Most small function and signal generators do not have a very accurate frequency control and do not offer a built-in frequency counter. Help is at hand with the tiny frequency counter module described here, which consists essentially of just an ATtiny2313 microcontroller and an LCD panel. The microcontroller is clocked at 20 MHz, and so the counter module can be used at frequencies of up to 5 MHz without the need for a prescaler.
Resistors
R1,R2 = 390Ω
P1 = 1kΩ preset
Capacitors
C1 = 100µF 25V radial
C2,C4 = 100nF
C3 = 1µF 25V radial
C5,C6 = 27pF
Semiconductors
IC1 = 78L05
IC2 = ATtiny2313, programmed, Elektor Shop # 070954-41
B1 = 2KBP005
D1 = LED, 3mm, red
D2 = LED, 3mm, green
Miscellaneous
LCD1 = LCD module, 2 x 16 characters, e.g. Displaytech 162
X1 = 20MHz quartz crystal
S1 = miniature PCB mount switch
K1 = mains adapter socket, PCB mount
14-way pinheader, 1 row, lead pitch 2.54 mm
2 solder pins
PCB, ref. 070954-1