikroSDK. The demo application is compatible across MikroElektronika’s extensive range of development boards.
Library Overview
The provided library contains a set of generic functions crucial for interacting with the OBD2 click module.
Key Functions:
obdII_sendCommand: Transmits a user-defined command to the module.obdII_readResponse: Reads the module’s response currently stored in the buffer.obdII_process: Implements a state machine for managing communication flow (must be called periodically).
Example Application
The demo application showcases how to retrieve RPM (revolutions per minute) data from a vehicle’s ECU.
- System Initialization: Sets up the UART module and configures necessary GPIO pins.
- Application Initialization: Powers on the OBD2 click module and configures it for automatic protocol detection using the “ATSP0” command.
- Application Task (Code Snippet): Sequentially sends the RPM command and processes the response to extract the RPM value.
void applicationTask() {
uint8_t tmp[ 25 ];
obdII_sendCommand( &RPM_CMD[0] );
while( !obdII_responseReady() ) ;
obdII_readResponse( &rsp[0] );
memcpy( &tmp[0], &rsp[11], 4 );
tmp[5] = 0;
rpm = xtoi( &tmp[0] );
rpm = rpm / 4;
WordToStr(rpm, &tmp[0]);
mikrobus_logWrite( "Current RPM : ", _LOG_TEXT );
mikrobus_logWrite( tmp, _LOG_LINE );
}Important Note: Vehicle-specific command sets may vary. The RPM reading routine provided in the example may not be universally applicable to all vehicles.
The complete application code and ready-to-use project files are available on LibStock.
Supporting MikroElektronika Libraries Used in the Example:
- Conversions
- String
- Stdlib
Additional Information
Depending on your chosen development board, you might require a USB UART click, USB UART 2 click, or RS232 click to establish a connection to your PC for development, particularly if your board lacks a built-in UART-to-USB interface. The terminal utility integrated within all MikroElektronika compilers, or any compatible terminal application, can be used to monitor and interpret the data transmitted by the OBD2 click.
mikroSDK Integration
This Click board™ benefits from full mikroSDK (MikroElektronika Software Development Kit) support. To ensure seamless operation of mikroSDK-compatible Click board™ demo applications, mikroSDK should be downloaded from LibStock and installed for your specific compiler.
For in-depth information regarding mikroSDK, please consult the official mikroSDK page.
