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Old Jul 04, 2013, 10:51 AM
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Paraguay, Central, Lambare
Joined Mar 2013
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You use PAL or NTSC?


Quote:
Originally Posted by schugabe View Post
My new Flytron SimpleOSD X2 gives me a hard time to get it running. I posted my problems on the flytron forum but got no response here... I hope that someone here can give me some hints how to improve the performance of the osd.

My camera is the new fatshark cmos 600tvl camera. Summary of my problems:
  • With dim_on set to 1 no information of the osd is readable, it looks like the picture in post 2271
  • With dim_on set to 0 the image is still not very stable but readable, the problems start if there are some darker areas in the image. Then the lines start to move over the whole screen again. When the light situation changes everything is readable again.

I searched this thread for informations and learned that changing the resistor values between the two pins of the atmega and the video signal influence this behavior. Currently both resistors have a value of 100Ohm.

To better understand the problem I hooked the video signal to a scope. The problems are pretty obvious to spot. First a plot without the osd connected:



Note that the peak-to-peak voltage is ~0.7V. The sync signals for the new frame a done correctly (from what I can tell) and the LM1881 should have no troubles to recognize the frame/line starts. This situation changes with the osd connected:



The peak-to-peak voltage is now ~1.5V and the black signal is below the original sync signal level... it is not surprising that the LM1881 gets confused and starts generating spurious interrupts.

Do I have to increase or lower the resistor values to adjust the output of the osd to the camera? I don't have much experience in smd soldering so I don't want to try messing around without knowing that the result will probably be an improvement. Or do I have to do something completely different like capacitors somewhere?

I also did some improvements to the firmware of the SimpleOSD X2. It now supports digital rssi (PWM signals) from receivers like the ezuhf rx. After some short tests the results look quite good but more testing has to be done to make sure everything still works like it should. The source code is in my github repository: https://github.com/schugabe/DIY-OSD
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