Difference between revisions of "S15: Real Time Brake Assist (RTBA)"

Revision as of 06:40, 20 May 2015

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Real Time Brake Assist (RTBA)

Abstract

Real time brake assist is an automotive application that helps the user in calculating a safe braking distance with respect to the car in the front. The system makes use of a LiDAR sensor for judging the car’s proximity to the car ahead of it and uses the diagnostic port (OBDII) to pull up the car’s current speed from the ECU. Based on the collected data, it will calculate the safe braking distance and will provide visual indicators for the same.

Objectives & Introduction

What we would like to accomplish is the following:

Provide a user friendly solution to brake assistance by analyzing car's data through OBD-II.
- Lidar to detect distance.
- OBD-II interface with SJSU One Board.
- Special I2C circuitry for wiring the lidar from the front of the car to inside of the car.
Provide a simple mobile application which reads the OBD-II data through bluetooth as additional feature to the braking solution. It would provide the following indicators:
- Car Speed(mph)
- Braking Distance(ft)
- Proximity(ft)
- Safety Warning
Additional Features:
- TBD

Team Members & Responsibilities

Sahil Kataria
- Architecture Design, Hardware & Software Development, Integration
Julio Fuentes
- I2C Communication, Hardware Development
Shaw Ken Chang
- Android App/Bluetooth bridge, System Integration, brake algorithm, new features.
Naghma Anwar
- CAN Communication, Software Development

Schedule

Show a simple table or figures that show your scheduled as planned before you started working on the project. Then in another table column, write down the actual schedule so that readers can see the planned vs. actual goals. The point of the schedule is for readers to assess how to pace themselves if they are doing a similar project.

Week #	Start Date	End Date	Task	Status	Result
1	03/10/15	03/16/15	Get the parts: Order LIDAR-Lite module from sparkfun Order CAN transceiver chip Acquire OBD2 extender cables	Completed	As of 03/16/15 All parts arrived on time
2	03/17/15	03/23/15	Have a group meeting: Work on architecture design Assign tasks to each group member	Completed	As of 03/23/15 Project design finalized Members were assigned their tasks
3	03/24/15	03/30/15	Design a small DB9 to CAN transceiver connector board Get all the parts that is required to be soldered on the connector board Finish hardware soldering	Completed	As of 03/30/15 Connector board ready for testing
4	03/31/15	04/06/15	Do some research on OBD-II Find out what PID commands are needed to fetch vehicle speed from car's ECU Write code to send proper command to OBD-II port using CAN communication	Completed	As of 04/06/15 Code written Ready for testing
5	04/07/15	04/13/15	Work on I2C communication between LIDAR-lite module and SJOne board Start developing android app to display speed, distance, proximity and safety alert information Set up a repository on GitLab and start collaborating.	Completed	As of 04/13/15 GitLab collaboration started Bluetooth android bridge: function check was done and basic software was written but at the moment throwing some error
6	04/14/15	04/20/15	Do some research on differential driver for the I2C to make sure that the signals reach reliably to the front of the car Start testing for CAN communication between OBD2 port and SJOne board Start testing for I2C communication between LiDAR-lite and SJOne board	Ongoing	As of 4/21/2015 Bluetooth android bridge: rewrite the android UI and android bluetooth read function for more stable communication. I2C communication successfully established between LiDAR and SJOne board CAN communication throwing error
7	04/21/15	04/27/15	Design an algorithm to calculate the safe braking distance Display this information on android app to notify the user Assign different colors to each state: Yellow (safe distance), Orange (safe but not too safe), Red (danger zone, car should stop immediately)	Completed	As of 5/11/2015 Algorithm developed. Took longer than expected because of stuck CAN communication
8	04/28/15	05/04/15	Start calibrating the safe braking distance Fine tune the distance and speed Make android app more informative and user friendly by adding sound alerts	Ongoing	As of 5/4/2015
9	05/05/15	05/11/15	Final Testing	Ongoing
10	05/12/15	05/25/15	Project Demo	Scheduled

Parts List & Cost

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Item#	Part Desciption	Vendor	Part Number	Qty	Cost
1	LIDAR Lite	sparkfun.com	SEN-13167	1	$89.95
2	SJOne Board	SCE		1	$80.00
3	I2C Diff Buffer	NXP	PCA9615DPJ	2	$2.99
4	CAN Trasceiver	Philips	TJA1050T	1	$1.03
5	12V-5V DC-DC REG	Murata	7805SR-C	1	$9.90
6	3.3V LDO REG	ON Semiconductor	NCP4683DSQ33T1G	1	$0.92
7	Prototype board	Twin Industries	800-45	1	$12.99
8	Bluetooth Module	Sparkfun	RN41-XV	1	$29.99

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

The Real Time Break assist hardware consists of the three boards. The SJ-ONE board provides the LPC1758 ARM based CPU with the integrated CAN and I2C interface controllers used for communication. The second board referred as “Board #1” in the hardware diagram provides the CAN PHY, 12V to 5V voltage regulation and the I2C differential driver. The third board is located in the front of the car and provides power and proper I2C connectivity to the Linder laser distance sensor. The user interface is implemented through an android based device that connects to the SJ-ONE board through a Bluetooth module.

Hardware Diagram

Hardware Interface

Interface to Lidar Laser Distance Sensor

The Linder laser distance sensor requires 5V and I2C interface operating at a maximum rate of 100Kbps for communication. To provide a reliable and low cost communication to the sensor, a PCA9615 differential driver was chosen. The PCA9615 provides the noise immunity and capability to drive long cables necessary for this application. For cable connectivity, a standard CAT5 RJ45 cable was used because of its low cost and twisted pair connectivity for differential signals. The diagram below shows the connectivity of the differential pairs. In order to provide the maximum differential swing, VDDB1 and VDDB2 should be connected to 5V and use 120ohms for R1 and 60 ohms for R2. VDDA1 and VDDA2 should be pulled up to 3.3V as required by the I2C interface. The PCA9615 provides separate voltage pins for the I2C interface which should be 3.3V and for the differential signaling which should be 5V.

The RJ45 cable and connections should be selected so that each of the differential signals is connected to a corresponding twisted pair. Also, 5V power and ground should be connected so that they use a twisted pair and therefore keep the capacitive coupling through the cabling. The figure below shows the RJ45 pin assignment, as well as the twisted pair cable coloring found in traditional CAT5 cables.

CAN interface to OBDII Connector

Bluetooth/Android Bridge

-interface -hardware -testing methodology

Software Design

-firmware high level design -android high level design -android UI 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.

Implementation

-steps to communicate to bluetooth/android bridge -steps to communicate to OBDII/CAN -braking Algorithm 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

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Include sub-sections that list out a problem and solution, such as:

Issues Found

CAN Broadcast Address

The broadcast address of 0x7DF referred on the Wikipedia (http://en.wikipedia.org/wiki/OBD-II_PIDs) is for 11 bit communication and is outdated. This broadcast address does not work. We could not find information on broadcast address for 29 bit communication. To bypass this blocking issue, we used an OBDII reader and examined what it was sending to find the particular broadcast and response address of our test cars.

Flooding of CAN Messages (TBD)

After establishing communication with the car, we noticed that we were receiving only a couple of replies from the car. This appears to be due to the fact that we do not have the hardware filter implemented. The CAN controller is flooded with messages from the car and is dropping most of the packets. We are currently investigating how to implement the hardware filter.

Conclusion

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Project Video

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Project Source Code

Sourceforge Source Code Link

References

Acknowledgement

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References Used

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Appendix

CAN Transceiver File:S15 244 Grp9 TJA1050.pdf
I2C Differential Buffer File:S15 244 Grp9 PCA9615.pdf
Laser Distance Sensor File:S15 244 Grp9 Laser.pdf

@@ Line 268: / Line 268: @@
 == CAN interface to OBDII Connector ==
+[[File:S15 244 Grp9 CAN.jpg]]
 == Bluetooth/Android Bridge ==