can I overcome delays on implementing digital output using DAQmX

[Spurious]

Hi

I am using an X series USB Daq (6341) witn Labview 2010.

My application writes a digital output and then waits for a response. If the response is negative after a certain time a different value will be written to the output  and this loop continues until a a postive response is recieved. Now I have noticed some odd things happening.

I am using On demand timing which seems to take about 2 mS to actually output the values (using the DAQmx vis Digtal Write 1 line 1 point or Digital Write N lines single point)  This is the major delay in my feedback loops and why the execution of these vis takes so long I dont know.

To attempt to overcome this problem I instead wrote a sequence of digital outputs as a waveform with a significantly faster rate and attempted to synchronise the feedback system so that I knew which member of the sequence was the correct value. This would work fine except for one problem - there is a huge delay that occurs (>100ms) before the waveform actually appears on the lines after issuing the  Digital Write Waveform vi. . This method requires a different setup using the sample clock timing source and defining the rate and the output sequence is certainly correct and rapid, just much too late. I have ttried playing around with the buffer size etc but to no avail.

Has anyone else experienced these difficulties?

Does anyone know how I can either reduce the time it takes for the on demand vi's to execute, or how I can prevent the waveform from suffering these large delays before being issued  to the lines?

[Christian Mergl]

In my opinion it is the wrong hardware for this task. I would use an FPGA board.

Christian