Can I plug a TTL signal into the mic on my sound card?

[NIquist]

Yes but serial port lines expect positive voltages between +3 and +15V for a 'high' (which TTL does provide) AND negative voltages between -3 and -15V for a 'low' (which TTL doesn't provide).  It might just work but it might not and worse, it might be flaky if it does.  A simple circuit could translate the voltage levels but it will need power.  Don't you have a parallel port too?  That's easy to interface to with TTL.

[josborne]

Thanks, NIQuist.

The PC does have a parallel port.  So it looks like I could wire that TTL signal to one of those pins and then read it. 

I'll take a look at the link and try it out.  Though I wonder now if its easier to just spend the $99 and wait for one of those USB DIO cards.

Thanks!

[NIquist]

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@josborne wrote:

  Though I wonder now if its easier to just spend the $99 and wait for one of those USB DIO cards.

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No need to wonder... It's definitely easier!

Spending money usually is.

[Greg_S-Video]

Hello Josborne

I would like to be able to help you with this issue.  I'd apprecite if you could answer some questions for me.  What is the "high-level" application of this project?  Who is the producer of your sound card and what is the model number?  I experimented with using sound cards as DAQs and found that the input I was using was filtered for signals between the range of 20 Hz to 20 kHz (human speech).  This adversely affected the measurements. 

In addition, you may consider posting this topic in our DAQ message board:
http://forums.ni.com/t5/Multifunction-DAQ/bd-p/250

As well, I can put you in touch with a representative who may be able to assist you in addressing your needs and pointing you to a DAQ device sutiable for your needs.

Please don't hesitate to let me know or ask any questions.

Thank you for your support of National Instruments Corporation.

Greg S.