Hi, I'm using an ADV7842 to convert an analog video input into digital output. The analog signal is a test pattern from an Extron VTG 400. When going from the VTG 400 to the VGA input of a monitor, the test pattern is properly displayed as shown immediately below:
When going from the VTG 400 to the ADV7842 and then out of the ADV7842 to the DVI input of the same monitor the output looks like this:
I'm trying to fix this by adjusting DE H/V start/end and HSync start/end by adjusting the following CP registers of the ADV7842:
- DE_H_START: Address 0x8B [3:2]; Address 0x8D [7:0]
- DE_H_END: Address 0x8B [1:0]; Address 0x8C [7:0]
- DE_V_START Address 0x8E [7:4]
- DE_V_END Address 0x8E [3:0]
- START_HS: Address 0x7C[3:2]; Address 0x7E[7:0]
- END_HS: Address 0x7C[1:0]; Address 0x7D[7:0]
I have the ADV7842 DE, HSync and VSync output signals hooked up to a scope.
When I adjust DE_H_END, I see the falling edge of the DE signal change as shown below, however, when I adjust DE_H_START, there is no change in the DE signal. Here is a picture to explain:
Similarly, when I adjust END_HS, the falling edge of the HSYNC square wave will change position, causing the width of the square wave to increase/decrease but changing the START_HS value has no effect.
I've double checked the firmware and it is indeed changing the values of the DE_H_START and START_HS. I confirmed by reading back the values of the registers after writing to them.
Any suggestions as to why modifying these registers is having no effect on the output would be greatly appreciated. Thank you.
