Cycles used in the Uzebox

[neslou]

Hi all,
Any idea of how many cycles are used by the Kernel to produce 14,xxx Mhz that is feed to the AD725?
Actually, I would like to know if I use a 74f161 IC with a SD04 Dip swithes, I could use the Master Clock 28,xxxMhz and a divided by 8 synchronous signal for feeding a CXA1645PM RGB encoder? And also liberate one port from the Atmega644?
Maybe i am wrong, i am just searching for solution
I have seen that the kernel is using a 16Bit Counter etc.. in the general documentation.
Many thanks in advance for any reply.

Regards.

Neslou.

[D3thAdd3r]

In my opinion, adding another chip is not worth it. Only specific games that were no longer Uzebox compatible would be able to take advantage of it anyway, and I don't think in the end it would be a large number. If I understand things right, you only get back an extra timer, it seems the clock halving is effectively free besides costing just a timer that would otherwise be idle:

However the PB3/AD725 clocking incurs no overhead to the execution speed as this pin automatically toggles when a hardware timer attains a target value (in this case "1", or each other clock). So no need for interrupts here, and it's the beauty of AVR devices! That said, *some* cycles could have been saved if the CSYNC pin used the 16 bit timer OCx pin instead of interrupts. But I didn't saw that when doing the original design and after the AVCore & Fuzebox where out, it was too late...

Unless there is some fundamental advantage of using that encoder I can't see. You could of course recompile all games to be compatible with this system for whatever advantage you found in this direction, but direct binary compatibility with Uzebox seems a large benefit to a console such as this.

[neslou]

Thanks for your reply.
I think of two advantage.. the first one, DIP package for the video encoder CXA1645, the second one is that it is cheaper and also i can use Scart / Svideo connector if i don't make mistake?

[D3thAdd3r]

On the software side, I think you could recompile games to use a timer value of 7 instead of 1 to use CXA1645 without more ICs, but I don't think that is the solution you want.

I do not know what the cheapest price is for the CXA1645, but on aliexpress AD725s are available for less than €1.40 each. If you merely wanted the SCART connector, you can send composite and s-video down the appropriate pins on a SCART cable with the AD725. But that doesn't help get you RGB if that is what you are after and it is 1 chip that is not DIP then.

the second one is that it is cheaper and also i can use Scart / Svideo connector if i don't make mistake?

By the datasheet it converts RGB analog input, to RGB analog output, Y/C, and composite, so you should be able to send all of those on a SCART connector to give maximum options.

It seems like a good idea now that I think about what you are trying to do. Sure there is an extra chip, but it's cheap, and eliminating any part that is non-DIP probably makes up for it. I am no hardware guru, but it seems like it would work to me. For the price I would pick some up and wire wrap/bread board it up to find out.

[CunningFellow]

I originally suggested to you to use a 74xx chip to divide the clock by 4x to use the other colour encoder.

But as D3thAdd3r says, that is only needed for 100% hardware compatibility. If you have the source code, you can reprogram the timer yourself.

Even if you don't have the source code, you COULD hack the HEX files to change the timer.

Comes down to what you want to do in the end and your needs. If you are making one of them on breadboard, the 74xx may be best.

If you are making a PCB and want to make it look as pure/neat as possible and don't care about 100% binary compaibility then change the timer value.

[neslou]

Yes CunningFellow, You give me some precious advice about ripple counter
I will have some try on breadboard first and of course my aim is to make pcb but with Through Hole component if possible..
I would like not to change the kernel because i am not able to do this for the moment as i am still working on the hardware side of the uzebox...
CXA1645 can be very cheap on aliexpress/alibaba.. i know that the AD725 can be samples for free as i did before..but if you want 10/20 pieces then it is more expensive..
I don't want to re-invent the wheel and compatibility is important but this is a Do it yourself scene so, if modifications are light and software it could interesting for me to investigate first, and then understand the software side of the Uzebox project like Api, kernel etc..

[uze6666]

Man, I swear I could not source DIP version of such chip 10 years ago. But now,we can find some relatively cheaply on AliExpress (which didn't exist then!). Wow, would have been exactly what I wanted...a 100% though hole project (well, ok, apart the SD card ) and not have to spend time presoldering all those damn AD725 for the kits. I'm really curious to know about the quality of the video produced by the chip, so let us know about your progress.

Even if you don't have the source code, you COULD hack the HEX files to change the timer.

And thinking about it...using a modified bootloader, you could patch standard .uze file on the fly when loading the games.