i want adv7180 ouput BB Black Burst,when adv7180 lock is lost.how to set the registers?i set 0X0C to 0x02 and 0X0D to 0x00 just now,but the output image was not pure black,it`s slant white.
If you want to output a black screen instead of a blue screen while free running try the following.
Set bits [1:0] of 0x0C to 10 (binary). This will enable free run mode when the ADV7180 loses lock.
Next you need to program the colour that will be displayed. The ADV7180 uses the YCbCr colour space.
There are equations freely available on the internet that describe the relationship between RGB and YCbCr.
Assuming the data has a range of 0-255 where 16-235 are valid levels.
Y = (0.257 * R) + (0.504 * G) + (0.098 * B) + 16
Cr = V = (0.439 * R) - (0.368 * G) - (0.071 * B) + 128
Cb = U = -(0.148 * R) - (0.291 * G) + (0.439 * B) + 128
(There are other equations out there so use which one you application needs)
So if you want black then find out its value in RGB.
Black in RGB is: R = 0 G = 0 B= 0.
Putting these values into the equations gives you
Y = 16 (means the lowest luma level allowed)
Cr = 128 (slightly above the midpoint of Cr)
Cb = 128 (slightly above the midpoint of Cb)
Convert these values for register 0x0D.
Y is in register 0x0C[7:2]. Lowest luma level should be 0.
Cr is in the register 0x0D[7:4]. Slightly above the midpoint is 0x8.
Cb is in the register 0x0D[3:0]. Slightly above the midpointis 0x8.
Putting this altogether gives you the following two writes:
0x42 0x0C 0x02
0x42 0x0D 0x88
I have tried this on the bench and I get a flat black screen output when free running.
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