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How do I ramp a digital output frequency

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I am using Labview 6i with a PCI-6601 board.

I need to apply a linear ramp to an output frequency on a digital TTL
output; in order to accelerate the speed of a stepper motor. Is there a
method by which this ramp can appear continuous, seamless?

Currently, with each update in output frequency, there is a pause (some 5ms)
where the digital output -counter is being re-initialised with the updated
value.

Thanks
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Hello Mark,

I found an example that does exactly what you need by going to zone.ni.com, and then searching for "counter and fly". This search pulled up an example with the following description:

This example is a Pulse Width Modulator in LabVIEW, which allows you to change the frequency and the duty cycle of a TTL pulse train generated on a Counter with out reconfiguring the board (on the fly). This VI takes advantage of the NI-TIO chip on the PCI-6602 board, but also works on the E-Series boards using the DAQ-STC chip. The subVIs that are included are modified versions of the DAQ 6.5.1 counter VIs. They are modified to acount for adjacent counters with the NI-TIO chip. When using an E-Series board and low frequencies, you are restricted to changing the pulse specific
ations only once during a given cycle.

The URL to the example is attached below. I hope this helps with your application!

Best regards,

Michael

http://zone.ni.com/devzone/devzoneweb.nsf/opendoc?openagent&80CBEDEA62F023C58625683A000BA5A5&cat=FF385ADC3E7A8C8A8625679000743B6F
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