I have built a uzebox, with mega644P and AD725, using the schematic of "Uzebox-rev-C1.pdf"
already can control led through joypad, means mega644P work normally.
but when output signal to a Hisense intelligent TV's AV interface, no display. I'll check the AD725 circuit again.
Does AV signal distinguish between NTSC and PAL?
if it does, How do I modifiy the code to adapt PAL? where are the key points in code. thanks so much.
Does AV signal distinguish between NTSC and PAL?
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springvirus
- Posts: 15
- Joined: Thu May 14, 2015 5:20 am
Re: Does AV signal distinguish between NTSC and PAL?
You can't modify the kernel for PAL because not only would it be a big rewrite, but it requires more bandwidth and will not be compatible with any games. Try to test it on other tvs since pretty much all ones since the 90s supports pal and ntsc natively. Do you have an oscilloscope?
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CunningFellow
- Posts: 1486
- Joined: Mon Feb 11, 2013 8:08 am
- Location: Brisbane, Australia
Re: Does AV signal distinguish between NTSC and PAL?
It is worse than it being a re-write. A re-write would be possible though maybe hard.
It's actually a change of clock frequency and THAT is impossible.
The Uzebox runs at 28.63 Mhz. That is not just a random number, but is in fact the NTSC colour carrier frequency x8. It needs to be this x8 to be able to drive the AD725s x4 clock input (saving crystals/chips) and also make the pixel clock a factor of the colour carrier (which avoids the worst of dot crawl)
The PAL colour carrier is 4.43Mhz so that would mean the AVR would have to run 35.5Mhz.
The AVR is already being overclocked to 28Mhz. 8mhz over its rated speed of 20Mhz. It gets by on this overclocking barely in the DIP package (some chips fail and some need "over volting"). Even in the DFN package with good decoupling the BEST I have seen an ATMega644 overclock too was ~33Mhz.
It's actually a change of clock frequency and THAT is impossible.
The Uzebox runs at 28.63 Mhz. That is not just a random number, but is in fact the NTSC colour carrier frequency x8. It needs to be this x8 to be able to drive the AD725s x4 clock input (saving crystals/chips) and also make the pixel clock a factor of the colour carrier (which avoids the worst of dot crawl)
The PAL colour carrier is 4.43Mhz so that would mean the AVR would have to run 35.5Mhz.
The AVR is already being overclocked to 28Mhz. 8mhz over its rated speed of 20Mhz. It gets by on this overclocking barely in the DIP package (some chips fail and some need "over volting"). Even in the DFN package with good decoupling the BEST I have seen an ATMega644 overclock too was ~33Mhz.
Re: Does AV signal distinguish between NTSC and PAL?
Yes, you are even more right. 
I had ansewered the same thing to many times and I forgot the essential. 
I'll put you answer in the WIKI's FAQ.
I had ansewered the same thing to many times and I forgot the essential. I'll put you answer in the WIKI's FAQ.-
springvirus
- Posts: 15
- Joined: Thu May 14, 2015 5:20 am
Re: Does AV signal distinguish between NTSC and PAL?
Yeah, I have an oscilloscopeuze6666 wrote:You can't modify the kernel for PAL because not only would it be a big rewrite, but it requires more bandwidth and will not be compatible with any games. Try to test it on other tvs since pretty much all ones since the 90s supports pal and ntsc natively. Do you have an oscilloscope?