multi channel analog output

[sperelat]

I'm trying to make analog output pulses of microsecond order

via 3 output channels.

I try Daqmx write for that goal..and I can make single channel

pulse with pulse vi in Signal processing category

But ,I have difficulty in make pulses for more than

two channels.

When I try , Labview always make error(that I can't understand)

or do not make signal at all.

I also tried to make analog output for DC ,and it works.

I don't know,however, how I can modify this for pulses.

I will link screen captures of my labview program.

http://www.mylv.net/include/file_download.asp?file=/qna/data/PULSE.JPG&size=80854

http://www.mylv.net/include/file_download.asp?file=/qna/data/MLTI(0).JPG&size=63567

[Gabi1]

your images cannot be accessed. why not simply load the images (or even better: the vi itself) on this thread?

from what you describe it seems you know how to pule out already 2 channels simultaneously. a very first guess would be to check if you create a DAQmx task for 3 channels. also, give us the error code that you get, it will help finding the exact source. it could also be a buffer problem (not well defined).

post your vi and we can see better.

[sperelat]

I was confused..

The picture can be seen only when I'm looged on to the website

I posted message  to google  group, and I did not know that it's also posted here.

(Picture cannot be posted in google )

[Gabi1]

your problem is not clear to me.

your first pic shows output of DC to 2 channels.

your second pic shows output of a pulse for a single channel. if you want to send to more than one channel, you have to create 3 pulses, set t0 for all 3, and send the full 2D array to the DAQmx write.

[sperelat]

Thank you for your answer

I know only how to make DC output to more than one channel.

I don't know how to mkae pulses to more than one channel.

What do you mean by the term "set t0" ..?

I'm still beginner in Labview..

I also don't know how to connect more than one pulse vi to  "write vi"

I'm trying to learn how to apply DAQ vi  to my research project..but I  cannot find

detailed explanation for  multi channel analog output.

What I find is just many example code for DAQmx and  no example code

multi channel output for microsecond order

[Gabi1]

ok i made you a small application in LV 8.2

it might not work at first try, so you will have to play around and modify as needed.

you have an array that define the pulse width and relative phase for every channel (every line of the array defines a channel, in order). it is then transformed into a 2D data array, and sent to buffer.

this approach will work as long as there is a proportional relation between the rate of output and the width of pulses, to avoid underbuffer problems.

ifyou have to update lots of channels lots of times, then you might want to cycle your writing trough the buffer.

dont forget to write in the "physical adresses" control the ful list of channels used.

Message Edited by Gabi1 on 11-29-2007 01:19 PM