THS8200: How to generate test colorbar for resolution 640x480

Larry,

Thank you very much, I have got test output now.

Hi Larry,

I  followed your settings, but i can't got the color bars output to my computer monitor. My platform is based on 6446EVM,  and using the EVM's lsp. Now I doubt whether the  VPBE had wrong settings(e.g. VENC) . Can you give some adives?

Thanks in advance! 

Berline,

You reported ealier that you were able to display the VGA60Hz test bars using a 27MHz clock.  Are you using the same setup with 6446EVM?  Have you confirmed that the EVM is ouputting the same 27MHz clock?  If a differnet clock frequncy is being used, the THS8200 settings need to be adjusted to compensate for clock frequency change.

Larry:

 I got it ! Thanks a lot.

Hi Larry,

I had got another problem. My colorbar can't display in PC monitor or projector, but it can display in other monitor which integrated PC mode、HDMI and video mode. The colorbar can display in the PC mode in this monitor.I'm sure the Vsync and Hsync is right. You said 'VGA60Hz has negative sync polarities, so it cannot be supported.',what does it mean? My board just used one THS8200 without THS7303 and CDCE949, i don't what goes wrong. Can you give me some advices? 

 Any help would be appreciated.

Berlin Chen 

Design Engineer --China

Berlin,

Correct, the THS8200 has issues with negative output  sync polarities, when using internal color bar generation.   Can you set up for an SVGA fomat which uses positive sync polarities?  If you need to support only VGA with negative syncs, you can set up for postive syncs and then use invertors.

Always check the THS8200 output syncs with a scope for correct timing.  Some monitors may not be compatible with 3.3V syncs.  3.3V/5V level translators are recommended on the output syncs to drive the monitor.

Hi Larry,

I have another question.There is a QT application, could i display it on my monitor via VGA .

Berlin,

We will need more detail on the QT applcation to answer this.

hi Larry,

     I got it.My UI and video could display on my monitor via VGA.But there is another problem.My Hsync and Vsync amplitude just about 1.8V.Some PC monitor can't get the H/Vsync signals. I think there was something wrong with my circuits.In ths8200 document i found there were three pins named VDD_IO(NO. 19, 46, 70),and was described that 'I/O ring power, 1.8 V or 3.3 V nominal'.In my board,VDD_IO pins connected 1.8V.I think these pins can effect H/Vsync signals output. If i want H/Vsync pins output 3.3V signals should i have give VDD_IO pins 3.3V.   Any help would be appreciated.

Berlin Tron

2011.08.18

Berlin,

Yes, HSOUT and VSOUT levels, I2C levels, and RGB level are all deterrmined from VDD_IO.   We actually recommend using level translators on the output syncs when 3.3V VDD_IO is used, since VGA syncs are typcially 5V.

What RGB data input levels are you using?  Note that 1.8V I/O is not recommended when discrete HSIN and VSIN inputs are used with the THS8200, due to potential setup/hold time issues on the sync inputs.

Larry

Larry,

On this thread you suggested a workaround for generating color bars from the THS8200 in VESA 640x480 60Hz mode.  This relates to the negative syncs.  You suggested using inverters on the syncs.  

I have confirmed my VESA 640x480 60Hz output indeed has negative syncs.  My existing board doesn't have inverters.  Is there perhaps a way around this?  I need to operate in both regular mode and color bar mode.  Is the only way to reconfigure to positive syncs and then have something like a nor gate to reconfigure back to negative?  This would require a board mod, of course.  I'm looking for an easier way.  (I don't even know if such positive sync configuring is possible.  Maybe by mucking with the timing to move the syncs totally around so off is on and on is off.)

Alternatively, what I'm really looking for is "proof-of-life" during my slow boot up.  My prior ADV7171 NTSC output device used the ADV7171 internal color bars.  This THS8200 VESA 640x480 60Hz device does not HAVE to use color bars.  It could use anything else.  I just don't have a digital video signal coming in from the processor yet.  One thing I've thought of is to hard code a single frame in the driver, and sent it out as soon as the driver is [what? "probed", "opened", something early].  Are there any other ways.

Thanks,

Helmut

P.S. You were helping me with a ghost in December.  My ghost went away with the next working board of the same rev, a board WITHOUT all the resistors jumpered onto it.  This must have been a 'going around the block' kind of problem.  Once I had good software, I didn't need the resistor jumpers.  It must have been the resistors causing the ghost.  Note also I used the white balance multiplier to get my voltage levels correct.  Maybe it was for voltage levels that I was messing with the resistor jumpers.  Anyway, that's done with...

Helmut,

Do you have to use a VGA format  during boot-up?   One work-around would be to use an SVGA or XGA format with positve syncs, but base line rate and frame rate timing on a VGA clock frequency.  The HSync width may not be precisely correct, but should be close enough.

Glad to hear the other problem is resolved.

Regards,

Larry

...great minds think alike...  or is that too egotistical?