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VGA clock with USB interface
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Date: 2006/08/03 17:25
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By: Mat
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Status: Admin
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Karma: 7
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This thread discusses the Content article: VGA clock with USB interface
Thanks Dario for the new article!!
Mat
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Re:VGA clock with USB interface
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Date: 2006/08/09 08:24
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By: dariog
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Status: User
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Karma: 6
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| Posts: 107 |  |
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Coming soon: doubled resolution, now we can have up to 64 x 32 pixels (and possibly 64x64...) and the ability to change clock-color on the fly (i.e. no longer hard-coded)
Some code optimization too..
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Re:VGA clock with USB interface
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Date: 2006/10/10 08:19
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By: dariog
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Status: User
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Karma: 6
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OK, here it goes the new firmware release.
The prototype is now up and running since august, and works rather fine. The self-running clock was a bit late (losing 3 minutes in an hour) so the divider has been corrected and now is more precise); Main softwareon the PC updates the VGA clock from the atomic clock on the internet (time.ien.it) once in an hour, so it never goes too wrong; USB interface seems to work correctly (on a Windows 2000 server), though, on a warm reboot, at times the USB is not found and you have to replug it (annoying, although quite rare). A FIX for this rather typical problem must be found!
Besides, we've got software-customizable display color on-the-fly (just send a particular packet to US between Red-Green-Blue.
And we have doubled resolution, i.e. 64x32 pixels (actually, it's 4-times cmpared to earlier version). It can be choosen at compile time. Be aware of some increased flickering!
File Attachment:File name: vgaclock.zipFile size:185792 bytes
Post edited by: dariog, at: 2006/10/10 09:19
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Re:VGA clock with USB interface
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Date: 2006/11/15 22:58
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By: dariog
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Status: User
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Karma: 6
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...and made my version.
TV bar generator, capable of some 64x48 pixel (4:3 ratio), with 4 grey levels.
Uses a 18F2550 overclocked at 50.302 MHz (12 times Chroma frequency, in order to be able, maybe one day, to have some PAL features, i.e. colors!)
A simple R-2R is used as a simple DAC to have the 3 levels needed for this video signal.
C code with some mixed assembly; signal is generated in interrupt.
Uses: TV linearity tester...
Base for games, Images displaying (with a SD connected).
Theorical upgrades: reaching for 16 grey levels is feasible, yet it would consume almost all of the RAM (on this PIC): depending on the use and the other peripherals needed, one can switch to another PIC.
8 levels i.e. 3 bit is of course impraticable due to opcode oddity in handling 3 bits a time!
Higher horizontal resolution could probably be achieved, and so vertical: once again, the limit is the available RAM. 
Post edited by: dariog, at: 2006/11/15 22:59
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Re:VGA clock with USB interface
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Date: 2008/04/30 02:29
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By: Jonathan
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Status: Visitor
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The EUSART could be useful for e.g. text overlays, as seen in Linus Akesson's Craft demo. You might need to add a few resistors though.
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Re:VGA clock with USB interface
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Date: 2008/05/02 03:35
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By: roger
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Status: Visitor
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hello ....
i am very interested in this project. the link is dead for the updated firmware.
can someone please email it to me at : tecfacet @yahoo.com. (remove space) from email address.
thank you,
roger
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