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Apr 2010

Beagleboard VGA output

Anonymous
Sun 4-Apr-2010 11:40
Hi,

I've been struck with a beagleboard for 6 months now( i don't have anything except VGA monitors!) and now i'm going to try this. Can you throw some light on the connections to be taken from the beagle board? Images would be of great help.

Cheers,
pracas

Craft

Anonymous
Sun 4-Apr-2010 22:51
Adorable work!

One question: I also tried using the MOSI pin to generate a video signal, but after the 8th bit is shifted out, the MOSI line stays high for a short time, before the next byte gets shifted out. How did you solve this?

Markus
lft
Linus Åkesson
Tue 6-Apr-2010 13:47
I also tried using the MOSI pin to generate a video signal, but after the 8th bit is shifted out, the MOSI line stays high for a short time, before the next byte gets shifted out. How did you solve this?

I decided to live with it. The MOSI trick is used when displaying text, either statically or in the sine scroller. In the font, every character is eight pixels wide, and the extra delay after the eighth bit forms the space between characters. The pin is connected to the video signal in such a way as to make it white when low and transparent when high.

Phasor

Swierkdeck
Thu 8-Apr-2010 20:46
Hi Linus! The more I see this demo I think it gets better! I am thinking about where did you get all that knowledge? ;)
Greetings

Beagleboard VGA output

Anonymous
Fri 9-Apr-2010 06:09
What about output current from the processor ? You plug outputs from the processor against 240 Ohm -> 7.5 mA.
Isn't the nominal current only 0.1 mA ? I have this info from the OMAP3530 datasheet.

Fratres

Anonymous
Sun 11-Apr-2010 23:01
I'm working on analyzing fratres as well, but I'm looking at the violin version. Your page has been really helpful, and I see the chord progressions now but am having a hard time with finding the different voices (since it's just the violin in the beginning). Do you know how it's laid out in the violin version? thanks so much!

The hardware chiptune project

Anonymous
Wed 14-Apr-2010 20:58
Could you please make commentary to variables and functions as description(at least for avr source?). cause its so hard to understand code.
i'm currently trying to do a simple replica of your project(on PC), but i have problems with callback. do you know books or web-pages where it's explained(how to make interrupt also).
many thanks.

The TTY demystified

Anonymous
Thu 15-Apr-2010 09:08
Thanks a lot for this great article

Beagleboard VGA output

lft
Linus Åkesson
Sat 24-Apr-2010 18:52
What about output current from the processor ? You plug outputs from the processor against 240 Ohm -> 7.5 mA.
Isn't the nominal current only 0.1 mA ? I have this info from the OMAP3530 datasheet.

Good point! I didn't think of that. This should in theory cause non-linearities, but I have looked at gradients and they look all right.

The hardware chiptune project

lft
Linus Åkesson
Sat 24-Apr-2010 18:55
Could you please make commentary to variables and functions as description(at least for avr source?). cause its so hard to understand code.
i'm currently trying to do a simple replica of your project(on PC), but i have problems with callback. do you know books or web-pages where it's explained(how to make interrupt also).
many thanks.

If you are programming a PC application, you don't have to worry about interrupts. That's where a callback function becomes useful. You'd use a library such as libSDL, and provide a pointer to one of your own functions. This function will then get called back whenever new audio samples are needed. Please refer to SDL audio tutorials.

The Swan

Anonymous
Wed 28-Apr-2010 12:32
Brilliant!

I'm curious, what do you think would be the absolute minimal platform that would perform (with voice) "Daisy Bell" originally sung by IBM 7094 in 1961?
http://www.youtube.com/watch?v=41U78QP8nBk

zws1922