Make Your Own Camera
Intro: Make Your Own Camera
This instructable explains how to make a monochrome camera using an Omnivision OV7670 image sensor, an Arduino microcontroller, a few jumper wires, and Processing 3 software.
Experimental software for obtaining a color image is also presented.
Press the “c” key to capture a 640*480 pixel image ... press the “s” key to save the image to file. Successive images are sequentially numbered should you wish to create a short time-lapse movie.
The camera is not fast (each scan takes 6.4 seconds) and is only suitable for use in fixed lighting.
The cost, excluding your Arduino and PC, is less than a cup of coffee.
Images
The component parts, without jumper wiring, are shown in the opening photo.
The second photo is a screen-shot showing the Arduino camera software and the Processing 3 frame-grabber. The inset shows how the camera is connected.
The video demonstrates the camera in action. When the “c” capture key is pressed there is a brief flash followed by a burst of activity as the image is scanned. The image automatically appears in the display window once the scan is complete. The images are then seen to appear in the Processing folder following each press of the “s” key. The video concludes by cycling rapidly through each of the three saved images.
STEP 1: Circuit Diagram
The circuit diagram, for all versions of this camera, is shown in photo 1.
Photos 2, 3 show how the jumpers-wires and components are connected.
Without the aluminium bracket the images are lying on their side.
Warning
Program your Arduino BEFORE attaching any jumper wires to the OV7670 camera chip. This will prevent 5 volt output pins from a previous program from destroying the 3v3 volt OV7670 camera chip.
STEP 2: Parts List
The following parts were obtained from https://www.aliexpress.com/
- 1 only OV7670 300KP VGA Camera Module for arduino DIY KIT
- 1 only camera bracket complete with nuts and bolts
- 1 only UNO R3 for arduino MEGA328P 100% original ATMEGA16U2 with USB Cable
The following parts were obtained locally
- 18 anly Arduino male-female jumper cables
- 3 only Arduinin female-female jumper cables
- 1 only mini bread-board
- 4 only 4K7 ohm 1/2 watt resistors
- 1 only scrap aluminium stand.
You will also need the following datasheets:
STEP 3: Theory
OV7670 camera chip
The default output from the OV7670 camera chip comprises a YUV (4:2:2) video signal and 3 timing waveforms. Other output formats are possible by programming the internal registers via an I2C compatible bus.
The YUV (4:2:2) video signal (photo 1) is a continuous sequence of monochrome (black & white) pixels separated by U (blue color difference) and V (red color difference) color information.
This output format is known as YUV (4:2:2) since each group of 4 bytes contains 2 monochrome bytes and and 2 color bytes.
Monochrome
To obtain a monochrome image we must sample every second data byte.
An Arduino only has 2K of random access memory but each frame comprises 640*2*480 = 307,200 data bytes. Unless we add a frame-grabber to the OV7670 all data must sent to the PC line-by-line for processing.
There are two possibilities:
For each of 480 successive frames, we can capture one line to the Arduino at high speed before sending it to the PC at 1Mbps. Such an approach would see the OV7670 working at full speed but would take a long time (well over a minute).
The approach that I have taken is to slow the PCLK down to 8uS and send each sample as it comes. This approach is significantly faster (6.4 seconds).
STEP 4: Design Notes
Compatibility
The OV7670 camera chip is a 3v3 volt device. The data sheet indicates that voltages above 3.5 volts will damage the chip.
To prevent your 5 volt Arduino from destroying the OV7670 camera chip:
- The external clock (XCLK) signal from the Arduino must be reduced to a safe level by means of a voltage divider.
- The internal Arduino I2C pull-up resistors to 5 volts must be disabled and replaced with external pull-up resistors to the 3v3 volt supply.
- Program your Arduino BEFORE attaching any jumper-wires as some of the pins may still be programmed as an output from an earlier project !!! (I learnt this the hard way ... fortunately I bought two as they were so cheap).
External clock
The OV7670 camera chip requires an external clock in the frequency range 10Mhz to 24MHz.
The highest frequency we can generate from a 16MHz Arduino is 8MHz but this seems to work.
Serial link
It takes at least 10 uS (microseconds) to send 1 data byte across a 1Mbps (million bits per second) serial link . This time is made up as follows:
- 8 data bits (8us)
- 1 start-bit (1uS)
- 1 stop-bit (1uS)
Internal clock
The internal pixel clock (PCLK) frequency within the OV7670 is set by bits[5:0] within register CLKRC (see photo 1). [1]
If we set bits[5:0] = B111111 = 63 and apply it to the above formula then:
- F(internal clock) = F (input clock)/(Bit[5:0}+1)
- = 8000000/(63+1)
- = 125000 Hz or
- = 8uS
Since we are only sampling every second data byte, a PCLK interval of 8uS results in a 16uS sample which is sufficient time to transmit 1 data byte (10uS) leaving 6uS for processing.
Frame rate
Each VGA video frame comprises 784*510 pixels (picture elements) of which 640*480 pixels are displayed. Since the YUV (4:2:2) output format has an average of 2 data bytes per pixel, each frame will take 784*2*510*8 uS = 6.4 seconds.
This camera is NOT fast !!!
Horizontal positioning
The image may be moved horizontally if we change the HSTART and HSTOP values while maintaining a 640 pixel difference.
When moving your image left, it is possible for your HSTOP value to be less than the HSTART value!
Don’t be alarmed ... it is all to do with counter overflows as explained in photo 2.
Registers
The OV7670 has 201 eight-bit registers for controlling things such as gain, white balance, and exposure.
One data byte only allows for 256 values in the range [0] to [255]. If we require more control then we must cascade several registers. Two bytes gives us 65536 possibilities ... three bytes give us 16,777,216.
The 16 bit AEC (Automatic Exposure Control) register shown in photo 3 is such an example and is created by combining portions of the following three registers.
- AECHH[5:0] = AEC[15:10]
- AECH[7:2 ] = AEC[9:2]
- COM1[1:0] = AEC[1:0]
Be warned ... the register addresses are not grouped together !
Side effects
A slow frame rate introduces a number of unwanted side effects:
For correct exposure, the OV7670 expects to work at a frame rate of 30 fps (frames per second). Since each frame is taking 6.4 seconds the electronic shutter is open 180 times longer than normal which means all images will be over-exposed unless we alter some register values.
To prevent over-exposure I have set all of the AEC (auto exposure control) register bits to zero. Even so a neutral density filter is needed in front of the lens when the lighting is bright.
A long exposure also appears to affect the UV data. As I have yet to find register combinations that produce correct colours ... consider this to be work in progress.
Note
[1]
The formula shown in the data sheet (photo 1) is correct but the range only shows bits[4:0] ?
STEP 5: Timing Waveforms
The note in the bottom left corner of the “VGA Frame Timing” diagram (photo 1) reads:
For YUV/RGB, tp = 2 x TPCLK
Figures 1, 2, & 3 verify the data sheet(s) and confirm that Omnivision treats every 2 data bytes as being the equivalent of 1 pixel.
The oscilloscope waveforms also verify that HREF remains LOW during the blanking intervals.
Fig.4 confirms that the XCLK output from the Arduino is 8MHz. The reason we see a sinewave, rather than a squarewave, is that all of the odd harmonics are invisible to my 20MHz sampling oscilloscope.
STEP 6: Frame Grabber
The image sensor within an OV7670 camera chip comprises an array of 656*486 pixels of which a grid of 640*480 pixels are used for the photo.
The HSTART, HSTOP, HREF, and VSTRT, VSTOP, VREF register values are used to position the image over the sensor. If the image is not positioned correctly over the sensor you will see a black band over one or more edges as explained in the “Design Notes” section.
The OV7670 scans each line of the picture one pixel at a time starting from the top left corner until it reaches the bottom right pixel. The Arduino simply passes these pixels to the PC via the serial link as shown in photo 1.
The frame-grabbers’ task is to capture each of these 640*480=307200 pixels and display the contents in an “image” window
Processing 3 achieves this using the following four lines of code !!
Code line 1:
- byte[] byteBuffer = new byte[maxBytes+1]; // where maxBytes=307200
The underlying code in this statement creates:
- a 307201 byte array called “byteBuffer[307201]”
- The extra byte is for a termination (linefeed) character.
Code line 2:
- size(640,480);
The underlying code in this statement creates:
- a variable called “width=640;”
- a variable called “height=480”;
- a 307200 pixel array called “pixels[307200]”
- a 640*480 pixel “image” window in which the contents of pixels[] array are displayed. This “image” window is continuously refreshed at a frame rate of 60 fps.
Code line 3:
- byteCount = myPort.readBytesUntil(lf, byteBuffer);
The underlying code in this statement:
- buffers the incoming data locally until it sees a “lf” (linefeed) character.
- after which it dumps the first 307200 bytes of local data into the byteBuffer[] array.
- It also saves the number of bytes received (307201) into a variable called “byteCount”.
Code line 4:
- pixels[i] = color(byteBuffer[i]);
When placed in a for-next-loop, the underlying code in this statement:
- copies the contents of the “byteBuffer[]” array to the “pixels[]” array
- the contents of which appear in the image window.
Key Strokes:
The frame-grabber recognises the following keystrokes:
- ‘c’ = capture the image
- ‘s’ = save the image to file.
STEP 7: Software
Download and install each of the following software packages if not already installed:
- “Arduino” from https://www.arduino.cc/en/main/software
- “Java 8” from https://java.com/en/download/ [1]
- "Processing 3” from https://processing.org/download/
Installing the Arduino sketch:
- Remove all OV7670 jumper wires [2]
- Connect a USB cable to your Arduino
- Copy the contents of “OV7670_camera_mono_V2.ino“ (attached) into an Arduino “sketch” and save.
- Upload the sketch to your Arduino.
- Unplug the Arduino
- You can now safely reconnect the OV7670 jumper wires
- Reconnect the USB cable.
Installing and running the Processing sketch:
- Copy the contents of “OV7670_camera_mono_V2.pde” (attached) into a Processing “sketch” and save.
- Click the top-left “run” button ... a black image window will appear
- Click the “black” image-window
- Press the “c” key to capture an image. (approx 6.4 seconds).
- Press the “s” key to save the image in your processing folder
- Repeat steps 4 & 5
- Click the “stop” button to exit the program.
Notes
[1]
Processing 3 requires Java 8
[2]
This is a “once only” safety step to avoid damaging your OV7670 camera chip.
Until the sketch “OV7670_camera_mono.ini” has been uploaded to your Arduino the internal pull-up resistors are connected to 5 volts, plus there is the possiblity that some of the Arduino data lines may be 5 volt outputs ... all of which are fatal to the 3v3 volt OV7670 camera chip.
Once the Arduino has been programmed there is no need to repeat this step and the register values may be safely changed.
STEP 8: Obtaining a Color Image
The following software is purely experimental and is posted in the hope that some of the techniques will prove useful. The colors appear to be inverted ... I have yet to find the correct register settings. If you find a solution please post your results.
If we are to obtain a color image, all data bytes must be captured and the following formulas applied.
The OV7670 uses the following formulas to convert RGB (red, green, blue) color information into YUV (4:2:2): [1]
- Y = 0.31*R + 0.59*G + 0.11*B
- U = B – Y
- V = R – Y
- Cb = 0.563*(B-Y)
- Cr = 0.713*(R-Y)
The following formulas may be used to convert YUV (4:2:2) back to RGB color: [2]
- R = Y + 1.402* (Cr – 128)
- G = Y – 0.344136*(Cb -128) – 0.714136*(Cr -128)
- B = Y + 1.772*(Cb -128)
The attached software is simply an extension of the monochrome software:
- A “c” capture request is sent to the Arduino
- The Arduino sends the even numbered (monochrome) bytes to the PC
- The PC saves these bytes into an array
- The Arduino next sends the odd numbered (chroma) bytes to the PC.
- These bytes are saved into a second array ... we now have the entire image.
- The above formulas are now applied to each group of four UYVY data bytes.
- The resulting color pixels are then placed in the “pixels[]” array
- The PC scans the “pixels[]” array and an image appears in the “image” window.
The Processing 3 software briefly displays each scan and the final results:
- Photo 1 shows the U & V chroma data from scan 1
- Photo 2 shows the Y1 & Y2 luminance data from scan 2
- Photo 3 shows the color image ... only one thing is wrong ... the bag should be green !!
I will post new code once I have solved this program ...
References:
[1]
http://www.haoyuelectronics.com/Attachment/OV7670%... (page 33)
[2]
https://en.wikipedia.org/wiki/YCbCr (JPEG conversion)
Click here to view my other instructables.
60 Comments
mcjinkz 3 years ago
lingib 3 years ago
Much as I would like to help I do not have the necessary parts, or time, to devote to your project.
The following links to similar projects may be of help:
https://www.robotshop.com/community/forum/t/c328r-...
https://sean.voisen.org/projects/pigeonblog/
https://github.com/svoisen/c328r
naren1603 3 years ago
lingib 3 years ago
I have since dismantled this project so am unable to replicate your conditions but the following guidelines should help pinpoint the problem:
Step 1:
-------
- Check your wiring
Step 2:
-------
Then confirm that your Processing software is working.
To do this change your arduino code to match the high-lighted text in in each of the attached Serial_write_0x00.jpg , Serial_write_0x80.jpg, and Serial_write_0xD0.jpg screen-shots:
- 0x00 produces a black screen as shown in Serial_write_0x00.jpg.
- 0x80 produces a mid-gray screen as shown in Serial_write_0x80.jpg.
- 0xD0 produces a light-gray screen as shown in Serial_write_0xD0.jpg
- 0xFF will produce a completely white screen.
Step 3:
-------
Now view the actual data being sent on your Arduino "Serial monitor" ... it appears that you are sending a string of zeros (which equates to black).
This will happen if:
- your lens-cap is still on or
- your gain setting is too low for your camera module.
Step 4
--------
The gain setting can be checked by writing a '1' into each of the bit positions shown in shown in Gain_high.jpg (attached).
With a '1' written into every bit position your Processing screen should go white (your Serial Monitor will also show a string of 'F's which equates to white)
With a '0' written into every bit position you should get an image as shown in Gain_zero.jpg (attached).
I found that with a gain setting of 4 (binary 00000000 00000001 00) the image started to over-expose as shown in Gain_four.jpg (attached).
Other possibilities:
--------------------
My observation is that the pictures tended to over-expose when the light was bright ... but your screen is black which points to:
- Possible instability due to wiring layout
- Faulty OV7670 module
naren1603 3 years ago
lingib 3 years ago
WarayutSitha 5 years ago
So my camera have no FIFO it's can sent with baudrate 9600 ?
If i want to use your code or rewrite the new code Arduino and Processing can you advice the way or position i have to change?
**Now you are only one teacher can ask and help me my project have to sent next 2 week
**Pls help me and Thank you for all your assistance. :)
lingib 5 years ago
If you Google "camera arduino 9600 bauds", or similar, you may find a project that matches your requirement for a 9600 baud link.
One such search result is "https://www.robotshop.com/community/forum/t/c328r-camera-and-arduino/2853" in which the blog states:
"I've used Sean Voisen's C++ code [1] as a base and inspiration for most of my Arduino code. His example shows you how to use his Arduino library to take snapshots with the camera, store them to an EEPROM, and then send the data through a serial port to a Processing sketch that displays the picture - turning the Arduino into a camera."
It would appear that a solution to your problem is to store the image to an EEPROM locally before sending it at 9600 bauds.
Good luck with your project ...
[1]
https://sean.voisen.org/projects/pigeonblog/
https://github.com/svoisen/c328r
WarayutSitha 5 years ago
I will try the way that you recommend and i will to update foe you It's work or not.
Thank you so much :) have a good day
WarayutSitha 5 years ago
I have a small project. and I have to use this OV7670.
I'm done follow your all step and I have changed BuadRate from 1M to 9600. with Arduino and Processing code.
when I open and run code in Processing. It's have no anything to show.
when i press C have no value to show in serial monitor and when i press S have photo screen save in my folder.
Thank for help.
lingib 5 years ago
The default baud speed for this project is 1000000. The project will NOT work if you set the baud speed to 9600.
The processing code appears to be working as you appear to have captured the blank screen shown in your first image.
Please read my responses to previous questions in the comments section as they contain all the debug information that you need.
WarayutSitha 5 years ago
What does it's mean ?
WarayutSitha 5 years ago
lingib 5 years ago
Try the 'A' and 'Z' test code ....
WarayutSitha 5 years ago
I have cleared with all problem. my picture is OK.
but for my Project i have to sent It's must use buadrate 9600
Can you advice the way to do that for me?
***I appreciate your help :)***
lingib 5 years ago
You would need a camera module with an on-board buffer (frame-grabber) to send an image at 9600 bauds. You would also need a different circuit and different code.
The on-board buffer would "instantly" capture the image data which can then be extracted and sent at 9600 bauds ... but it will take a long time.
If it takes 6.4 seconds to send an image at 1000000 bauds then it will take approximately 10 minutes to send the same amount of information at 9600 bauds.
WarayutSitha 5 years ago
lingib 5 years ago
To get around this the test code uses the value 128 (which is half way between 0 and 255) as a reference point. If the OV7670 data value is less than 128 it prints the letter 'A' (which is visible) ... If the OV7670 data value is greater than 128 it prints the letter 'Z'.
Your OV7670 appears to be working as you are getting the letters 'A' and 'Z' when you block the light with your hand.
You will NOT get an image if you send the 'A' 'Z' test data to the frame-grabber.
The frame-grabber and "Serial Monitor" cannot be used at the same time.
WarayutSitha 5 years ago
***And now im going to make sure that my wire is right and serial port is right too.
for me i assume that a big problem from wire. Thank you
lingib 5 years ago
You should see the the number 307201 after this list once the camera has finished sending its data.
The number 307201 is the number of data bytes received by the frame-grabber comprising 640*480=307200 data bytes + 1 line-feed character.
You may be connected to the wrong serial port as nothing is shown after the list of serial ports ?