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Topic: Simulating VGA Signal (Read 12208 times) previous topic - next topic


I want to know too how to send some RGB signals, just some lines f.x.??


hey guys,

sorry for reopening this thread again and again but this seemes the most relevant thread on the vga topic. i just wanted to know if someone of you really gettings things done? it seems that i got sync working with the code of dwan, but how sending signals is a bit confusing me. can someone post an example on how you managed sending colorsignals and how you connected the vga cable? i am bit confused about conecting the mass cables of the vga, are they all conected to grnd?

has someone atached the sending of color information to dwans code?

i am getting quite desperate about this whole thing.


Feb 22, 2010, 07:55 pm Last Edit: Feb 22, 2010, 08:34 pm by dwan Reason: 1
Hi there
Actually, i have another arduino sending the colors.

In order to generate the colors, i used 3 TLC5940, 16*3 homemade vactrols, and 16*3 low-pass filters. The TLC can generate 16 PWM waves, running into LEDs, facing LDRs, going thru a LPF, part of a voltage divider, running into an opamp. I would certainly simplify this if i had to make it again, but i was running out of time and used only things that i knew they were working.

You have to know that the color signals must occur only when you're supposed to see colors on the screen. I've spent days to figure that  ;D, just because I thought that the screen was "reading" color values when it needed. It means that the second arduino (color manager) has to be aware of when it have to send colors, and when not. Luckily, i found a video-purposed opamp (AD813ANZ) that makes it easy to do, because it has three "disable" pins. These pins are plugged to the pin of the first arduino (sync manager) that is LOW when color can be sent, and HIGH otherwise. That's the purpose of this special pin.

Concerning the ground cables, i soldered them all together, as i was using the same ground reference. You have to do some experiments, as i had sometimes to deal with noise. I used CAT5 cable (8 wires, cheap and reliable), so i had not that much possibilities for wiring. I had to make 16 cables, 6.5m each, worked well. Using the same ground or not depends on if you use the same ground ref for sync and colors. If i remember, each wire (2 syncs and 3 colors) has its own ground wire, so it means that you could send 5 signals with 5 differents ground refs : the screen would accept, as it's isolated (that's the assumption i made ;D )

Picture of the beast :


hey dwan thanks for your reply. your beast looks amazing.
do you think that it is possibel to sync two arduinos without an extra ic?
are there examples of what your videosynth generates?
i managed to get the code of YenTheFirst run, with his help,
to generate both sync and colors with one arduino.
until now the sync doesnt work realy nice, so i have to do some tests.
does someone know if there is an trick to generate random values on low level assembler base.
or is it possibel to speak to random pins? switch it on and of randomly?


Thanks :)
Well, i guess you can use the serial ports to sync two arduinos, but since you're doing something both time and data critical, it won't be easy : that's why i'm using two arduinos : one to manage the serial link, one to generate the interrupt-intensive sync signal. I tried with only one arduino (generating color and sync, and handling midi messages) but it would lose either bytes or sync ;D

This videosynth only generates plain colors (127³), no fancy stuff. It's controlled via midi, with a Pure Data patch.

If you want to address random pins, you could read the value of a floating analog pin.

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