Topic: I want to build a DAC for Raspberry Pi 2

[emanuel]

hi James,


I've got a 500mW RGB + 25k sdcard laser unit (Emma Lights EM RGB 222) and a raspberry PI 2.


I want to build an DAC interface for those in order to use laserboy. Do you still ship the kit?


If yes, how can I get one?


And what 7.1 soudcard to buy ? Have you got a link?


thank's Emanuel 

[BlinkenLights]

He ships them and he may have sound cards too, if not this is the one that i think he is using (there are many "brands" but they all LOOK just like this one)
http://www.ebay.com/itm/like/331237914254?lpid=82&chn=ps

[emanuel]

@BlinkenLights


that is good. Here from Germany I could only find this one provided by lots of brands:
http://www.digitus.de/sv/produkter/multimedia/audio/usb-audio-adapter/71-usb-sound-box-da-70800/


http://www.logilink.de/Produkte_LogiLink/Eingabegeraete_Multimedia/Audio_Zubehoer/USB_Sound_Box_71_8-Kanal.htm

[James]

It looks like that will work OK.

You have front L&R, center sub surround L&R and back L&R. That's all 8 channels.

What you are really looking for is the C-Media 6206 USB sound chip.

I think that device should be OK.

James.

[emanuel]

@James thanks ,
I've found C-Media 6206 USB sound chip is inside.

And what about the amp kit? Do you still sell them?

How can I get one?

[James]

Yes. I still sell them.

I can put one in an envelope and weigh it. Where are you in the world?

The kit is $40 plus shipping.

What are you looking for in this forum? Maybe I can help.

James.

[emanuel]

fine, what is the best way to pay? 

Im from Germany (Bavaria)

I'm looking for a lot n this forum because I'm very new to RGB Lasers, real galvanos and ild.

In the late 80's I've played a lot with my NeHe + C64 + interface + positioning mirrows and other effects. In thouse days it was impossible for me to buy such things...

2015: The RGB is a nice toy. I've testet from sd card and from qlcplus (DMX), but this is all limitted to ttl at this time. For me as hobbyist it is not intresting to buy pangolin ...

I'm using Linux since the late 90's so LaserBoy is my favorit choice.

Also the wave file idea is very cool, because  qlcplus can start extern exec from macros. But first of all I've to learn more about the LB sw (setting for ~25k, ...)

a pic off my qlc laser test console:

[James]

Ok.

Well, my first suggestion would be to get a nice inexpensive US English USB keyboard.

I put some thought into laying out the keys that make LB work. If you have a German keyboard, some of the glyphs might be in different places. Not sure about that.

There are some settings in the [Tab] menu and some in the x menu. [Tab] is where the value settings are and x is where the on / off settings are.

Of interest are the max lit distance and the max blank distance in points.

ILDA file standard vector images are made of 3D (or 2D) vertices stored as 16 bit signed integers. So space is a cube of 65536 points. If you consider the point (0, 0, 0) to be the center of space then you can forget about -32768, because there is no positive 32768!

So these max distance values are relative to that space. That is to say LB will interpolate points along straight lines and add points such that none of them are father apart than these values.

This is ultimately what controls the velocity of the scanners.

If each point is translated into a sample in a wave file and the sample rate of that wave is 48KHz. this is how far the scanner is expected to move in 1/48000 of a second.

If you are preparing art for that SD card reader, you should probably change the wave sample rate to something like 20000 or 25000 to match the DAC rate of the SD card reader.

You can also figure on increasing the distance between added points as the scanner will have a longer period between DAC cycles.

If you plan on using LB to optimize your art and save that as ILDA, you need to turn off the automatic minimization process in menu x. Otherwise LB will strip out all of the optimizations in your art and save a file of minimal size.

Another factor in the [Tab] menu is max dwell in microseconds. Since this value is time, it is relative to the wave sample rate setting. This factor is used to determine how long (how many samples) to sit in one place in corners of your image. The more acute the angle is, the more dwell points will be added. A full 180 degrees is the most acute any angle can be. Dwell gives the scanners time to come to a complete stop before moving off in another direction, so you see a nice clean angle rather than a sloppy curve.

James.

[emanuel]

german keyboard work typing correct keys. As I've compiled LB on ubuntu host? 


but setup ild for sdcard or iShow-prog-import-test still do not work. 


I'll will try again...

[James]

OK! I just sent you a built LaserBoy Correction Amp board.

I hope you get it soon. Let me know.

In the mean time we can work on the sound card that you have to get it ready for the correction amp.

Can you post some pictures of the sound device you have?

I would suggest using insulated solid copper telephone wire. I like to use red and black for the +5V USB power and the ground and then I use white, gray, red, orange, yellow, green, blue and violet for the direct outputs of all of the DAC channels 1 through 8.

If you use this solid copper wire, you can push it into the pin sockets of the correction amp inputs.

They hold quite well and this gives you the ability to swap out the channels that are different between Windows and Linux.

You will find that the default order of wave channels to DAC channels is different between Windows and Linux. Channels 5 & 6 are swapped with channels 7 & 8.

You might also find that channels 1 & 2 (X and Y) are also swapped on the sound device itself.

Once you find the decoupling capacitors for each DAC channel you should tack a wire onto the positive signal side of each cap.

http://laserboy.org/forum/index.php?topic=8.msg6336#msg6336

With the sound device driver loaded in your OS, make sure the device is enabled for 8 channels of output.

In Windows, there is a control panel for the device driver. There you can specify that it is an 8 channel device. You also need to set up the Windows sound system to use 8 speakers.

You'll need to do some research to make sure the device is set to 8 channels in your version of Linux.

With no sound playing, you should be able to measure a small DC offset voltage on each of the direct outputs of the DAC; like +1.2 to +2.25 VDC with respect to the sound device ground.

This is the DC offset that the correction amp is designed to NULL out.

In LaserBoy there is a setting to invert wave output. This is the default setting. This means that positive numbers from the vector art; galvo positions and color signals, will be saved as negative numbers in the wave. This is because the correction amp is an inverter; negative times negative is positive.

So, if you make a wave file of frame 10, the big white circle, in LaserBoy, when you play it, you will see the voltage drop low on the color channels. You should also be able to measure some AC voltage on the galvo channels.

So, let's get to that point before we go on to adjusting the correction amp that you don't have yet.

James.

[emanuel]

I'm still waiting for it! 

[James]

That sux.

This might help. I don't know if this works outside of the USA, inside of Germany, but here is the tracking number.

LC689247211US

It went out via USPS Customs form CN 22 on 07/09/2015 15:28

I just checked it online and it says that tracking is not available to Germany.

So that must mean that it is no longer in The USA. It must be in German Customs.

James.

[emanuel]

hope so, yes, I've tested it, no tracking from Germany posible.

[emanuel]

It was yesterday in the mail 

[James]

Awesome!

Do you know how to adjust it?

James.