lf253 Frequency counter 1Hz-100Mhz with LCD display and RS232 interface

Posted on Feb 5, 2014

This article continues the AT90S4433 Microcontroller series. I suggest you to read the previous articles on Atmel Microcontroller programming with regards to: This time we design a frequency counter which can measure frequencies from 1Hz to 100MHz. Alternatively you can use it also to just count events, such as how many people crossed the street (

lf253 Frequency counter 1Hz-100Mhz with LCD display and RS232 interface
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what ever is available as a digital pulse). The counter has a LCD display as well as a RS232 interface to read out the counter results from Linux. The frequency of a sine wave or square wave signal is expressed as the number of oscillations per second. In order to determine the frequency of a continuous signal one just needs to count those oscillations. This way we determine the frequency of the first harmonic of a continuously oscillating signal. To measure the frequencies that a non continuous "sound" is composed of, you need a spectrum analyser. This is however a different piece of hardware. What we design here is a frequency counter for continuously oscillating signal. We assume that the signal does not change its frequency during a given interval where we sample the signal. 1 x MAX903 high speed voltage comparator, 8 Pin plastic DIP package, you can order it directly from in case your local dealer does not have it in stock. All LCD displays that I have ever seen with 14 or 16 pins on the connector were HD44780 compatible. You can also use a 3 or 4 line display but then you will need to modify the software a bit. In addition to that you need some wires, connectors (BCD, power, RS232) and a 9V transformer or some other AC or DC power supply (150mA). Sometimes you get very cheap power supplies which plug directly into the wall socket and are used for all kind of consumer electronics. I used eagle for Linux to design the...

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