Official parts list

Topics regarding the Uzebox hardware/AVCore/BaseBoard (i.e: PCB, resistors, connectors, part list, schematics, hardware issues, etc.) should go here.
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kscharf
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Re: Official parts list

Post by kscharf » Sat Sep 13, 2008 4:49 pm

uze6666 wrote:
I'm thinking of maybe using the oscillator and driving the processor with an
external oscillator. This might require a change in the fuse settings, but
also might make the overclocking easier.
What do you mean by that? You have no choice than driving the mcu with the external oscillator...

Uze
The schematic shows a CRYSTAL not an OSCILLATOR module.
A crystal is just a pizo resonant element that determines the frequency of oscillation and the
oscillator is the on chip circuit of the MCU. I was talking about using a 4 pin oscillator module
that contains both the crystal and the oscillator instead.

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uze6666
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Re: Official parts list

Post by uze6666 » Sat Sep 13, 2008 10:09 pm

Aaaaah , I see what you mean. At the time I initially designed the Uzebox, there where no oscillator module of that frequency in stock. Just checked digikey and they have some now. I'm just wondering if +/- 100ppm would make any difference regarding video quality & stability...

Uze

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kscharf
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Re: Official parts list

Post by kscharf » Sun Sep 14, 2008 1:15 am

uze6666 wrote:Aaaaah , I see what you mean. At the time I initially designed the Uzebox, there where no oscillator module of that frequency in stock. Just checked digikey and they have some now. I'm just wondering if +/- 100ppm would make any difference regarding video quality & stability...

Uze
Well some of the crystals for that frequency are no better that +/- 100ppm themselves.

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Re: Official parts list

Post by havok1919 » Sun Sep 14, 2008 1:36 am

kscharf wrote:Well some of the crystals for that frequency are no better that +/- 100ppm themselves.
Yeah, I don't think the 20 vs 50 vs 100ppm or more will make a visible difference. You can be pretty sure that most home video games back in the day were using as cheap of parts as they could get without ill effect. (Color's referenced from the burst, so any error on a per line basis will be tiny.)

We're probably also talking about pixel clocks in the low ~4MHz range, so even clock jitter in the <10ns magnitude will probably be invisible. (certainly with composite out anyway).

Interestingly enough, at room temperature my Mega644 starts up and runs from a 3.3V (and even lower) supply just fine. I suspect that 5V will give plenty of margin for the clock.

I have noticed that coming out of reset might be a little iffy on power-up (depending on power supply characteristics). I might put a little R/C or a reset generator on the AVCore board to make sure we're getting a clean reset after the power rail is up.

Knowing that 3.3V @ 28.6MHz might be OK for some applications-- it might have have been better to run the pixel port as current sinks and power the output ladder from a separate reference voltage so that video brightness is independent from the power supply. (That would allow running at lower voltages for battery operation without needing to mess with the DAC resistors to compensate the brightness. You could connect directly to the output of a LiIon cell for example and have constant brightness over battery voltage without a boost regulator to 5V)... But for UZEBOX1, simple/cheap is probably best. ;-)

-Clay

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kscharf
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Re: Official parts list

Post by kscharf » Sat Sep 20, 2008 4:34 am

Analog Devices is a wonderful company.
Just got free samples from them for the AD723 and AD725 parts.
They bend over backwards and ship UPS second day air.
And they knew this was for a hobby project since I listed the 'company'
field as my ham call sign. There must be a bunch of hams over at AD.

In the past I've also requested and gotten samples of their DDS chips too for
ham projects.

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uze6666
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Re: Official parts list

Post by uze6666 » Sat Sep 20, 2008 5:43 am

Hehe that's good. Now try that with Atmel. If you get some mega1284 or xmega, or in fact anything at all, I'll send you a pack of beers (or SNES connectors, since I now have a bunch!) :)

Uze

ravyne
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Re: Official parts list

Post by ravyne » Fri Oct 24, 2008 7:21 am

kscharf wrote:Analog Devices is a wonderful company.
Just got free samples from them for the AD723 and AD725 parts.
They bend over backwards and ship UPS second day air.
And they knew this was for a hobby project since I listed the 'company'
field as my ham call sign. There must be a bunch of hams over at AD.

In the past I've also requested and gotten samples of their DDS chips too for
ham projects.
Nice! Didn't know companies were so lax about checking backgrounds like that! I tried placing my own sample order, hopefully it works and will save me a bit of scratch. I requested 2 each of the 723, 725, and an 8bit stereo DAC... not too shabby if it works I must say, its about 30-50 bucks worth of kit. Of course, I do have plans for all this stuff beyond Uzebox -- Uze has inspired me to finally take a real stab at the microcontroller-based console I've had in my mind for some time now, and hopefully I too will one day have a following and be able to produce and manufacture some units like Clay.

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Re: Official parts list

Post by ravyne » Tue Oct 28, 2008 10:59 pm

Just wanted to say to those interested that Analog has confirmed that my sample requests are being filled in full! I didn't resort to anything fishy, I gave my website name as the company name and used my website email address, and I left the "Apt." off of my apartment number, which is about as deceptive as I allowed myself to be.

To recap, I got 2x 725s, 2x 723s, and 2x 8-bit sterio DACs. Looking forward to putting these to good use!

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Re: Official parts list

Post by uze6666 » Wed Oct 29, 2008 1:12 am

Holy crap, that's about 50-60$ worth of parts no? Needless to say, Analog rocks!

Now if Atmel could do the same... I've requested samples for xMegas and mega1284 and never heard back from them... :(

-Uze

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Re: Official parts list

Post by Guest » Wed Oct 29, 2008 4:43 pm

[quote="uze6666"]Holy crap, that's about 50-60$ worth of parts no? Needless to say, Analog rocks!

Now if Atmel could do the same... I've requested samples for xMegas and mega1284 and never heard back from them... :(

-Alec[/quote]

Analog really rocks! When i started with my video game console project i requested one sample for AD725, and they sent me 2 units in no time, and i live in Brazil. Great company indeed.

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