Frequency Counter and Timer

In counter mode it provides 1Hz resolution up to 100Mhz. In timer mode maximum resolution is 0. 0000001 Hz up to 1Hz. Resolution is reduced by one digit for each additional decade. Multiple frequency updates per second by employing a sliding window for calculation. In case the AVR should be programmable in circuit, a few modifications must be made. In essence all
Frequency Counter and Timer - schematic

third parties on wires used for programming are isolated using 47k resistors. The resistors in combination with Mega8 gate capacity create a low pass. This is software compensated using increased settling time for the external counter. This picture shows the test board with the full counter circuit except the 7 segment LEDs. Those are already mounted and soldered on a separate board. The wires on the top right connect to it. (One connector for digit selection and one for the actual 7 segment code. ) This is the final board that will be put into the device. It has connectors for power, 7 segment code, digit selection, in circuit programming and TTL signal input.

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