You would like a simple frequency meter that doesn’t have any front panel controls on it? Well, this RS-232 frequency meter might be your right choice!

For your information, this RS-232 frequency meter is based on Atmel AT90S2313, and the you can interacts via an RS-232 terminal program at 9600 baud. With this unique frequency meter, you can apply some straightforward code to read the 16 bit counter in the AT90S2313, where it was determined by running a timing loop through it!

In this project, you can try various approaches using interrupts from the 8 bit timer to set the counting interval. However, you’ll find that the timing will become uncertainty resulted in intolerable jitter in the measurement.

Normally, the results of the counts are mostly converted to ASCII and being sent to the terminal. By the way, you must realize one important thing here that only half the Flash ROM was used and you can fit a handy pulse generator program into the same chip.

Therefore, the result is a combined counter and frequency meter, where the chip flips between the two programs. You can controls the device and read the data via an ASCII terminal set to 9600 baud with 1 stop bit and no parity!