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how do i interface a frequency counter with rs232


sumayya40071

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  • 5 months later...

Wow, now there is a doozer.
Lets see.

1) Use a PIC that has the RS232 as part of the hardware.  Some chips have it built in. The PIC16,17 and 18 families are good places to start.
The Smaller PIC 12 chips can also be used but you will need to download the RS-232 source code from MicroChips web site to implement the interface.  On the plus side, you get to pick the I/O pins.

2) get a MAX232 chip. (that’s the part number MAX232)  Using a few capacitors and a single 5v supply it can create the +/- 12V signal needed for the RS232 standard.

3) the RS232 on your Freq Counter is most likely a very low order interface.  SO you should be able to get by with just pins 2 and 3 plus a ground or signal return.
On a DB9 that would be 2,3 and 5 while on a DB25 it's 2,3 and 7

Electronically that’s about as far as I can help without knowing more about what you are doing.

One question though.  Unless you are counting VERY high frequencies, Most PIC chips have a built in counter that can be triggered from a I/O pin.  If you feed your signal to the chip all you need to do is disable the input, reset the counter, enable the input, wait 1 second, disable the input again, and then read the counter!
Lots easier than the whole RS-232 interface stuff.
The counters can count 16 bits on some chips and they run fairly quick.

-Mike

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