0
\$\begingroup\$

Apparently noone ever needed anything like this on the internet because I was not able to find any example, so I hope this will become the reference question.

I need to repeat a vga 800x600 signal up to 15 meters away but can't find any decent reference for this. The signal is a CCTV dvr output signal. Commercial VGA repeaters are quite expensive ($160 each) and I'd like to be able to make one on my own.

It seems as if it is not that easy but after all it's an analogue signal, is there not any atmegaXXX chip which can repeat an analog signal on its outer pins?

All I found was examples of very poor graphic quality like below, very far from being a 800x600 color video!

low quality monitor image made with an atmel IC

\$\endgroup\$
5
  • 1
    \$\begingroup\$ Sorry to split hair in four diameterwise, but "back in the days" 800x600 was called SVGA :-) \$\endgroup\$
    – FredP
    Commented Feb 25, 2014 at 20:11
  • \$\begingroup\$ PS : unfortunately most of the atmega chips do not have DAC (except 328 I think) but anyway they are not well suited to reproduce a precise timing signal like this \$\endgroup\$
    – FredP
    Commented Feb 25, 2014 at 20:39
  • 1
    \$\begingroup\$ LT6557 in stock Digikey about $5.50/1 cds.linear.com/docs/en/datasheet/6557fa.pdf. 3 channel video amp IC. TSSOP. 400 MHz BW at 2V p-p out and 2200 V/uS :-) . [ Wow ] . \$\endgroup\$
    – Russell McMahon ♦
    Commented Feb 25, 2014 at 20:56
  • \$\begingroup\$ Following on Russell's comment.. demo board for that chip is $50. linear.com/solutions/1943 I think it's a 4-layer board, so not a bad price. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Feb 25, 2014 at 22:15
  • \$\begingroup\$ LT6557 seems to be a good candidate, however it's missing H-sync and V-sync lines! how does one deal with those? why aren't they included in the chip I/O? \$\endgroup\$
    – dendini
    Commented Feb 26, 2014 at 18:50

2 Answers 2

Reset to default
4
\$\begingroup\$

Why use a microcontroller just to boost a signal ?

A simple op-amp is just what you need.

Here is the Maxim's page for Amplifiers according to the resolution (SVGA is 800x600 ah FredP said): http://www.maximintegrated.com/products/video/amplifiers.cfm

HSYNC and VSYNC are TTL signals so a small buffer is sufficient.

VGA Electrical FAQ

\$\endgroup\$
2
  • \$\begingroup\$ Forgotten Electronics!!! \$\endgroup\$
    – GR Tech
    Commented Feb 25, 2014 at 20:58
  • \$\begingroup\$ what is the BW (MHz) inside the chip characteristics? 85Mhz 230MHz what are they? there's no explanation on their website. Am I supposed to use one say max4383 for each R, G, B line? \$\endgroup\$
    – dendini
    Commented Feb 26, 2014 at 19:02
2
\$\begingroup\$

I need to repeat a vga 800x600 signal up to 15 meters

Cable, cable and cable. You can easily find fast drivers (differential or not) but if you haven't considered the cable and how it may affect things it's going to go wrong and your picture is going to look fuzzy and the sharp edges will be affected.

Please read this: -

What Is the Maximum Length of a VGA Cable? Answer - The maximum length of a VGA cable is 9 metres; assuming the graphics card can develop that kind of signal strength. If this length is exceeded, a repeater may be required to maintain the signal quality.

You might also want to read this

It's not a total sob-story about 15m but you do need to get the best you can afford.

As for VGA repeaters - they probably digitize the signal so it can be sent 100m - are you capable of taking on that sort of project.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.