Acquire sine wave

[cdb931]

Hello,

I'm trying to acquire a sine wave from my com1 via rs232. I don't have a DAQ, and that's where it's causing problems. I have a sine wave of around 200 hz going through an rs 232 cable into my computer. The frequency will shift between 0 and 200 hz. I pretty much have tried looking everywhere but all of the solutions seem more complicated than they should be. I'm using LabVIEW 8.2.1.
I will upload my VI so you can see. In the end, I want to replace the "simulate sine wave" with the acutal sine wave coming from the RS232. It's an analog sine wave.

[Dennis_Knutson]

You can't put an analog signal into the com port. It is not an A/D converter.

[cdb931]

But in the waveform options it has analog to digital converter.

[Dennis_Knutson]

In the waveform options of what? There are no waveform options for a serial port. A serial port is a piece of hardware on your pc. The input signals to a serial port are binary. You might want to try googling RS-232 to get an idea of how the serial port hardware (the UART) works.

[cdb931]

In LabVIEW itself when you right click and go to waveform there is an option for converting analog to digital.

[Dennis_Knutson]

Manipulating a piece of data in software has absolutely nothing do to with the physical interface you are trying to connect to. I'm guessing you have absolutely no background in electronics or computers. The serial port on a pc is just not designed to accept an analog signal and do anything with it. You might as well try to fill the gas tank on your car with coffee. Just because you can physically do it, doesn't mean that you motor will run.

[cdb931]

I might be confusing analog and digital. My english is very bad especially when it's technical, and yes I have absolutely no academic background in either subjects.

The signal coming in is in the form of a sine wave, and the sine wave is coming from 2 oscilators, which are oscillating at 9.2 megahertz and are powered by 9v batteries. One of the oscillator wires travels through a crystal which causes the frequency to shift. Then both of the wires go to a mixer, and the frequency coming out is the frequency difference between the sine waves. This frequency will always be between 200 hertz and 0. I have that connected to an rs232 which is connected to my computer.
I can convert the signal to TTL if it comes down to it. I'd just rather not.

[Dennis_Knutson]

Converting to TTL won't work either. You would really have to do a lot more work than just that to use a serial port. The simplest thing would be to but an inexpensive DAQ device like the USB 6008. There are a number of inexpensive devices from other vendors as well. If buying something is out of the question, you might be able to use an inexpensive 8 bit A/D and connect the outputs of that to the parallel port of the pc. That is TTL compatible and you have 8 data bits that can be read.