Circuit Lake

Electronic Project and Circuit Collection

RS232 Frequency Meter and Pulse Generator

03/15/2010 Category: AVR, Measurement, Project, Tools

This multi purpose project is built around MCU AVR AT90S2313. Besides as Frequency meter, the project can be used as Pulse Generator too (combined counter and frequency meter). It doesn’t have any front panel controls because the user interacts via an RS-232 terminal program at 9600 baud. The user controls reads data via an ASCII terminal set to 9600 baud, 1 stop bit, no parity. It use a terminal emulation program named “Term.exe”. The input and output are via the same terminal.


The firmware is straight forward code to read the 16 bit counter in the AT90S2313 after period of time, which was determined by running a timing loop, said Richard Cappels, the designer.

Pulse Generator Features

  • 10 us to 65.5 ms pulse period
  • 5 us to 65 ms pulse width
  • 3 bits of selectable pulse amplitude (2^3 binary coded amplitudes). You design the ladder network for your needs.

Frequency Meter Features

  • Counts to 65536 (all you can get from the 16 bit counter on the ‘2313)
  • Selectable time base of 0.1, 1.0, 10, and 100 seconds.
  • 4 Mhz max frequency (this can be increased if you change the crystal and rewrite the timing loops for both sections of the code)

SchematicASM fileHex File

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