F16: OBD2 Reader
Contents
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OBD2 Reader
Abstract
OBD2
The OBD2 reader is an on board diagnostic device that will translate the diagnostic code from the vehicle's ecu to an understandable and readable data for the user. This device will use several protocols learned in 146 lab as well as other techniques featured in the Socialledge Wiki in order to implement the design. The cars onboard ECU takes all the sensory data from several sensors and units and translates this into hexadecimal number and outputs it through its OBD2 port. Our OBD2 ready device will link with the car’s ECU and takes this information and compares it to the database codes that will indicate the problem with the vehicle. Once the codes from the ECU to our board match they will display the result on the additional LCD device. The LCD device will be implemented on top of our board using the I2C protocol. This device will display the error with the vehicle with diagnostic suggestions and methods of approach.
CAN Bus
CAN(Controlled Area Network) Bus is the bus standard for all vehicles. CAN Bus allows multiple control units and devices to communicate with one another and no host computer is needed. Some devices that can be found connected to the CAN Bus are the control unit for the airbags, the anti-lock braking system, the power steering system,the sensor that detects when an object is too close to your car and the OBD connector.
The CAN Bus is made up of two wires: CAN-H (CAN High) and CAN-L (CAN Low). Both wires connect to all devices on the bus. When the CAN-H receives a signal, the CAN-L also receives the same signal but with an opposite amplitude. The reason for this is to reduce the chance of the data being corrupted because it is less vulnerable to noise. The CAN-H wire can go from 2.5V to 3.75V and the CAN-L wire respectively can go from 2.5V down to 1.25V.
When the CAN Bus is implemented on a vehicle, both CAN-H and CAN-L wires must be twisted together with two 120 Ohm terminating resistors. By having the wires twisted together, they are able to eliminate any noise. The two terminating resistors are connected to both ends of the bus to eliminate any signals from reflecting.
The CAN bus system has two different formats for the message frame, 2.0A and 2.0B. The difference is that 2.0A is the standard and uses 11 bits in the arbitration field, and 2.0B is the extended and uses 29 bits in the arbitration field.
The CAN Bus data message frame is composed of a Starting Frame, an Arbitration Field, a Control Field, Data Field, Cyclic Redundancy Check, Acknowledge Field, and End of Frame. The Starting Frame is used to indicate the start of a message when it is zero. The Arbitration Field is used to define the message priority. The Control Field is used to describe the length of the data being sent. The Data Field is used to send the actual data to the other CAN nodes. The Cyclic Redundancy Check is used to detect any errors in the data. The Acknowledge Field is used to let the transmitter know that they successfully received the data. The End of Frame is used to indicated the end of the data.
In the CAN system, there is no control host. When a CAN node is about to send data into the bus it first checks to see if the bus is is busy. If the bus is not busy, the CAN node will send a message frame to the bus. The message frame does not contain a destination address so the message frame will be received by all nodes on the bus. Depending on the Arbitration Field, each CAN node will decide if they should ignore or accept the frame. When more then one CAN node try to send a frame in to the BUS at the same time, the node with the lower Arbitration ID will have the higher priority to the bus. The lower priority will have to wait until the higher priority is done.
Objectives & Introduction
This project aims to design an OBD2 reader using the SJOne LPC 1758 board. The reader will display a vehicle's Engine Control Unit (ECU) information via an LCD screen.
Objectives:
- Interface the SJOne board with the OBD2 reader
- Store and read external memory module through SJOne board
- Interfacing SJOne to external LCD or OLED display
Sensors and Peripherals Used:
- ECU (information source device)
- SJOne (for processing information)
- External Memory and Memory Interface
- LCD or OLED (display vehicle diagnostics)
Team Members & Responsibilities
- R Nikfar
- Electrical Engineering Advising, Can Bus protocol Design, Eagle PCB design, Electrical Components, Firmware Coding, and Mechanical Engineering sensor and Component Debugging.
- Samira Oliva
- Samuel Palomino
- Erik Sanchez
- Setting up the memory unit.
Schedule
| Week # | Start Date | End Date | Planned Tasks | Status | Actual Outcome |
|---|---|---|---|---|---|
| 1 | 10/30/16 | 11/05/16 |
|
Completed |
|
| 2 | 11/06/16 | 11/12/16 |
|
In Progress | TBA |
| 3 | 11/13/16 | 11/19/16 |
|
Incomplete | TBA |
| 4 | 11/20/16 | 11/26/16 |
|
Incomplete | TBA |
| 5 | 11/27/16 | 12/03/16 |
|
Incomplete | TBA |
| 6 | 12/04/16 | 12/10/16 |
|
Incomplete | TBA |
| 7 | 12/11/16 | 12/17/16 |
|
Incomplete | TBA |
| 8 | 12/18/16 | 12/20/16 |
|
Incomplete | TBA |
Parts List & Cost
Give a simple list of the cost of your project broken down by components. Do not write long stories here.
| Item | Qty. | Price (Total) | Description |
|---|---|---|---|
| SJOne Board | 1 | $80.00 | SJOne board |
| OBD2 to DB9 Adapter | 1 | $6.99 | Connects the vehicle's ECU to SJOne board |
| OLED Display | 1 | $9.99 | I2C 128x64 Display Module |
| TBA | X | $X | TBA |
Design & Implementation
The design section can go over your hardware and software design. Organize this section using sub-sections that go over your design and implementation.
Hardware Design
Discuss your hardware design here. Show detailed schematics, and the interface here.
Hardware Interface
In this section, you can describe how your hardware communicates, such as which BUSes used. You can discuss your driver implementation here, such that the Software Design section is isolated to talk about high level workings rather than inner working of your project.
Software Design
Show your software design. For example, if you are designing an MP3 Player, show the tasks that you are using, and what they are doing at a high level. Do not show the details of the code. For example, do not show exact code, but you may show psuedocode and fragments of code. Keep in mind that you are showing DESIGN of your software, not the inner workings of it.
- communication Protcols
Implementation
This section includes implementation, but again, not the details, just the high level. For example, you can list the steps it takes to communicate over a sensor, or the steps needed to write a page of memory onto SPI Flash. You can include sub-sections for each of your component implementation.
Testing & Technical Challenges
Describe the challenges of your project. What advise would you give yourself or someone else if your project can be started from scratch again? Make a smooth transition to testing section and described what it took to test your project.
Include sub-sections that list out a problem and solution, such as:
My Issue #1
Discuss the issue and resolution.
Conclusion
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Project Video
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Project Source Code
References
Acknowledgement
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References Used
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Appendix
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