how to generate a square wave with Mark and pace for 25Hz frequency for PCI-6723 card

[krishna_ak]

Hi,

    I am using PCI-6723 card from Ni for combination of DC voltage and a Hign Frequency Signals.As per datasheet of PCI-6723 says that it can generate up to 40Hz Frequency.I would like to generate a Squarewave with Mark and Space in between with a Frequency of 25Hz.I am thankful if anyone send me a sample program of a squarewave with Mark and space with frequency of 25Hz for a PCI-6723 card.

As this is very urgent requirement for my project,please help me the same.

Note :- I am using Labwindows 7.1.1 and Daqmx Version 8.0 for PCI-6723

With Regards,

krishna

[Ed W]

Hi,

Thank you for posting to the NI forums.  Although we don’t have a program that does mark and space FSK, I can give you some pointers to setup your program.

1. If you are using TTL logic, then setup a digital output task.  However, if you are using some other form of logic, then I would recommend using an analog signal to represent your digital signal.  This will give you more control over the values of your signal, and allow you to do bipolar logic as well.
2. Setup a timer function that is called every 20ms.  This will allow you to change the signal to a rising edge or a falling edge every 50Hz, giving you a maximum 25Hz signal.
3. Change the value of your signal in the timer function.

If you are trying to perform FSK, with two frequencies to represent your data, then you may need the timer function to be called more frequently.  You can set the timer’s frequency to the greatest common divisor of the two frequencies that you are shifting.  This will allow you to change the signal as often as you need for either signal, without affecting the phase.

This is just one possible implementation of a software timed FSK application.  There are many other possibilities.  Try the looking at the CVI examples in the CVI directory.

I hope this helps.  Good luck with your application.

Ed W.

Applications Engineer
National Instruments