Why USB?

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08-08-2008, 13:52
Danny

Why USB?

Hi! I'm just wondering about a few things. Why is everyone using USB DAC's? Hooking up two DAC0832's to the printer port is very simple and works fine. I know that it may be hard to have full color and such features but for me and some others using single color simple systems it would be easier and cheaper. There seems to be no open source USB DAC's either... I'm still waiting for "Spaghetti" to support DAC0832 as promised. I may be waiting in vain since it seems that the trend amongst most software programmers is to skip the DAC0832 support in new versions of their software. I'm just a cheap hobbyist and I don't want to spend a lot of money on a DAC that I could make myself. I'm seriously thinking of skipping the PC and run all my shows from a SD card...

Don't say that the old printer port is to slow now.
30kpps @8bits => 30k * 2 * 8 = 480kbit/s
The ECP specifies 2.5Mbit/s transfer speed and this shouldn't be a problem even for an older PC...

I'm using Norms software at the moment but that is so full of bugs that its barely usable... It also nearly freezes my old p3 1000. Seems to run smoth on my core2 machine but it really shouldn't need all this processing power to run...

Just felt like whining a bit :)
08-08-2008, 14:25
DZ

I think one of the problems we've seen at the laser meets, is that parallel port DAC's have sample jitter problems. Perhaps the problem could be rectified with a well designed parallel port DAC, but another problem, is that alot of laptop's these days don't even have a parallel port! So a DAC on the USB port seems to work well and just about every computer now has a USB port. Of course the best bet is to have a QM2K with a .NET board.>:)
08-08-2008, 14:26
badger1666

dacs

yep been there too ,printer port just take up to much proccesor time and gives priority to sending data to ecp and not enough time to the program trying to supply data to it and causes lot of system crashes so you need somthing over 2ghz or core duo so one core can run the printer port and the other the software,so everyone switched to less cpu intensive usb but i still like the old alphalite dac compared to my fb3 :)
08-08-2008, 19:56
Things

I was told to stay away from printer port DAC's , not because of the speed, but simply because the printer port is low priority on computers. So if your CPU starts working on something during a show, you could end up with a static beam!
08-08-2008, 22:21
barold

i dont have a printer port :(
08-08-2008, 23:11
highvolt

I would rather see ethernet dacs in stead of usb... cablelength is not limited to 5m like usb, works on all operating systems... no driver needed. etc...
08-08-2008, 23:13
Things

Neither do I. It was a pain when I was out buying a DMX controller. There were alot of easy printer port ones, but the USB one was $256AU. I ended up going with the USB, and I dont regret it, its a damn well build little controller! Ive dropped it on the floor once ( Accidental of course.. ) and the thing still worked afterwards! Eventually no computers will have a printer port, as more and more printers are becoming USB aswell there is really no need for them anymore
08-09-2008, 02:12
afrob

Quote:

Originally Posted by Danny

There seems to be no open source USB DAC's either...

Take a look at bILDA http://www.linux-laser.org

Greetings,
afrob
08-09-2008, 04:54
carmangary

Jitter is a good reason not to use the DAC0832 DAC but that is not what Spaghetti doesn't already support it. The reason that Spaghetti doesn't support the DAC0832 parallel DAC is because of the timing issues. It's pretty easy to send a set of points and a point rate to a USB DAC. The USB DAC takes care of making sure that points are at 30000pps or whatever is specified. The LPT DAC won't do that, though. It's up to the computer to send each point to it at the correct rate. 1/30000 = .033msec. The resolution of a Windows timer or Sleep command only goes down to around 1 to 20 msec! So, in order to time things correctly, the system clock ticks have to be counted and the only way to do that is to do a tight loop that does nothing but count ticks. When you do that, CPU usage goes through the roof and leaves much less processing power for doing things like playing music or computing the next frame. It just isn't a good situation and will be evident when you try to open a file while playing a laser show and everything goes to crap.

Now that LaserBoy and DrLava have teamed up to create a soundcard mod kit and driver, it's just as cheap and easier to build a modified "LaserBoy" sound card DAC as it is to build a DAC0832 DAC now and it will work a lot better. For that reason, I really don't have much motivation to add support for the DAC0832 DAC. I will be happier not supporting it and I am sure anyone would be happier with the Sound Card DAC.

But honestly, the best thing to do is just to save up a little money and buy yourself a real DAC. In the end, they are a lot less headache and may offer other features. I have been playing around with my new Riya DAC and it's nice. It supports up to 2GB of SD card ram so I can put a lot of shows on it and let it run on it's own. Perfect for my Halloween show on the side of my house. :) You'll never be able to do that with a soundcard or a DAC0832 DAC.

That said, I may still add support for the DAC0832 someday but don't hold your breath waiting for it. Actually, I have already written a driver but it needs updating to work with my new code. But, I blew up my test DAC by hooking up voltage backwards and need to fix it before I can test anything. haha.
08-09-2008, 04:59
carmangary

Quote:

Originally Posted by highvolt

I would rather see ethernet dacs in stead of usb... cablelength is not limited to 5m like usb, works on all operating systems... no driver needed. etc...

My new RIYA DAC supports ethernet. I haven't tried it out, yet, though. I need to do that and add support for it in Spaghetti. But, you are wrong about no driver required. There will always have to be some sort of driver that formats the data into the right format before sending it across the wire.
08-09-2008, 05:59
riyalasers

Gary,

Quote:

Originally Posted by carmangary

My new RIYA DAC supports ethernet. I haven't tried it out, yet, though. I need to do that and add support for it in Spaghetti.

For Ethernet support for our controllers you should not make any additional options in Spaghetti:
- in directory where is Spaghetti make please network.ini file with IP address of controller.

IT IS ALL!!!

Connect controller by Ethernet, run Spaghetti, and it will work!

All the best
Ihor
08-09-2008, 12:57
tigerpaws

Quote:

Originally Posted by riyalasers

Gary,

For Ethernet support for our controllers you should not make any additional options in Spaghetti:
- in directory where is Spaghetti make please network.ini file with IP address of controller.

IT IS ALL!!!

Connect controller by Ethernet, run Spaghetti, and it will work!

All the best
Ihor

you cant beat simplicity
08-11-2008, 14:05
Danny

Thanks! You all presented good reasons for not using a printer port based DAC. I'm actually not using DAC0832 but rather a DAC0832 compatible circuit with two 10-bit serial DAC's and a microcontroller. I was planning to add SD memory support in the near future to make my homemade projector fully portable (runs of built-in 12VDC lead acid battery). I have had problems reading the printer port data as it is full of noise. The timing is also a big problem. The points are not evenly spaced in time wich makes some points brighter than others (actually looks kinda cool... =) ) If I move my mouse around a bit it shows on the projected image... Haven't tried opening any files while projecting as it would just cause chaos :)

I think I will leave my printer port interface and just add SD memory capability. That would solve timing and jitter issues and also let me use 10bits resolution. I know abut the bILDA project but I need windows software as I don't have any Linux knowledge at all. I guess I could learn but I don't have the energy to spend a lot of time just getting the PC booting the operativ system...
08-13-2008, 09:06
keeperx

Quote:

Originally Posted by barold

i dont have a printer port :(

BINGO!

New laptops dont have prionter ports and new desktops are starting tleave them out.

Mac does not use parallel but windows, linux, and mac all use USB.

its UNIVERSAL serial bus.

i agree with the ethernet thing, and even more so with an 802.11x dac..
08-13-2008, 09:27
riyalasers

For work via Wi-Fi is nesessary only Wi-Fi access point (~$40), and controller with Ethernet interface...

Ihor
08-13-2008, 11:01
keeperx

yeah i know that, but a dac that was wireless by design would be nice
08-13-2008, 11:18
riyalasers

Wi-Fi acces point (usualy) cost about $40
Wi-Fi access point (oem version) - 2-3 times expensive.
Will you pay more?
08-13-2008, 11:44
keeperx

i dont.. i built my dac.. but it would be a great commercial product.
08-13-2008, 13:04
heroic

Quote:

Originally Posted by Danny

(Linux) I guess I could learn but I don't have the energy to spend a lot of time just getting the PC booting the operativ system...

It takes about twenty minutes to install Linux these days... Ubuntu et al have made huge steps towards making Linux ready for the nontechnical user. You should check it out!