I'll give you a circuit, the signal shaping circuit I just drew for you, and then output it to T0 of single chip microcomputer for counting, and then give you a digital frequency meter program, AVR's.

# Contains? & ltIOM 16v . h & gt；

# Contains? & ltmacros.h & gt

# Definition? Ucal? Not signed? tea

# Definition? uint？ Not signed? Internationalorganizations (same as international organizations)

Ucal? led_7[ 10]={0x3F，0x06，0x5B，0x4F，0x66，0x6D，0x7D，0x07，0x7F，0x6F }；

Ucal? position[8]={0x7f，0xbf，0xdf，0xef，0xf7，0xfb，0xfd，0x Fe }；

Ucal? dis _ buff[8]； //? The display buffer is used for storing the segment code value of 8 characters to be displayed.

Ucal? Hypothesis;

Ucal? time_ 1ms_ok，display _ ok = 0；

Ucal? time0_old，time0_new，freq _ time

uint？ freq

Invalid? Show (void)//? Dynamic scanning function of 8-bit LED digital tube

{?

PORTA？ =? 0xff

PORTC？ =? led _ 7[dis _ buff[posit]]；

What if? (posit==5)？

PORTC？ =? PORTC？ |? 0x80？

PORTA？ =? Location; ?

What if? (++posit？ & gt=8? )?

Hypothetically? =? 0;

}

//? Timer? 2? Output? Compare? Interrupt? Service? routine

#pragma？ Interrupt handler? Timer2 _ ISR: 4

Invalid? Timer2 _ ISR (invalid)

{

time0_new？ =? TCNT0？ //? 1ms records the current count value of T/C0.

time_ 1ms_ok？ =? 1;

Show _ok? =? ~ display _ ok

What if? (display normal)

Display ();

}

Invalid? freq_to_disbuff(void)//？ Convert the frequency value into BCD code and send it to the display buffer.

{

Ucal? I，j = 7；

For what? (I = 0； I < = 4; i++)

{

dis_buff[j-i]？ =? freq？ %? 10;

freq？ =? freq？ /? 10;

}

dis_buff[2]？ =? freq

}

Invalid? Major (invalid)

{

Not signed? Charles? Me;

DDRA = 0x ff； ? //? LED digital tube drive

DDRC = 0x ff；

//? T/C0 initialization, external counting mode

TCCR0 = 0x06？ //? External T0 pin falling edge trigger count, normal mode

TCNT0 = 0x00

OCR0 = 0x00

//? T/C2 initialization

TCCR2 = 0x0B？ //? Internal clock, frequency division of 32 (4M/32= 125KHz), CTC mode.

TCNT2 = 0x00

OCR2 = 0x7C？ //? OCR2？ =? 0x7C( 124), (124+1)125 =1millisecond.

TIMSK = 0x80//? Allow T/C2 comparison matching interrupt

For what? (I = 0； I < = 7; i++)？ dis_buff[i]？ =? 0;

Time 0 _ Old? =? 0;

ASM(“sei”)； ? //? Open global interrupt

What time? ( 1)

{

What if? (time _ 1 ms _ok)

{? //? Cumulative T/C0 count value

What if? (time0_new？ & gt=? time0_old)？ freq？ =? freq？ +? (time0_new？ -? time 0 _ old)；

Or what? freq？ =? freq？ +? (256? -? Time 0 _ Old? +? time 0 _ new)；

Time 0 _ Old? =? time0 _ new

What if? (++freq_time？ & gt=? 100)

{

freq_time？ =? 0; ? //? 100 ms to,

freq _ to _ disbuff()； //? Send pulse count value display in100 ms.

freq？ =? 0;

}?

time_ 1ms_ok？ =? 0;

}

}

}