FREQUENCY METER
Free for educational and noncommercial use ! ! !
For commercial use you must contact the author ! ! !
DESCRIPTION: Very acurate frequency meter. Base module 0 - 50MHz and with prescaler (1/100) over 1GHz (1243 MHz as I measured). There is no design flaw in this frequency meter. It is precise even up to 1 Hz measuring 50MHz. Precision depends only on quality of components that you are using. Only thing you can do is to add a thermal stabilisation on crystal... :D
PRINCIPLE of measuring: Input is connected to T1CKI. Prescaler is 16bit who is able to count up to 50MHz and it doesn't have effect on microcontroller's instructions... It just counts input inpulses.
SOFTWARE for PIC16F877: Program code is written using MikroC and it is simple. When 1second of measuring is passed, than in same time input gate is closed and interrupt occures on RB0. PIC is geting counters state, calculates, displays data on display, resets counters and than resets external time base to begin new cycle of counting. Program size is 1,2 KB and is within 2KB demo limit size of MikroC...
Links to some usefull web sites.
7 segment LED display version of frequency meter.
Donations are appreciated.