Designing a Fast & Secure

OBD Scan System using Mistral i.MX6 Nano SOM

Application Note

Overview

On-Board Diagnostic systems were introduced by

Automotive OEMS in late '70s & early 1980's enabling

electronic means to control engine functions and

diagnose engine problems. Though OBD systems are

primarily intended to meet EPA emission standards,

with the introduction of OBD-II, on-board diagnostic

systems have become more sophisticated, providing

almost complete engine control & monitoring for parts

of the chassis, body and accessory devices, as well as

the control network of the car. OBD-II became a

universal inspection and diagnosis method for vehicle

diagnostics and most recent automobiles are OBD-II

compliant providing a standard interface to collect data

from engine sensors, using a Scantool. Fast & secure

boot-up, small form-factor and quick processing and

dissemination of data are few crucial parameters

expected from an OBD Scantool.

This application note gives a technical perspective on

how Mistral i.MX6 Nano SOM can be adapted to meet

the technical and functional requirements, along with

an OBD-to-RS232 Interpreter [ELM327] for designing

the core architecture of an OBD Scantool.

i.MX6 Nano SOM -

The Nano SOM from Mistral is a small form factor, high

performance, low cost, ready-to-use System on Module

(SOM) built around the powerful 800MHz Quad/Dual

Core i.MX6 SoC from NXP. The i.MX6 offers extensive

integration capability such as dual camera, LCD, PCIe,

HDMI output, NOR flash, Ethernet, Audio and an easily

deployable architecture that favours fast time-to-market.

Features

Hardware

! i.MX6D/Q800MHz ARM Cortex- A9 processor

! 1GB LPDDR2 PoP memory

! Wi-Fi + BT 4.0 Module

! 8GB eMMC

! Can be operated by powering up from a battery

! Weighs 8 Grams

Software

! Linux Kernel 4.1

! Android

! Yocto BSP

! u-Boot 2015.04

Basic Configuration

Design Considerations

Let's now look at the elements that need attention while

designing the electronics sub-system for an OBD-II

Scantool. The latest trend being miniaturisation and giving

maximum power to handheld scan devices, the electronic

sub-system of a Scantool needs to be very compact in

size, light-weight, battery operated while having high

processing capability. The i.MX6 Nano SOM is a high-

performance unit which meets the above mentioned

essential parameters. The recommended OBD-to-RS-

232 interpreter ELM327 is designed to act as a bridge

between the On-Board Diagnostics (OBD) ports of the

vehicle and the standard serial interface of the Scantool.

Additionally, in order to automatically detect and interpret

nine OBD protocols, the ELM327 also provides support

for high-speed communication, a low power sleep mode,

and the J1939 truck and bus standard. ELM327

communicates with the Nano SOM over RS232 serial

connection. Using terminal programs you can

send/receive data from the interpreter.

The Nano SOM has i.MX6D/Q core processor, which

provides high processing power and Wi-Fi/BT module

through which the interpreted data can be streamed.

ELM327 detects and captures data from the automobile

unit, which is interpreted, processed and converted into

packet data and transferred to i.MX6 Nano SOM. Data

received from ELM327 is fine-processed and send to a

LCD display powered by the Nano SOM or streamed over

WiFi/BT to suit the client application.

Software Design & Integration

The Linux based Yocto Jethro runs on the i.MX6 Nano

SOM, evokes a multithreaded environment to speed the

task execution. Yocto Jethro with its low latency and high

accuracy supports near real-time access to rapidly

changing data. Yocto Jethro can be customized according

to the Scantool requirements in order to improve the

overall throughput of the device.

The information gathered is analysed and displayed in the

LCD display mounted on the device. The low level system

software read the data from vehicle through OBD

connector using OBD-II PIDs, decodes the data as per the

OBD-II standards. Once the PID is entered, the scan tool

sends it to the vehicle's controller–area network (CAN)-

bus. A device on the bus recognizes the PID and reports

the value for that PID to the bus. The scan tool reads the

response, and displays it over the LCD or streams the

data to Mobile Application over Wi-Fi or Bluetooth to the

technician or car owner. The results can also be viewed on

custom application running on PC's and Mobiles.

A user-friendly GUI is key to the commercial success of

the Scantool. The developer can design intuitive Qt based

application that provides a user friendly interface for

Scantool. Qt provides the flexibility to develop integrated

applications for embedded, mobile, desktop and

touchscreen devices.

Product Implementation Approach

The diagram below showcases the fundamental

architecture of the Scantool using Nano SOM. The Nano

SOM by default has all the key functional components

required for the faster dissemination of data to client in its

original design. This is a huge advantage for the

developer, save time and cost as no customisation is

warranted on the Nano SOM to meet the system

requirement.

i.MX6D/Q

LPDDR2

(PoP)

Wireless module

Wi-Fi/BT

Storage-

eMMC

PMIC

Expansion Connectors

Nano SOM Architecture

The carrier board that carries the core architecture of the

Scantool needs to be custom designed. The carrier

module should comprise Display, Audio and Video,

Ethernet, Wireless and other interfaces as required.

Preferred interfaces on the carrier module:

! Display interfaces such as LVDS and touch interface,

MIPI DSI display with Touch control

! Audio interfaces for Voice Alerts

! MicroSD connector for expandable memory

! USB2.0 Host

! Ethernet & Wireless

! Debug Support

The i.MX6 Nano SOM comes with the following

software functionalities

! Linux Kernel with support for various interfaces like

I2C, MIPI, CSI, GPIO, SPI, UART, SD/MMC, Ethernet,

Display Sub-system, USB Host and USB OTG

! Support for WLAN and Bluetooth Stack

! Support for 9-axis sensor

! Support for SD and eMMC boot

! QT support for application development

! Security features which can be enabled to

protect data.

Transfer of Car Engine Data to i.MX6 Nano SOM thru ELM 327

Benefits to the customer by using

Nano SOM

! Powerful Quad/Dual Core ARM Cortex-A9 Processor

ensures fast & secure boot up

! Comes with sufficient memory and power required

for getting the OS and peripheral functionalities

mapped

! Wi-Fi IEEE802.11 a/b/g/n paves way for video

streaming

! BT4.0 for short range communications

! Small form factor (44mm x 26mm) & Light-weight

module weighing just 7.0 grams enables the

customer design relatively small & user-friendly

devices

Quick to Market - Leverage over Mistral

VISE Board

Mistral VISE board is a powerful i.MX6 development platform

built around the i.MX6 Nano SOM. Product developers can

accelerate their OBD Scantool development by developing the

custom software and applications on the VISE Board while the

custom carrier board is getting built. This will help complete the

product development and testing faster, saving cost and time.

About Mistral

Mistral is a technology design and systems engineering company providing end-to-end solutions for product

design and application deployment. Mistral is focused in three business domains: Product Engineering

Services, Aerospace & Defense and Homeland Security. Mistral provides total solutions for a given

requirement, which may include hardware design, embedded software development, systems integration and

customized turnkey solutions. Mistral's strategic partnerships with leading technology companies help provide

customers with a comprehensive package of end-to-end solutions.

Mistral's Product Engineering Services are delivered through a proven development process, designed for

embedded product development. Mistral's hardware and software team works together in a seamless manner

providing expert product designs covering board and FPGA Designs, BSP & Firmware developments,

Embedded Application developments, integration of 3rd party solutions, Verification/Validation, Product

prototyping, Production coordination and Product Sustenance services.w

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Mistral's Expertise

Mistral can provide development services to the clients to build a custom carrier board around Nano SOM

and assimilate ELM327. Board can be designed to suit the end product basis the clients need. Mistral offers

System software and application development services considering the various applications of the device.

Mistral's expert team of engineers have helped several customers realize their Product designs with the

development of smart, compact and power efficient electronics systems and the related software for the

same (BSP and Apps). Mistral's expertise in Product Development includes embedded applications,

software design and development, multi-sensor integration, wireless connectivity, power and battery

management, design of hardware for small form factor and multi-board designs, cloud/web application

development services and FCC, CE, UL Certification.