Hacking a backup camera: Remove OSD

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Hacking a backup camera: Remove OSD

Unread postby Derrick » Sat Nov 16, 2013 4:32 pm

So I got this wide angle 170deg backup camera from Amazon for like $14. Not a bad deal.
http://www.amazon.com/gp/product/B005CT ... m-feens-20
61ZDQhLlL7L__SL1000_.jpg
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Trouble is that someone was really passionate about helping me use this to back up my car. There is a somewhat presumptuous on screen display with some grid lines to guide me into my parking spot, nice for that I guess but pretty distracting for any other purpose.
WP_20131115_002.jpg
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The camera had a large coupler inline with the cord where the single cable from the camera was broken out into two wires for power in and video out.
coupler.PNG
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I was hopeful that the OSD (on screen display) might be generated there, but not quite ready to cut cables, I opened up the camera.
WP_20131115_003.jpg
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I used a pin on the yellow wire to see if the video signal within the camera still has the OSD on it, which it did, so it's not generated in the coupler.
Probing around on other wires visible in the first layer of circuitry did not reveal an unmodified video signal either.

This is the datasheet for the chip that it on top, it's a serial EEProm (memory).
http://pdf.datasheetcatalog.com/datashe ... oc0180.pdf
chip.PNG
eeprom
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So this is an i2c chip. i2c has weak pullups on the data (SDA) and clock (SCL) lines, and it's ok to ground the lines. My theory is that the eeprom chip contains a bitmap of the displayed OSD image.

Grounding the SDA line (pin 5) on the chip removed the OSD, theoretically this makes all the memory values look like zeros.
WP_20131116_005.jpg
video without OSD
WP_20131116_005.jpg (79.83 KiB) Viewed 39186 times


Connecting pins 4 and 5 on the eeprom chip, GND to SDA, effects a permanent fix.
Attachments
WP_20131116_004.jpg
fixored
WP_20131116_004.jpg (92.43 KiB) Viewed 39186 times
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Re: Hacking a backup camera: Remove OSD

Unread postby Derrick » Sat Nov 16, 2013 4:50 pm

My theory about it just being a bitmap seems to be at least partially incorrect though, as you may notice the screen image which is reversed in the first image as if you are looking in a rear view mirror, is not reversed in the second image.

There must be a bit variable in there for reversing the image. It's fortunate for my purpose that a zero causes it not to be reversed. (Theoretically)
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Re: Hacking a backup camera: Remove OSD

Unread postby Derrick » Sat Nov 16, 2013 5:45 pm

Did another one.
WP_20131116_006.jpg
cam
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Available here: http://www.amazon.com/gp/product/B009NV ... m-feens-20

WP_20131116_007.jpg
osd
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The chip was different, but in the hacking spirit I just tried the same method as I used on the first which worked.
I measured the current of the pin to ground to make sure that I wasn't shorting out anything too much, and it was 0.2mA, so good enough.
WP_20131116_008.jpg
inside
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WP_20131116_013.jpg
fixed
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WP_20131116_014.jpg
no OSD
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A little solder paste on the wire makes it easier to attach these wires. Just dip the wire in solder paste (sparingly), press to juction and touch with very hot iron.

This time the hack didn't resolve the reversed image, but good enough for me; I may actually use this one for a backup camera.
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Re: Hacking a backup camera: Remove OSD

Unread postby Michal » Mon Nov 18, 2013 2:29 pm

Nice,
when you ground SDA on I2C line, you won't get zeroes, rather you render the line unusable. I wonder what's in the EEPROM, maybe you can change the OSD image :)
https://www.youtube.com/watch?v=8ZYMrcHm91s

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Re: Hacking a backup camera: Remove OSD

Unread postby Derrick » Tue Nov 19, 2013 1:52 pm

Ahh yes, thanks for that observation.
It would be very cool to replace the image. May get another camera to play with.
Nice vid, but I don't see myself bit-banging the data out manually :P
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Re: Hacking a backup camera: Remove OSD

Unread postby Ron Swanson » Sun Mar 09, 2014 3:51 pm

Do you know how to reverse the image? I have two of these, one mounted on my front bumper and I would like to have the image appear correctly.

Thanks!

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Re: Hacking a backup camera: Remove OSD

Unread postby Derrick » Sun Mar 16, 2014 4:14 pm

Ron Swanson wrote:Do you know how to reverse the image? I have two of these, one mounted on my front bumper and I would like to have the image appear correctly.

Thanks!

The imaged reversal was corrected for the first camera in this thread, but not for the second.
Which is the camera that you have? Is it identical to the second camera?
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Re: Hacking a backup camera: Remove OSD

Unread postby Ron Swanson » Sun Mar 16, 2014 5:51 pm

I have the first camera although my board looks slightly different. Are you saying that by soldering the two pins together it reverses the image and removes the osd?

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Re: Hacking a backup camera: Remove OSD

Unread postby Derrick » Sun Mar 16, 2014 6:27 pm

Yes, for that first camera, hooking those two pins together removed the overlay and corrected the flipped image.

If the board is a little different, can you please post a picture?
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Re: Hacking a backup camera: Remove OSD

Unread postby Derrick » Sat Mar 29, 2014 1:01 am

I did another camera similar on the outside to the second camera above, but inside the board was completely different.

The chip was a 24C08C: 2-WIRE SERIAL E2PROM

Here's the board before modification:
WP_20140328_003.jpg
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I lifted the VCC pin, and that disabled both the overlay and the image reversal:
WP_20140328_006.jpg
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Closeup of the pin I lifted:
Lifted.PNG
Lifted.PNG (243.7 KiB) Viewed 38274 times
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