a report on how to connect the OV7670 camera module with arduino microcontroller

1. INTRODUCTION
In this project our aim is to interface OV7670 camera module with ATmega based
Arduino Microcontroller board. Camera modules are widely used in the world of
electronics. Our aim is to show how to connect, configure and get a test image
using a small program on java, it will be an excellent starting point for further
experiments. Currently ov7670 camera is the affordable image acquisition module
for embedded applications.
Our goal is to interface the camera with Arduino which are much
efficient, low cost easily available and easy to configure. These are the major
reasons for which here an Arduino is used. In spite of the following advantages
there are some disadvantages too, that are:
o Very limited I/O pins
o Limited memory capacity
o Slow Processing speed
The above disadvantages are the challenges in interfacing the camera
with an Arduino and these are to be overcome by applying some Data handling
and manipulation techniques. The OV7670 Camera module talks over a modified
I2C protocol that is known as SCCB (Serial Camera Control Bus). This protocol is
intended to be used with OmniVision’s camera modules.
This project is intended to provide a low cost and easily configurable image
capturing solution, that can be used in real-time Time-lapse photography, image
acquisition systems or as security cameras.
The camera module is accessed by SCCB (I2C) protocol by the Arduino.
The Data sent by the camera is parallel over data channel D0-D7, Data received by
the Arduino is sent to the computer over serial communication and this follows the
rule of sending pixel data of one row at a time. This help to overcome the problem
of slow processing and slow data transmission rate of the Arduino boards
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2. Figure 1: Block diagram for Camera-Arduino interface
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OV7670
camera
module
Arduino UNOI2C
COMPUTER Seri
al

3. HARDWARE
2.1 CAMERA MODULE (OV7670)
The camera module has an onboard CMOS sensor designed for mobile application
where low power consumption and small size are of utmost importance.
Proprietary sensor technology utilizes advanced algorithms to cancel Fixed Pattern
Noise (FPN), eliminate smearing, and drastically reduce blooming. All required
camera functions are programmable through the Serial Camera Control Bus
(SCCB) interface.
The device can be programmed to provide image output in various fully
processed and encoded formats.
Resolution
VGA (640 x 480); - QVGA (320 x 240); - CIF (352 x 240); -
QCIF (176 × 144)
Transfer rate up to 30 fps
Image encoding RGB 565/555, YUV / YCbCr 4: 2: 2
Interface I2C interface interaction / SCCB
Table 1: Camera module Specification
2.2 Two Wire SCCB Interface
The modified 2-wire implementation allows for a SCCB master device to interface
with only one Slave device. This 2-wire application is implemented in the camera
chip reduced pin package products where the SCCB_E signal is not available
externally.
Figure 2: Two Wire SCCB Interface
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4. 2.3 Pin Functions
Signal Name Signal Type Description
SCCB_Ea Output Master drives SCCB_E at logical 1
When the bus is idle. Drives at logical 0 when
the master asserts Transmissions or the
system is in Suspend mode.
SIO_C Output Master drives SIO_C at logical 1 when The
bus is idle. Drives at logical 0 and 1 when
SCCB_E is driven At 0. Drives at logical 0
when the system is Suspend mode.
SIO_D I/O Serial I/O Signal 0 Input and Output -
remains floating when the bus is idle and
drives to logical 0 when the system is in
Suspend Mode.
Table-2: Master Device Pin Descriptions
Signal Name Signal Type Description
SCCB_Ea Input Input pad can be shut down when the System
is in Suspend mode.
SIO_C Input Input pad can be shut down when the System
is in Suspend mode.
SIO_D I/O Serial I/O Signal 0 Input and Output - input
pad can be shut down When the system is in
Suspend mode.
Table-3: Slave Device Pin Descriptions
2.4 Application
Some of the applications of camera module are: PC Camera, and Cellular phones,
Video conference equipment, Machine vision, Security camera, Biometrics,
Digital Still Cameras
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5. 2.5 ARDUINO
Arduino is an open-source platform used for building electronics projects. Arduino
consists of both a physical programmable circuit board (often referred to as
a microcontroller) and a piece of software, or IDE (Integrated Development
Environment) that runs on your computer, used to write and upload computer code
to the physical board.
Microcontroller ATmega 328-p
Operating Volts 5V
Input Voltage 7-20v
Digital I/O Pins 14
Analog Input 6
PWM pins 6
Flash Memory 32 Kb
SRAM 2 Kb
EEPROM 1 Kb
Clock Speed 16 MHz
Current 50 mA
DC Current at Digital I/O 20 mA
Table 4: Arduino UNO Specification
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6. CAMERA-ARDUINO INTERFACING CIRCUIT
For interfacing the camera module with the Arduino we need a circuit that will
provide the mount points as well as the voltage Pull-up and Pull-down facilities.
below is a Typical Block representation of the hardware connection between
OV7670 and Arduino UNO. Oscillator used here is optional, we will be Arduino’s
onboard crystal oscillator is being used to generate the XCLK.
3.1 Block diagram for Arduino-Camera interfacing
Arduino
Figure 3: Block representation of Connection
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Camera
Module
SCL, SDA
HREF, VSYNC
DATA
PCLK
PWDN
+3.3V, GND
Oscillator
XCLK

7. 3.2 Pin Configuration
Pin configuration is one of the most important data that must be kept in mind
while designing the interfacing circuit and must be followed to ensure proper
communication Arduino and Camera Module.
Pin Type Description
VDD Supply Power supply
GND Supply Ground level
SDIOC Input SCCB clock
SDIOD Input/output SCCB data
VSYNC Output Vertical synchronization
HREF Output Horizontal synchronization
PCLK Output Pixel clock
XCLK Input System clock
D0-D7 Output Video parallel output
RESET Input Reset (Active low)
PWDN Input Power down (Active high)
Table 5: Arduino Pin Configuration
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8. 3.3 Circuit Diagram
The Arduino is rated for 5V and the camera module is of 3.3V. Hence, the voltage
divider for the XCLK will be used (two resistors of 4.7KΩ) to pull down the
voltage to ~3V. Furthermore, OV7670 does not provide output voltages higher
than 3.3V which is a quite low for Arduino to reads the input as high (5V), so we
will connect pull-up resistors.
Here external signal is provided to D12 to capture image and to D8 for
image to PDF conversion, both are active high with 0.3 sec high pulse.
Figure 4: Circuit Diagram for OV7670-Arduino Interfacing [Source: privateblog.info]
PROGRAM FLOW FOR INTERFACING
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9. OV7670 camera module captures image during LOW at VSYNC and sends out
row data during the HIGH at HREF. The Arduino receives the parallel data input
from camera module image sensor and converts it to the serial data and also
provides initialization to the registers of the OV7670 Module.
Figure 5: Typical Data flow diagram
Basic steps in the code are:
1. Generation of PWM
2. Start I2C Communication
3. Write default register values
4. Receive data from camera
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Arduino

10. Figure 6: Flow diagram for initialization of camera module
4.1 Configure Arduino that will give 8 MHz at Pin D11
DDRB | = (1 << 3); // pin 11,
The ASSR & = ~ (_BV (EXCLK) | _BV (the AS2));
TCCR2A = (1 << COM2A0) | (1 << WGM21) | (1 WGM20 <<);
TCCR2B = (1 << WGM22) | (CS20 1 <<);
OCR2A = 0; // (F_CPU) / (2 * (X + 1))of d0 of low-
DDRC & = ~ 15; // d3 camera
DDRD & = ~ 252; // d7-d4 and interrupt pins
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11. 4.2 Configure I2C interface
TWSR & = ~ 3; // preset for the disable the TWI
TWBR = 72; // set to 100 kHz
Figure 7: Flow Diagram of I2C communication
4.3 Initialization of Camera Module
Figure 8: Write default Register values
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ARDUINO
Write Default register
Values with I2C Camera Module

12. WrReg (0x12, 0x80);
_delay_ms (100);
wrSensorRegs8_8 (ov7670_default_regs);
WrReg (REG_COM10, 32); // PCLK does not HBLANK Locality toggle on.
4.4 Receiving Image bytes
The camera module sends parallel image data bytes where it is buffered till receiving full
row data then this data is sent over serial communication to the pc as shown in figure 9.
Figure 9: Receiving Image Bytes
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OV7670
camera
Module
Arduino UNO
ComputerParallel Data Serial Data
MUX
Buff
er
RAM

13. OV7670 MODULE DATA TRANSFER
The SIO_C signal is a single-directional, active-high, control signal that must be
driven by the master device. It indicates each transmitted bit. The master must
drive SIO_C at logical 1 when the bus is idle. A data transmission starts when
SIO_C is driven at logical 0 after the start of transmission as shown in figure 10 &
11. A logical 1 of SIO_C during a data transmission indicates a single transmitted
bit. Thus, SIO_D can occur only when SIO_C is driven at 0.
5.1 Timing Diagram
Figure 10: SCCB Timing Diagram
Figure 11: Horizontal Timing Diagram
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14. Camera module sends row data between every HSYNC LOW and during each
HSYNC HIGH, the HREF follows the HIGH and both of this occurs between the
two HIGH of the VSYNC signal as shown in figure 12, that means all the row data
is sent over the VSYNC at LOW.
Figure 12: VGA Frame Timing
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15. PIXEL DATA BYTE TO IMAGE CONVERSION
For this purpose a java program is being used, that will grab the serial input data
(bits) stream from Arduino at specific COM port that will generate a valid BMP
image from it , the code works as illustrated below in figure 13.
6.1 Program Work Flow
Figure 13: Algorithm of data to image generation
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16. 6.2 COM Port selection (JAVA)
if(!enumeration.hasMoreElements())
break;
portId = (CommPortIdentifier)enumeration.nextElement();
if(portId.getPortType() == 1)
{
System.out.println((new StringBuilder()).append("Port name:
").append(portId.getName()).toString());
SimpleRead simpleread;
if(portId.getName().equals("COM5"))
simpleread = new SimpleRead();
6.3 Port parameters (JAVA)
serialPort = (SerialPort)portId.open("SimpleReadApp", 1000);
inputStream = serialPort.getInputStream();
serialPort.setSerialPortParams(0xf4240, 8, 1, 0);
int i = 0;
6.4 Waiting for an (data stream) input from Arduino (JAVA)
do // infinite loop starts here
{
System.out.println("started the if else ");
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17. while(!isImageStart(inputStream, 0))
// image Generation code goes here
} while(true);
}
catch(Exception exception)
6.5 Image generation from received data stream (JAVA)
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18. Figure 14: Algorithm for image generation from received data steam
while(!isImageStart(inputStream, 0))
{
System.out.println("Looking for image");
System.out.println((new StringBuilder()).append("Found image:
").append(i).toString());
for(int j = 0; j < 240; j++)
{
for(int l = 0; l < 320; l++)
{
int j1 = read(inputStream);
ai[j][l] = (j1 & 0xff) << 16 | (j1 & 0xff) << 8 | j1 &0xff;
}
}
for(int k = 0; k < 240; k++)
{
for(int i1 = 0; i1 < 320; i1++)
ai1[i1][k] = ai[k][i1];
}
BMP bmp = new BMP();
bmp.saveBMP((newStringBuilder()).append("c:/out/").append(i+
+).append(".bmp").toString(), ai1); System.out.println((new
StringBuilder()).append("Saved image: ").append(i).toString());
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19. }
HANDLING MULTIPLE SCANS (CMD)
It is sometime needed to perform multiple scans. That means the scanning
mechanism is provided input for scan again and again, then this program as shown
in figure 15 proves to be useful it takes the user inputs to perform a certain number
of scans and then control the Arduino or any other microcontroller to perform the
scanning and PDF conversion till it reaches the provided number of scans.
Figure 15: Algorithm to handle multiple Scans
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20. IMAGE TO PDF CONVERSION (CMD)
Now after generating the images we need to convert those images to a PDF file for
which we will use the software ConvertITP.EXE. following is the algorithm for
Image to PDF conversion.
Figure 16: Algorithm Image to PDF generation
8.1 Code for the Image to PDF conversion
@echo off
echo by somnath
echo .
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21. set CITP="%ProgramFiles%Softinterface, IncConvert Image To
PDFConvertITP.EXE"
set InputFolder=C:out
set OutputFolder=C:out
REM Convert from JPG to PDF
%CITP% /S%InputFolder%*.bmp /T%OutputFolder%all_img.PDF /F0 /+
ren %InputFolder%all_img.PDF all_img-%date:~10,4%%date:~7,2%
%date:~4,2%_%time:~0,2%%time:~3,2%.pdf
mkdir %InputFolder%original_images_%date:~10,4%%date:~7,2%
%date:~4,2%_%time:~0,2%%time:~3,2%
move /Y %InputFolder%*.bmp %InputFolder%original_images_%date:~10,4%
%date:~7,2%%date:~4,2%_%time:~0,2%%time:~3,2%
echo `
echo DONE!
echo .
exit
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22. SOFTWARE SETUP GUIDE
-Extract the Extra.zip file. Then copy:
"win32com.dll" to "..jdk1.8.0_74jrebin” Directory.
the "comm.jar" in "...jdk1.8.0_74jrelibext"
"javax.comm.properties" in "...jdk1.8.0_74jrelib"
Copy “out” folder to C: Drive
Install the software “Installme.exe”
Double click on SCAN.bat from c:out folder
It will start the program
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23. CONCLUSION
Interfaced the OV7670 Camera module with Arduino at 8 MHz XCLK pulse
which is generated by the Arduino board itself. Arduino talk to the camera module
using I2C to write/read camera registers. Frames are read one by one in a brute-
force manner. Currently the camera module is configured to work with QCIF
(176x144) format in order to eliminate timing issues. Pixels of a given frame are
stored in the java program and on completion of whole row data the JAVA
program generates the valid BMP image.
The most challenging task for interfacing Arduino &Camera is the low
memory capacity of Arduino microcontroller due to which we are unable to store a
full image at once, to overcome this the JAVA program is implemented that
receive the Data Bits of one row at a time.
It has also to be noted that there are microcontrollers out there that
actually have dedicated peripherals/devices for interfacing with camera modules
such as the OV7670, but the interface of OV7670 Camera Module with Arduino
Microcontroller provides us a easy to use, maintain, low cost and a configurable
system that can be used in various fields of image acquisition.
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24. References
[1] N. Sriskanthan and Tan Karand. “Bluetooth Based Home Automation System”.
Journal of Microprocessors and Microsystems, Vol. 26, pp.281-289, 2002.
[2] Al-Ali, Member, IEEE & M. AL-Rousan,“Java-Based Home Automation System R.”
IEEE Transactions on Consumer Electronics, Vol. 50, No. 2, MAY 2004
[3] The Java Tutorials: All About Sockets [Online]. Available:
http://docs.oracle.com/javase/tutorial/networking/sockets, March
2013
[4] L. Lo Presti, M. La Cascia, “Real-Time Object Detection in Embedded Video
Surveillance Systems,” Ninth International Workshop on Image Analysis for Multimedia
Interactive Services, 7-9 May 2008, pp. 151-154.
[5] http://arduino.cc/en/Main/ArduinoBoardADK
[6] https://forum.arduino.cc/index.php?topic=211741.0
[7] http://www.dejazzer.com/coen4720/labs/lab11_camera.pdf
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