Frequency counter with a PIC16F628

This is a small frequency counter with a cheap PIC microcontroller and a few seven-segment LED digits. The main features of the frequency counter are:

*   frequency range 1 Hz … 50 MHz (prototype worked up to 60 MHz but this exceeds the PIC’s timing specifications)
* four or five digits resolution (display for example kHz, MHz, or xx.xx MHz); or 6 digits with F8FII’s modification
* automatic range switching with different gate times
* optional addition or subtraction of a frequency offset (programmable)
* optional preamplifier for the input signal
* can be built on a single-sided ‘breadboard-style’ circuit board
* firmware available for common-cathode as well as commom-anode displays
* very low component count: a PIC 16F628,
4 or 5 7-segment LED displays,
a 4- or 20-MHz crystal and a few resistors,
optionally one transistor and a few diodes to drive the 5th digit,
optionally one other transistor for the preamplifier.
* since 2006-05: preprogrammed frequency offset for transceivers with 4.0 MHz IF
(see the author’s experiences with  “Miss Mosquita”, a 40 meter QRP transceiver)
* optional (configurable) power-saving mode which automatically turns the display off
if the frequency didn’t change significantly within 15 seconds


Source: Freenet

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