No color on some programs (when there should be) ???

RobotWorkshop

I've tried my hand wired Hydra system on a couple different TV's with the composite input with slightly different results. Overall the system works fine running the games that came pre-loaded on an SD MAX cartridge. However, some of the games and demos which should be in color just show up in black/white on the screen. One in particular "Alien Invaders" shows up in color on one set and black/white on the other.

Has anyone run into this before? If so what may cause this?

I've been searching online for possible solutions and one mentioned that the clock speed may be off slightly. Since I didn't have a new 10Mhz crystal on hand I had used one that had been in my spare parts drawer. If the crystal was a bit off would that affect the color?

From the board to the connector is a short jumper (unshielded) with a 2-pin header to connect to the board. I wonder if this may be part of the problem. If so I have some small lengths of RG-174 coax I can use to replace that jumper.

At the moment I have a few things to try:

- Try to connect the Hydra to the VCR instead of directly to the input on the TV
- Try connecting it to a regular color composite monitor
- Swap out the short jumper cable from the board to the the connector
- Swap out the 10Mhz crystal

Any other suggestions?

tpw_man

Crystal speed definitely can affect color. The reason is because there are color pulses at specific times in the signal to display color. If the crystal is off, those don't arrive at the right time for the TV set to pick up the color. I don't know about any of the other things though.

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Spork Frog

It really depends on two things:

1. The actual crystal frequency. The drivers normally use a frequency divider/PLL loop based on the crystal, and not everything divides evenly into 10 million.
2. The video driver -- some push it a little, like HEL's slightly longer HSYNC cycle.

The signal outputted by the Hydra is not exactly a 100% in-spec signal at all times, due partially to crystals and partially due to coding practices. Both of these affect the output, and depending on how picky your screen is (I've heard that PAL-based TV's are sometimes especially bad with not-quite-perfect NTSC signals as well as LCD screens.)

stevenmess2004

Are your TVs PAL or NTSC? If they only do PAL than you will need to change a setting to get the prop to output PAL.

RobotWorkshop

I suppose that would be an important point! Sorry for leaving that off. The TV's are both NTSC. One is a Toshibia CRT and the other is an older (12+ year) SONY projection TV. The SONY is displaying everything in black and white while the Toshiba will display some of the games in color (but not all). Before I re-wired the board from a demo board to the Hydra it would display the Propeller demo in color on the SONY. To do the Hydra conversion I had to change the crystal (from 5Mhz to 10Mhz) and move the connections for the composite output to the appropriate pins. So perhaps it may be that the crystal I installed is a bit off or may be the wrong style. Since it wasn't a crystal I ordered new I don't know if it has a series load capacitance or has a rating like 20pf, etc. I've read that if the wrong style is used it may still work but the frequency may be off slightly. If this is the case then perhaps that is what i'm seeing here. It may be close enough to display the picture and operate but off just enough to clobber the color information for some TV's.

Any thoughts?

JT Cook

I know for my Hydra board (which was a prototype) it has a different crystal then the ones that shipped. For all my stuff, I had to add 5000 to the clock setting to get color to work. Since your setup will get color on one TV and not the other, you might want to add 2000 or so (and just keep adjusting in 1000 or 500 increments).



Anyway here is what I have to put in my programs to get color

_xinfreq = 10_000_000 + 5000

RobotWorkshop

So that is why i've seen that +(some number) after the clock speed! I can definitely try adding that to see if that fixes the problem. If that does correct the color then I suppose it would suggest my crystal is off.

If that is the case the I can try swapping out the crystal with a couple different styles to see if I can get it working with the standard setting. I'd rather do that and get the board working exactly as it should instead of having to tweak and recompile code to get it working perfect on my board. Swapping it isn't a problem since it's just two pins to unsolder! The crystals are fairly cheap and I'm going to order some the next time I need some parts.

Have you thought about swapping your crystal to see if you can drop that extra setting on your board?

Robert

JT Cook

It doesn't bother me enough to do it. The thing is once you find the "tweak" value, it is the same for all the programs. So all I have to do to fix it is just add + 5000 , I don't have to guess for every program.

Also once you find the right tweak number, then it should work on all TVs. I have tested my racing·game on 2 CRT TVs, 1 Digital DLP TV, and a PC with a video capture card and they were all in color.

Post Edited (JT Cook) : 4/15/2008 10:54:08 PM GMT

RobotWorkshop

True. I was just thinking that it might help for programs where the source hasn't been published and there is only a binary image of the program available. I'll try tweaking that setting and once the new crystals come in i'll post what I find out.

Robert