F14: Team4-Self Driving Car - AUG

Introduction

This project is aimed at developing a 1/10 RC car with a self-driving capability based on controller interaction over the CAN (Controller Area Network) bus. With the advent of driverless cars, we felt the need to develop a scaled-down version that can maneuver itself through co-ordinates fed by Google maps and correct its course when it sees an obstacle. To achieve this objective, we plan to integrate 6 controllers dedicated to specific roles that can pass messages over a common CAN communication bus. In addition, the prototype would involve an Android mobile application for data monitoring and controlling purpose to keep a track of the car remotely and feed it the required checkpoints to reach its destination. The car would comprise of three modes of operation namely; home, map and free run. In the home mode, the car would be guided to its home destination (which is preset to Boccardo Business center) from its current location. In the map mode, the user can feed in the desired destination through the google maps interface which the car would follow based on the co-ordinates and heading provided by its GPS and compass respectively. The free run mode will convert the mobile phone into a remote device capable of controlling the speed and direction of the car based on the accelerometer and gyroscope enabled on the device. In this way, the user can take control of the car at any given time. Below is the high-level block diagram of the entire system.

Startup

The following series of events would take place when the car is powered on:

1. The GPS would wait for a satellite fix of at least 3 satellites, which would relay the information to the Android device through its controller over the CAN bus.
   
2. If the user selects the Map mode, he would be required to enter the co-ordinates of the destination visually by dropping a marker on the map.
   
3. The app would compute the checkpoints and distance and feed the information to the on-board communication controller.
   
4. The first checkpoint is sent to the GPS and master controller, which would co-ordinate the events for the motor and sensor controllers.
   
5. Any obstacle detected by the ultrasonic sensors would override the current path and try to avoid the obstacle.
   
6. The master controller would compute the course correction and reconfigure the required controllers once the car has passed the obstacle.
   
7. The IO controller is responsible for monitoring the data on the CAN bus and displaying the information on the mounted LCD panel. The light and battery sensors are also connected to the IO controller, which automatically turn on the headlights and monitor the battery health respectively.
   
8. Start/Stop triggers can be given to the car remotely using the mobile application as well as from the on-board LCD.
   
9. Once the car reaches the first checkpoint, it will request for the second one from the communication controller and pass it over to the master. In this way, the process continues till the car reaches the destination.
   
10. Home mode operates in a similar way but with a fixed destination and the free run mode is pretty much self-explanatory
    

Highlights

1. Self-Navigation with Obstacle avoidance on all sides on the car.
   
2. Google maps interface for location monitoring and destination setting along with checkpoint computation.
   
3. Three modes of operation – Home, Map and Free run.
   
4. Three choices of speed – Slow (8 mph), Normal (10 mph) and Turbo (12 mph).
   
5. Automatic checkpoint detection and request for checkpoint system.
   
6. Headlights using lights sensors and brake lights on the tail.
   
7. Battery health monitoring.
   
8. Visual picturization of sensor data relative the car on the android application.
   
9. Speed gauge and compass needle for easier visualization on the application.
   
10. Kill switch for instant power off.
    
11. Free run mode for remotely controlling the car.
    

Team Members & Responsibilities

• Sensor Controller:
  • Chinmay Vaidya
    
  • Manuj Shinkar
    
• Motor Controller
  • Viral Agrawal
    
  • Mitesh Sanghvi
    
• I/O Unit:
  • Tej Kogekar
  • Mayur Salve
    
• Communication Bridge + Android:
  • Jayanth Nallapothula
    
  • Manish Mandalik
    
  • Kwun Fung Ng (Daniel)
    
• Geographical Controller:
  • Ishan Bhavsar
    
  • Tanuj Chirimar
    
  • Sushant Potdar
    
• Master Controller:
  • Dhaval Parikh
    
  • Harita Dhiren Parekh
    
  • Rutwik Kulkarni
    

Parts List & Cost

S.R.	Description	Manufacturer	Part Number	Qty	Total Cost
1	SJOne Board	-	-	6	$480.00
2	RC Car	Traxxas	-	1	$240.00
3	Ultrasonic Sensor	Parallax	28015	3	$69.00
4	ADC Sensor	Maxbotix	MB1000	1	$29.00
5	LDR	-	-	1	$1.00
6	Battery Health Monitoring Resistors	-	-	2	$2.00
7	IR Sensor (Used as Speed Encoder)	-	-	1	$15.00
8	GLCD with Touchscreen	4D Systems	uLCD-32PTU	1	$106.00
9	Tact Switches	-	-	4	$2.00
10	LEDs with Holders	-	-	4	$2.00
11	XBee Module	Digi	XBee Series1	2	$40.00
12	Bluetooth Module	Microchip	RN42XVP-I/RM	1	$20.00
13	GPS Module	Sparkfun	GPS-11058	1	$49.95
14	Compass Module	Adafruit	HMC5883L	1	$9.95.00
15	CAN Transceiver (Free Samples)	Microchip	MCP2551	6	$0.00
16	Linear Voltage Regulator (Free Sample)	LT	LT1083-5	1	$0.00
17	Miscellaneous	-	-	-	$20.00
	Total (Excluding Shipping and Taxes				$0000.00

Design & Implementation

CAN 11-bit ID Format

MSG	DST	SRC
5 bits (11-6)	3 bits (5-3)	3 bits (2-0)

Controller ID Table

Controller ID	Controller Type
001	Motor Controller
010	Master Controller
011	Sensor Controller
100	GEO Controller
110	Communication Bridge + Android Controller
111	I/O Controller

Controller Communication Table

Master Controller Communication Table

S.R.	Message Number	Destination	Message Name (MSG_FUNCTION)	Data Layout of Data Sent over CAN (byte[0] = total number of data bytes)
1	0x042	All	RESET	NO DATA
2	0x082	All	POWERUP_SYN	NO DATA
3	0x102	All	POWERUP_ACK	Msg1 : byte[1]  : (uint8_t) version Msg1 : byte[2-3] : (uint16_t) year Msg1 : byte[4]  : (uint8_t) month Msg1 : byte[5]  : (uint8_t) date Msg1 : byte[6]  : (uint8_t) dayofweek Msg1 : byte[7]  : (uint8_t) hour Msg2 : byte[1]  : (uint8_t) minute Msg2 : byte[2]  : (uint8_t) second
4	0x142	All	HEARTBEAT	Msg1 : byte[1-2] : (uint16_t) rx_count Msg1 : byte[3-4] : (uint16_t) rx_bytes Msg1 : byte[5-6] : (uint16_t) tx_count Msg1 : byte[7]  : (uint16_t) tx_bytes Msg2 : byte[1]  : (uint16_t) tx_bytes
5	0x3CA	Motor	SPEED_DIR_COMMAND	Msg1 : byte[1]  : (uint8_t) speed Msg1 : byte[2]  : (uint8_t) direction Msg1 : byte[3]  : (uint8_t) brake

Motor Controller Communication Table

S.R.	Message Number	Destination	Message Name (MSG_FUNCTION)	Data Layout of Data Sent over CAN (byte[0] = total number of data bytes)
1	0x0D1	Master	POWERUP_SYN_ACK	Msg1 : byte[1]  : (uint8_t) version
2	0x191	Master	HEARTBEAT_ACK	Msg1 : byte[1-2] : (uint16_t) rx_count Msg1 : byte[3-4] : (uint16_t) rx_bytes Msg1 : byte[5-6] : (uint16_t) tx_count Msg1 : byte[7]  : (uint16_t) tx_bytes Msg2 : byte[1]  : (uint16_t) tx_bytes
3	0x341	Master, I/O and Communication Bridge	SPEED_ENCODER_DATA	Msg1 : byte[1]  : (uint8_t) speed Msg1 : byte[2]  : (uint8_t) dir Msg1 : byte[3]  : (uint8_t) brake

GEO Controller Communication Table

S.R.	Message Number	Destination	Message Name (MSG_FUNCTION)	Data Layout of Data Sent over CAN (byte[0] = total number of data bytes)
1	0x0D4	Master	POWERUP_SYN_ACK	Msg1 : byte[1]  : (uint8_t) version
2	0x194	Master	HEARTBEAT_ACK	Msg1 : byte[1-2] : (uint16_t) rx_count Msg1 : byte[3-4] : (uint16_t) rx_bytes Msg1 : byte[5-6] : (uint16_t) tx_count Msg1 : byte[7]  : (uint16_t) tx_bytes Msg2 : byte[1]  : (uint16_t) tx_bytes
3	0x384	Master, I/O and Communication	GEO_HEADING_DATA	Msg1 : byte[1]  : (uint8_t) current_angle Msg1 : byte[2]  : (uint8_t) desired_angle Msg1 : byte[3]  : (uint8_t) destination_reached Msg1 : byte[4]  : (uint8_t) is_valid
4	0x484	I/O and Communication Bridge	GEO_LOCATION_DATA	Msg1 : byte[1-4] : (float) latitude Msg1 : byte[5-7] : (float) longitude Msg2 : byte[1]  : (float) longitude Msg2 : byte[2-3] : (uint16_t) dist_to_final_destination Msg2 : byte[4-5] : (uint16_t) dist_to_next_checkpoint Msg2 : byte[6]  : (uint8_t) is_valid
5	0x2AC	Communication Bridge	CHECKPOINT_REQUEST	Msg1 : byte[1]  : (uint8_t) checkpoint_num

Communication Bridge + Android Controller Communication Table

S.R.	Message Number	Destination	Message Name (MSG_FUNCTION)	Data Layout of Data Sent over CAN (byte[0] = total number of data bytes)
1	0x0D5	Master	POWERUP_SYN_ACK	Msg1 : byte[1]  : (uint8_t) version
2	0x195	Master	HEARTBEAT_ACK	Msg1 : byte[1-2] : (uint16_t) rx_count Msg1 : byte[3-4] : (uint16_t) rx_bytes Msg1 : byte[5-6] : (uint16_t) tx_count Msg1 : byte[7]  : (uint16_t) tx_bytes Msg2 : byte[1]  : (uint16_t) tx_bytes
3	0x1D5	Master and I/O	CAR_PAUSE	NO DATA
4	0x215	Master and I/O	CAR_RESUME	NO DATA
5	0x425	Geographical	CHECKPOINT_DATA	Msg1 : byte[1-4] : (float) latitude Msg1 : byte[5-7] : (float) longitude Msg2 : byte[1]  : (float) longitude Msg2 : byte[2-3] : (uint16_t) total_distance Msg2 : byte[4]  : (uint8_t) checkpoint_num Msg2 : byte[5]  : (uint8_t) is_new_route Msg2 : byte[6]  : (uint8_t) is_final_checkpoint
6	0x2C5	Master, I/O, Communication Bridge and Motor	DRIVE_MODE	Msg1 : byte[1]  : (uint8_t) mode
7	0x255	Master	FREE_RUN_DIR	Msg1 : byte[1]  : (uint8_t) speed Msg1 : byte[2]  : (uint8_t) turn Msg1 : byte[3]  : (uint8_t) direction

Sensor Controller Communication Table

S.R.	Message Number	Destination	Message Name (MSG_FUNCTION)	Data Layout of Data Sent over CAN (byte[0] = total number of data bytes)
1	0x0D3	Master	POWERUP_SYN_ACK	Msg1 : byte[1]  : (uint8_t) version
2	0x193	Master	HEARTBEAT_ACK	Msg1 : byte[1-2] : (uint16_t) rx_count Msg1 : byte[3-4] : (uint16_t) rx_bytes Msg1 : byte[5-6] : (uint16_t) tx_count Msg1 : byte[7]  : (uint16_t) tx_bytes Msg2 : byte[1]  : (uint16_t) tx_bytes
3	0x303	Master, I/O and Communication Bridge	DIST_SENSOR_DATA	Msg1 : byte[1]  : (uint8t) left Msg1 : byte[2]  : (uint8t) middle Msg1 : byte[3]  : (uint8t) right Msg1 : byte[4]  : (uint8t) back
4	0x443	I/O and Communication Bridge	OTHER_SENSOR_DATA	Msg1 : byte[1]  : (uint8t) battery Msg1 : byte[2]  : (uint8t) light

I/O Controller Communication Table

S.R.	Message Number	Destination	Message Name (MSG_FUNCTION)	Data Layout of Data Sent over CAN (byte[0] = total number of data bytes)
1	0x056	Master	RESET	NO DATA
2	0x0D6	Master	POWERUP_SYN_ACK	Msg1 : byte[1]  : (uint8_t) version
3	0x196	Master	HEARTBEAT_ACK	Msg1 : byte[1-2] : (uint16_t) rx_count Msg1 : byte[3-4] : (uint16_t) rx_bytes Msg1 : byte[5-6] : (uint16_t) tx_count Msg1 : byte[7]  : (uint16_t) tx_bytes Msg2 : byte[1]  : (uint16_t) tx_bytes
4	0x1D4	Master and I/O	CAR_PAUSE	NO DATA
5	0x214	Master and I/O	CAR_RESUME	NO DATA
6	0x2C4	Master, I/O and Motor	DRIVE_MODE	Msg1 : byte[1]  : (uint8_t) mode

Sensor Controller

The sensor board continuously computes various sensor values and sends these values to other controllers. The master controller uses these values to take decisions. The I/O controller displays some of the sensor values. The sensors which are interfaced to the board are:

• Distance sensors
• Light sensor
• Battery sensor

Two type of ultrasonic distance sensors are used. Three PING ultrasonic distance sensors are at the front (left,center and right) and one LV-MaxSonar-EZ0 ultrasonic sensor at the back. The values of these sensors are continuously sent to the master. Based on these values the master controller makes the computations to avoid obstacles. A light dependent resistor(LDR) is used for sensing the ambient light. The values are continuously sent to the I/O controller. According to these values the I/O controller changes the intensity of headlights.

A voltage divider circuit is used to get the battery voltage. The percentage of battery remaining is computed and sent to the I/O controller. The I/O controller displays the battery percentage on the LCD. The onboard 3-axis accelerometer is used to obtain the orientation characteristics of the car. The values obtained for X-axis, Y-axis and Z-axis are sent to the I/O controller. The I/O controller displays these values on the LCD. Depending upon these values, we determine the inclination of the terrain on which the car is running.

Distance Sensor

The obstacle detection is done using 2 type of sensors which are PING ultrasonic distance sensor (Three are used in the front) and LV-MaxSonar-EZ0 ultrasonic sensor which is used at the back.

Figurex: PING Ultrasonic Sensor

Figurex: ADC Sensor LV-MaxSonar-EZ0

Figurex: Working of Ultrasonic Sensor

Figurex: System Block Diagram

Figurex: Flowchart

PING Ultrasonic Distance Sensor: A single I/O pin is used to trigger an ultrasonic burst (well above human hearing) and then "listen" for the echo return pulse. The sensor measures the time required for the echo return, and returns this value to the microcontroller as a variable-width pulse via the same I/O pin.
Some key features of this sensor are:

Provides precise, non-contact distance measurements with a 2 cm to 3m range. Simple pulse in/pulse out communication requires just one I/O pin. Ultrasonic measurements work in any lighting condition, making this a good choice to supplement infrared object detectors. Details: Narrow acceptance angle Range: approximately 1 inch to 10 feet (2 cm to 3 m) 3-pin male header with 0.1" spacing Power requirements: +5 VDC; 35 mA active Communication: positive TTL pulse Dimensions: 0.81 x 1.8 x 0.6 in (22 x 46 x 16 mm) Operating temperature range: +32 to +158 °F (0 to +70 °C)

Figurex: Timing Diagram

Software Design

We need a trigger function and an echo function for the sensor in order to obtain the distance values. The trigger signal is given by keeping the gpio as High for 5 micro seconds and then making it low. Then we configure the same pin as input from the echo and then the function waits for data from the echo pulse. The data reception was queued so that the triggers from all of the sensors do not overlap and create errors in the distance values.

A callback function is used in order to obtain the duration of the echo pulse.Also, there has to be a delay of 750 microseconds between trigger and echo pulse according to the datasheet in order to obtain correct sensor values. Further, we obtain the distance using the formula Distance = (systime_center-750)/75.

LV-MaxSonar-EZ0 ultrasonic sensor uses an ADC interface for providing the sensor values.We configure the pin P1.30 as adc using the bit manipulation. Then we can read the current sensor values using adc0_get_reading function.

For the battery sensor and Light sensor, we use the circuits as shown in the figure. The reading from the circuit is directly taken to the adc pin and calibrated according the requirements.

Depending on the ambient light the table shows some of the ADC readings of the light sensor circuit. Since the ADC is 12 bit, so it can give a maximum value of 4096. The formula used for getting the light percentage from the ADC reading is Light_Percent = (ADC_reading/4096)*100. The on-board Light sensor on the SJone board can be used directly to obtain the light parameter values but the boards are not directly exposed to the ambient light because of the car cover, so a light dependent resistor(LDR) is used. The property of an LDR is that the value of resistance varies according to the light falling on it. The voltage across the LDR is computed using the onboard ADC pin. The resistance R1 is used to prevent short circuit if the LDR values becomes very low.

S.R. ADC Reading Light Percent 1 4096 100 2 3686 90 3 3276 80 4 2867 70 5 2457 60 6 2048 50 7 1638 40 8 1228 30 9 819 20 10 409 10 Tablex: Light Sensor Readings

Using a voltage divider circuit the battery is connected on an ADC pin. The battery voltage on the ADC pin is calculated using the formula battery_voltage_pin = (ADC_reading/4096)*3.3 The battery percentage is calculated in the intervals of 10. We compare the battery voltage on pin to 10 different zones and calculate the percentage of battery remaining. We noticed that for 8.4V battery which is the maximum battery voltage, we get 2.75V on the ADC pin. And for the minimum value on which the car operates we get 2.30V on the ADC pin. In order to get the battery health a simple voltage divider circuit is designed to read the voltage from the battery. The voltage across the 10k resistor is given to the ADC pin of the board.The maximum battery voltage is 9.6 V. The ADC reading corresponding to this voltage is the maximum. Then the readings are compared with the maximum battery ADC reading to get the battery health percentage.

S.R. ADC Reading Battery Voltage on ADC Pin Battery Percentage 1 3413 2.75 100 2 3351 2.70 90 3 3289 2.65 80 4 3227 2.60 70 5 3165 2.55 60 6 3103 2.50 50 7 3040 2.45 40 8 2978 2.40 30 9 2916 2.35 20 10 2854 2.30 10 Tablex: Battery Sensor Readings

Figurex: Battery Sensor Circuit

Challenges and Learnings

1. Limited ADC ports on SJOne Board:
All the sensors have to be a single board in order to have a good design. We should not use other board just to control one sensor. Initially we were planning to use LV-MaxSonar-EZ0 ultrasonic sensor for front as well as back. Light sensor and battery sensor also require ADC port. So overall we needed 6 ADC ports but there are only three ADC pins on the SJ One board. So, instead of using the ADC pins from other boards we changed out design and used three ultrasonic PING sensors in the front which do not require ADC pins.

2. Accuracy of Sensors:
The sensors are reading and sending values to the master at a very fast rate. We observed that sometimes the sensors will give a garbage value in between. We don’t want the master to take the decision on that single reading. So we used a cleaning algorithm that basically averages the values of some readings and send the averaged value to the master. In this way the error difference is reduced.

Motor Controller

Hardware Design

<p align="justify"> The main components of the motor controller hardware are DC motor, Servo motor, Electronic Speed Controller(ESC) and IR sensor. The external battery of 8.4V is used to power up the DC motor via ESC.

Figure1: System Block Diagram

We use Pulse Width Modulation (PWM) signals used to control the DC motor and Servo motor. The PWM signal is given through the PWM pin P2.1 and P2.2 of the SJ-One board. The output of the IR sensor is taken at the GPIO pin P0.26. Voltage required to drive the servo motor is given through the 3.3V Vcc of the SJOne board. The ground of all the components is connected with the GND pin of SJOne board to form a common ground.

Electronic Speed Controller (ESC)

The RC car came with a pre-installed ESC (electronic speed controller), the Velineon VXL-3s which contains an inbuilt circuitry to control the movement and speed of the motors. This was the trickiest part as we had to debug the working of this circuitry and control the working of the motors with the help of PWM value given from the SJOne board. To debug and intercept the signals going to and from the ESC we used a logic analyzer. The wires from the servo and ESC is connected to a motor controller circuit which is generating the required PWM according to the input from the wireless remote. The circuit has four channels out of which ESC is connected at channel 2 and servo motor is connected at channel 4.

Figurex: Electronic Speed Controller

Figurex: Motor Controller Circuit Connection

To debug the ESC we connect logic analyzer at GND pin and speed control pin. We do not move the speed trigger of the wireless remote and notice that the motor controller circuit is sending some initialize pulse of duty cycle 15.05% to initialize the ESC.

Figurex: Initial Sequence to Initialize the ESC

For maximum reverse speed the motor controller circuit is sending duty cycle of 10.07% to ESC. So the DC motor has the reverse duty cycle range from 15.05% – 10.07%, but due to the weight of the car for us the initial reverse duty cycle is 14.20%.

Figurex: Maximum Reverse Duty Cycle (10.07%)

To determine the duty cycle range for the servo motor we connected the logic analyzer at GND and turn control pin of the servo motor. For straight the servo duty cycle we see on the logic analyzer is 15.39%

Figurex: Servo Straight Duty Cycle (15.39%)

For maximum full right of the servo motor, the motor controller circuit is sending duty cycle of 20.03% to ESC. So the servo motor has the straight to full right duty cycle range from 15.39% – 20.03%.

Figurex: Servo Full Right Duty Cycle (20.03%)

For maximum full left of the servo motor, the motor controller circuit is sending duty cycle of 10.41% to ESC. So the servo motor has the straight to full left duty cycle range from 15.39% – 10.41%.

Figurex: Servo Full Left Duty Cycle (10.41%)

DC Motor

Our car came installed with the Velineon 3500 Brushless motor. The motor needs 8.4V of power supply to work. This motor has the power to run the car at the maximum speed of the 35mph. The table below contains information about PWM (duty cycle) given to the motor and the corresponding speed of the car on the flat surface. S.R. Duty Cycle Speed(mph) 1 15.80 2 2 16.00 4 3 16.20 6 4 16.40 8 5 16.60 10 6 16.80 11 Tablex: DC Motor Duty Cycle v/s Speed

Figurex: DC Motor

DC motor is controlled with the help of three wires coming out of the ESC. The wires are Vcc, Gnd and Speed control. The Vcc is not used as required voltage is directly given to motor through battery via ESC. The Gnd is connected with Gnd pin and Speed control is connected to the PWM pin of SJOne board. S.R. ESC Wire Pins SJOne Board Pins 1 Vcc - 2 GND GND 3 Speed Control P2.1 Tablex: DC Motor Pin Connections For DC motor we are using pwm2 i.e. pin P2.1 of the SJOne board, the pwm function is the in-build function which requires two parameters, one is pwm that we are using and the second parameter is the frequency of the pwm. To set the duty cycle in-build set function is used in which we are passing the duty cycle at which we want DC motor to work.

Figurex: DC Motor

Servo Motor

Our car came with waterproof digital servo motor (Traxxas part 2075). This motor works without ESC. We can directly control this motor by giving PWM signal from our SJOne board. The below table contains information about PWM (duty cycle) given to the motor and the corresponding turns taken by the car. S.R. Duty Cycle Turn 1 10.41 Full Left 2 12.35 Half Left 3 13.53 Slight Left 4 15.39 Straight 5 16.00 Slight Right 6 17.37 Half Right 7 20.03 Full Right Tablex: Servo Motor Duty Cycle v/s Turn

Figurex: Servo Motor

Servo motor is controlled with the help of three wires coming out of the servo motor. The wires are Vcc, Gnd and Direction control. The Vcc is connected to the 3.3v, Gnd is connected with Gnd pin and direction control is connected to the pwm pin of SJOne board. S.R. Servo Motor Pins SJOne Board Pins 1 Vcc Vcc 2 GND GND 3 Direction Control P2.2 Tablex: Servo Motor Pin Connections For Servo motor we are using pwm3 i.e. pin P2.2 of the SJOne board, the pwm function is the in-build function which requires two parameters, one is pwm that we are using and the second parameter is the frequency of the pwm. To set the duty cycle in-build set function is used in which we are passing the duty cycle at which we want servo motor to work.

Figurex: DC Motor

Speed Sensor

To calculate the speed of the car we interfaced an IR sensor on the inner back left wheel of the car. We have attached the IR sensor on the inner surface of the wheel which is reflective, so we attach a black rubber on the wheel which acts as a non-reflective object. The IR sensor code will count the number of times the transmitted wave is not received back. Based on the total count we determine the real time speed of the car. Working of IR Sensor: The IR sensor send the transmitted wave, if the object is reflective than the sensor will receive the reflected wave but if the object is non-reflective i.e. of black color than sensor will not receive the reflected wave as the non-reflective surface will absorb the transmitted wave.

For sensor the inner surface of the wheel is reflecting so we stick a black piece of rubber on it which will not get reflected. This will allow us to determine when wheel will complete one rotation. Three wires are coming out of the sensor. The wires are Vcc, Gnd and Signal. The signal pin is connected to the GPIO pin of the SJOne board through which we are reading the output of the sensor. S.R. IR Sensor Pins SJOne Board Pins 1 Vcc Vcc 2 GND GND 3 Signal P0.26 Tablex: IR Sensor Pin Connections

Figurex: IR Sensor attached to Wheel

To send and receive signal from the IR sensor we have interfaced the signal pin of the IR sensor at the GPIO pin P0.26 of the SJOne board. The ext_callback() is used to get the number of count from the IR sensor. In-build hard timer TIME3_IRQHandler() is used to get the speed of the car using the total count from ext_callback() function, the circumference of the car which in our case is 35cm and the conversion factor of cm to mph.

Communication Bridge + Android Controller

Introduction

The communication bridge is a connection between Android application and other controllers on the RC car. The Android application is written in Java and there are xBee(ZigBee) chip sets along with Bluetooth as a bridge connection. The major functions of the bridge is

1. Allow a user to see sensor values, car speed, etc.
2. Allow a user to select a destination from Google Earth.

Modules

1. xBee Module:
The following pictures shown the chip set of xBee which is using zigbee to communicate with each other:

Figure1:

xBee Chipset

Features: Long Range Data Integrity Indoor/ Urban: up to 100’(30m) Outdoor line-of-sight: up to 300’ (90m) Transmit Power: 1mW(0dBm) Receiver Sensitivity: -92dBm Advanced Networking & Security Retries and Acknowledgements DSSS (Direct Sequence Spread Spectrum) Each direct sequence channels has over 65,000 unique network addresses available Source/ Destination Addressing Unicast & Broadcast Communications Point-to-point, point-to-multipoint and peer-to-peer topologies supported Low Power TX Peak Current: 45mA(@3.3V) RX Current: 50mA(@3.3V) Power-down Current: <10μA ADC and I/O line support Analog-to-digital conversion, Digital I/O Line Passing Easy-to-use Free X-CTU Software AT and APU Command Modes for configuring module parameters

2. Bluetooth Module (RN-421):
The following picture is the Bluetooth module RN-42I:

Figure1: Bluetooth Module RN-421

Features:

• Fully qualified Bluetooth version 2.1 module, support version 2.1+Enhanced Data Rate (EDR)
• Backwards compatible with Bluetooth version 2.0, 1.2 and 1.1.
• Low power (26uA sleep, 3mA connected, 30mA transmit)
• UART (SPP or HCL) and USB (HCI only) data connection interfaces.
• Sustained SPP data rates: 240 Kbps (slave), 300Kbps (master)
• HCI data rates: 1.5 Mbps sustained, 2.0Mbps burst in HCI mode
• Bluetooth SIG certified
• Castellated SMT pads for easy and reliable PCB mounting
• Certifications: FCC, ICS, CE

Interface

1. xBee:
Communication setup:

Since we are not connecting the xBee directly to our computer to work on the configuration and we have to connect it through using the SJ One board with UART communication pins. Thus, we have to initially set the baud rate at 115200. On xBee chip set, there are 20 pins including VCC and GND. In our design of the communication bridge, we just need four of them including VCC (Pin1), GND(Pin10), Data Out(Pin2), and Data In (Pin3). For xBee chip set connected with Bluetooth module, VCC is connected to SJ One board VCC out as well as GND. For Data out on xBee, it is connected UART 2 Rx(Pin49) and Data in connected to UART Tx(Pin50). For xBee chip set connected to car SJ One board, we can directly place it on xBee connect pins on SJ One board.

Figurex: Pinout of xBee

Figurex: UART2 pins of SJOne Board

Pairing:

In order to let the xBee pair to communicate to each other, we have to set both xBee chip sets have the same PAN ID. The xBee has factory default setting that we just have to input default commands for viewing or changing the setting on chips. Some of major commands show as following:

Table1: Commands of xBee

Since we are using SJ One board to connect with the xBee chip sets, so we have decided to implement commands inside the FreeRTOS program. In the implementation, we have included the following logic to pair the xBee chip sets. Steps of pairing xBee chip set:

• Checking both xBee chip sets are working with “AT” command and it will return “OK” for working
• Checking and changing PAN ID on either one xBee to match with another and the PAN ID are usually 4 digits numbers. “ATID” is the command to check and change the ID
• Checking and changing the destination address for both xBee chip sets. The address of chip sets are printed on the bottom of the xBee.

2. Bridge between xBee and bluetooth:

Since xBee cannot communicate with regular android cell phone, we would need one device/module that common accepted for both configurations. Bluetooth is one of the best devices for this purpose. In order to create a platform for these two device (Bluetooth and xBee), SJ One board has been used as the medium to make communication bridge them. On the SJ One board, we have chosen UART 2 as communication connector among UART 2 or UART 3. There is no logic stored on the SJ One board but the initialization for the UART port. The logic for the communication for Bluetooth and xBee module is simple. The baud rate has to set to 115200 for both module Tx of Bluetooth has to connect with Tx of xBee while Rx of Bluetooth has to connect with Rx of xBee. Besides, both Vcc(3.3V) and Ground of Bluetooth module and xBee module are connected to the Vcc and ground on SJ One board respectively.

Figurex: Top View of Bridge

Figurex: Circuit Diagram

Figurex: System Block Diagram

3. Bluetooth:

Bluetooth module is providing a connection for Android device and xBee. There is no initialization such as initializing Pan ID on xBee on the Bluetooth module but the Android device side. For the first time connection between Android device and the Bluetooth module, we need to pair them. In the Bluetooth device searching section (Setting -> Bluetooth) of the Android device, we can see the Bluetooth module name e.g.RNBT-99EE. In order to pair them, there is a default pass code (0000 or 1234) to enter from the Android device.

Figurex: Bluetooth Module

Figurex: Pinout of RN-42

Android Application

The Android Application is connected to the car through the Bluetooth-xbee interface. The first point of contact for the application is the Bluetooth module for which a separate class was written which connects using sockets based on the UUID (Universally Unique Identifier) and pairing history of the device running the code.

Figurex: Sample Code

This snippet would get the UUID for connecting to a Bluetooth serial board that is a well-known UUID. If we were using an Android peer, we would have created our own unique UUID.

Figurex: Sample Code

Just like socket programming, we create output and input streams for the data and close the sockets once the connection has ended. The simplest way to open a Bluetooth socket is by opening a BluetoothSocket for communication with the remote device, using createRfcommSocketToServiceRecord (UUID) as shown above. The application has been configured such that the user cannot go past the connectivity page until the Bluetooth of the android has connected to the module. This ensures that there’s no false sending/receiving of data and does not lead to the user to believe the data has been sent without actually connecting. The connectivity page is shown below:

Figurex: Bluetooth Login

Figurex: Successfully Connected

Figurex: Map

The android application has been divided into 3 views (rather Activities) to visualize the following:

1. A Google maps view show the route and current location

In this Activity, the user can drop a pin at any point and request for a route from the Google maps API which would send back a response in the JSON format. Upon parsing, the checkpoints are extracted and plotted on the map fragment. Upon completion, all checkpoints are sent to the communication module in the following format:
g37.34252,-121.12234,37.636423,-121.76543,350$
‘g’ stands for geo data that the lpc module recognizes and stores the lat-long values that follow. The last value in the string is the total distance from the source to the destination. The ‘$’ termination is used as a common two-way message termination character. Even when any messages on the CAN bus are sent to the android application, they are sent with a ‘$’ termination. On top of each view of the application, the user can select the drive mode, start/stop the car and select the drive speed. This brings about ease of use and uniformity to the application. The current location is plotted and shown with a blue dot which changes dynamically based on the location fed by the GPS controller on the bus. All locations and checkpoints are displayed using the Marker object of the Android API.

2. A Dashboard view to translate the numeric values of all the sensors into a visual depiction of the speed gauge, compass, sensors and motion of the car

This Activity is the home Activity which is the default activity for the application. A lot of information is conveyed as a dashboard on an actual car. For e.g. the analog speedometer rotates the needle from 0-12, which is its high speed. The compass next to the speedometer shows the current heading of the car with respect to magnetic North. The sensor value representation has been inspired from the BMW parking assist which shows color coded zones based on the distance from the sensors. As the distance from the obstacle increases, more colors are visible until an infinity point when no colors are seen. When a red is seen next to the respective sensor, the car cannot proceed in that direction. This gives the user a clear understanding of the status of the car. Below is the chart for the color vs. zone: S.R. Zone Color 1 0-3 Red 2 4-6 Red + Orange 3 7-9 Red + Orange + Yellow 4 10-11 Green 5 >11 All Invisible

Figurex: Current Sensor Readings, Speed, Obstacles etc.

The road shown in the background is in fact a dynamic background that changes as per the speed of the car. For this, Frame Animation was used which sliced one image into 4 and repeated these frames at different speeds based on the actual speed of the car. In short, the background will move when the car moves and stop when the car halts.

</p> 3. Informational view displaying all the data in a tabular format for debugging purposes

Finally, this view shows all the Raw information that the Bluetooth controller intercepts on the CAN bus. It shows the following information: Battery % Speed in mph Light sensor % value All distance sensors data namely left, center, right and back Geo data: Current heading, latitude and longitude. CAN bus and controller information: Bus utilization in bps and %, Tx and Rx counts of all controllers along with their status’ i.e. Dead or Alive (Red or Green LED respectively).

Figurex: Status of All SJOne Boards and GPS

This mode is more useful for debugging purpose since it gives the user the understanding if a particular board is up and running or is down and has stopped sending messages on the bus. Below each Activity are navigation icons, which can navigate from any activity to the other since the number of activities is limited to 3. Each activity uses the TimerTask class to update the UI every 200 ms. A snippet of the Timer Task used in the Google maps activity is shown below:

Figurex: Sample Code

The above snippet updates the UI every 200ms without any delay. This makes the app more responsive but power hungry. Since we’re only focused on managing the application and not the general performance of the device, this compromise is reasonable. The application was developed on Android Studio and is compatible with Android devices with screens of 720x1280 pixels or greater and API level 14 or higher (ideally Android 4.4.4).

The format for the messages exchanged between the android application and the controller board can be seen in table:

S.R.	Command	Code
1	Start	"a$"
2	Stop	"b$"
3	Checkpoints	"glat1,long1,lat2,long2$"
4	Mode:
	-Map	"ghome$"
	-Home	"gmap$"
	-Free Run	"f$"
5	Speed:
	-Slow	"s$"
	-Normal	"n$"
	-Turbo	"t$"

Tablex: Receiving Data from Android

S.R.	Command	Code
1	Sensor Values	"s1=left_val, center_val, right_val, back_val$"
2	Speed	"speed=20$"
3	Compass Reading	"heading=5$"
4	Current Location	“geo=lat,long$”
5	Start (from I/O)	“start$”
6	Stop (from I/O)	“stop$”
7	Tx Count (All Controllers)	“txcount=1(ctrl ID),,50(val)$”
8	Rx Count (All Controllers)	“rxcount=1(ctrl ID),50(val)$”
9	CAN Utilization (bps and %)	“con_util=300,20$”
10	Light Sensor (%)	“light=10$”
11	Battery Sensor (%)	“battery=50$”

Tablex: Transmitting Data to Android

Improvement

In order to have some better portable experience with the connection, it is better to have less devices holding on hand when driving the car. Thus, we can swap the Bluetooth/xBee bridge to BluetoothBee module and so we don’t need to use the SJ One board as a medium/ platform.

The second enhancement is on the Android application which we may have more functions such as controlling the light on/off and intensity. Also, it is better that we can have a debugging feature on the Android such as redirect UART 0 to the Android for remote debugging. Time to destination is also a great feature we would like to put it on the application so the user can know how long would it take from starting point to end point.

Testing & Technical Challenges

Module Name	S.R.	Test Case	Test Description	Result
Sensor	1	-	-	-
	2	-	-	-
	3	-	-	-
Motor	1	-	-	-
	2	-	-	-
	3	-	-	-
I/O	1	-	-	-
	2	-	-	-
	3	-	-	-
Communication Bridge+ Android	1	-	-	-
	2	-	-	-
	3	-	-	-
Geographical	1	-	-	-
	2	-	-	-
	3	-	-	-
Master	1	-	-	-
	2	-	-	-
	3	-	-	-

Schedule

Sensor Team Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	09/14/2014	09/20/2014	Understanding the logic of sensors to be used	Completed	09/20/2014
2	09/21/2014	10/04/2014	Writing the codes for the different types of sensors	Completed	10/04/2014
3	10/05/2014	10/11/2014	Testing the different sensors for accuracy and placing the order for the one we have selected.	Completed	10/11/2014
4	10/12/2014	10/25/2014	Build CAN transceiver and send data to the Master Board	Completed	10/25/2014
5	10/26/2014	11/01/2014	Place all the sensors on car and test for obstacle avoidance	Completed	10/28/2014
6	11/02/2014	11/14/2014	Work on light and tilt sensors	Completed	11/04/2014
7	11/15/2014	12/09/2014	Final testing and debugging	Completed	12/19/2014

Motor Team Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	09/14/2014	09/20/2014	Understand the logic of Motor Controller present in the RC Car	Completed	09/20/2014
2	09/21/2014	09/27/2014	Replace on-board controller with SJSU One board	Completed	09/22/2014
3	09/28/2014	10/04/2014	Drive the DC motor with SJSU One board at different Duty Cycles	Completed	09/30/2014
4	10/05/2014	10/11/2014	Test the Servo and DC motor together for moving forward and taking turns	Completed	10/09/2014
5	10/12/2014	10/18/2014	Build CAN Transceiver and move the car as per the CAN message received	Completed	10/13/2014
6	10/19/2014	10/25/2014	Make arrangement for CAN subscription task	Completed	10/25/2014
7	10/26/2014	11/01/2014	Interface encoder and calculate the actual speed at which car is running	Completed	10/28/2014
8	11/02/2014	11/08/2014	Make compensation algorithm and make car to move at desired speed	Completed	11/04/2014
9	11/09/2014	12/09/2014	Final testing and debugging	Completed	12/19/2014

I/O Team Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	09/14/2014	09/20/2014	Search and order GLCD module with touch screen, LEDs for headlights	Completed	09/20/2014
2	09/21/2014	10/04/2014	Study of GLCD data frame formats and design GUI	Completed	10/03/2014
3	10/05/2014	10/11/2014	Development of GLCD functions including touchscreen handler	Completed	10/11/2014
4	10/12/2014	10/25/2014	Setup CAN subscription tasks for communication with Master controller	Completed	10/27/2014
5	10/26/2014	11/01/2014	Develop hardware and code for automatic headlight control.	Completed	11/01/2014
6	11/02/2014	11/14/2014	Build hardware for switches and write interrupt handlers for the same	Completed	11/07/2014
7	11/15/2014	12/09/2014	Mount GLCD, headlights, switches on car and final testing	Completed	12/19/2014

Communication Bridge + Android Team Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	09/14/2014	09/20/2014	Google maps API research	Completed	09/20/2014
2	09/21/2014	10/04/2014	Mock locations on Google maps and simulate co-ordinates w/o gps	Completed	10/04/2014
3	10/05/2014	10/11/2014	Two way Bluetooth communication and setup RTOS tasks	Completed	10/11/2014
4	10/12/2014	10/25/2014	Raw GUI for app and setup CAN tasks for Start and Stop commands	Completed	10/25/2014
5	10/26/2014	11/09/2014	Integration with GEO module and queue for each subscribed service	Completed	11/09/2014
6	11/10/2014	11/16/2014	Incorporate all essential services into Android app and test for response	Completed	11/16/2014
7	11/16/2014	11/23/2014	Final setup and changes for all the CAN tasks along with XBee interfacing	Completed	11/23/2014
8	11/24/2014	12/01/2014	Testing with GEO module with real-time co-ordinates and plotting way points onto Maps	Completed	12/01/2014
9	12/02/2014	12/09/2014	Final Testing and verification of all components on the main field	Completed	12/19/2014

GEO Team Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	09/7/2014	09/14/2014	Market research for GPS and Compass Modules	Completed	09/14/2014
2	09/14/2014	09/21/2014	Place order / receive the modules	Completed	09/20/2014
3	09/21/2014	09/28/2014	Interface GPS with SJ -One board via UART	Completed	09/26/2014
4	09/28/2014	10/05/2014	Interface Compass with SJ-One Board via I2C	Completed	10/03/2014
5	10/05/2014	10/12/2014	Parsing the GPS data stream	Completed	10/11/2014
6	10/12/2014	10/19/2014	Calibration and testing of compass	Completed	10/13/2014
7	10/12/2014	10/19/2014	Decide CAN message ID’s and message formats	Completed	10/28/2014
8	10/19/2014	10/26/2014	Combining UART and GPS parsing. Create task for GPS	Completed	10/25/2014
9	10/19/2014	10/26/2014	Combining compass calibration and i2c interface. Create task for Compass	Completed	10/25/2014
10	10/26/2014	11/02/2014	Distance to Destination Calculation and Algorithm	Completed	11/02/2014
11	11/03/2014	11/10/2014	Basic CAN communication with Master, IO and Android	Completed	11/10/2014
12	11/10/2014	11/17/2014	Synchronization and Data Integrity (Semaphores/Mutex/Critical Section)	Completed	11/17/2014
13	11/18/2014	11/25/2014	Final Integration of CAN Framework and Implementation of CAN communication with other modules	Completed	11/25/2014
14	11/26/2014	12/09/2014	Testing and debugging on car (Re-Calibration/Bug Fixes)	Completed	12/19/2014

Master Team Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	09/7/2014	09/13/2014	Understanding CAN Bus and API's	Completed	09/13/2014
2	09/14/2014	09/20/2014	Deciding System Flow	Completed	09/20/2014
3	09/21/2014	09/27/2014	Deciding MSG id's for all devices	Completed	10/27/2014
4	09/28/2014	10/11/2014	Testing Subscription between 2 devices	Completed	10/4/2014
5	09/28/2014	10/11/2014	Making CAN bus hardware to interface all SJOne boards	Completed	10/11/2014
6	09/28/2014	10/11/2014	Testing subscription and time sync between all devices	Completed	10/11/2014
7	10/12/2014	10/18/2014	Reading sensor data from boards at the subscription rate	Completed	10/26/2014
8	10/19/2014	11/1/2014	Algorithm for obstacle avoidance	Completed	10/27/2014
9	11/2/2014	11/15/2014	Algorithm for GPS based navigation	Completed	11/15/2014
10	11/16/2014	11/22/2014	Initial testing and tweaking of the car	Completed	11/22/2014
11	11/23/2014	12/9/2014	Final Testing! Showdown time!	Completed	12/19/2014

References

Acknowledgement

The hardware components were made available from Amazon, Sparkfun, Adafruit, HSC, Excess Solutions. Thanks to Preetpal Kang for providing right guidance for our project.

References Used

1. LPC_USER_MANUAL
2. Ultrasonic Sensor
3. ADC Sensor
4. GLCD with Touchscreen
5. XBee Module
6. Bluetooth Module
7. GPS Module
8. Compass Module
9. CAN Transceiver
10. Linear Voltage Regulator
11. Socialledge Embedded Systems Wiki
12. Preetpal Kang, Lecture notes of CMPE 243, Computer Engineering, Charles W. Davidson College of Engineering, San Jose State University, Aug-Dec 2014.
13. en.wikipedia.org/