C source program design of AT89C51 microcontroller frequency meter

This article is the C source program of the frequency meter based on the AT89C51 microcontroller. The main functions of this frequency meter are as follows:

1. Test function

It indicates all the test functions possessed by the digital frequency meter, generally including frequency measurement, period, accumulated pulse number, frequency ratio, time interval and self-comparison functions.

2. Measuring range

It describes the valid measurement ranges of different functions. For example, when measuring frequency, the measurement range is the frequency range of the measured signal when the digital frequency meter is under normal working conditions. It is generally expressed by the upper and lower limits of the frequency. Most of the low-end starts from 10Hz; the high-end varies depending on the frequency meter. different. Therefore, the high-end frequency is the basis for determining low, medium, and high-speed counters. When measuring the cycle, the measurement range is expressed by the maximum value and minimum value of the common cycle.

3. Input characteristics

Digital frequency meters generally have 2 to 3 input channels. When testing different items, the measured signals can be input to the instrument through different channels. Input characteristics are a set of characteristic parameters indicating that the digital frequency meter is connected to the signal source under test, and usually include the following aspects.

(1) Input sensitivity. Usually refers to the effective value of the minimum input voltage that the instrument can operate normally. The sensitivity of commonly used digital frequency meters is around 100mV.

(2) Maximum input voltage. Refers to the maximum input voltage value allowed by the instrument. If the measured signal exceeds this value, the instrument cannot guarantee normal operation and may even be damaged.

(3) Input coupling method. The instrument is configured with two coupling modes, AC and DC. When AC coupling is used, the signal to be measured is input through the DC blocking capacitor. When DC coupling is used, the signal to be measured directly enters the input circuit. AC coupling is suitable for measuring signals with DC level, and DC coupling is suitable for measuring low-frequency pulse or step square wave signals.

(4) Input impedance. In order to reduce the load on the signal source, digital frequency meters generally use high-frequency input impedance. Input impedance consists of two parts: input resistance and input capacitance.

4. Display and working mode

It indicates what can be displayed, the number of digits displayed, the display device used and the duration for displaying the measurement results after a measurement is completed. Some also explain that the electronic counter has a "non-memory" display mode or a "memory" display mode.

5. Output

There are several standard frequency signals that the instrument can directly output, and it can indicate the encoding method and output level of the output measurement data.

C language program

　　#include

　　#include

　　#define uchar unsigned char

　　#define uint unsigned int

　　fly temp［8］={0，0，0，0，0，0，0，0};

　　fly temp1［8］={0，0，0，0，0，0，0，0};

　　fly T1count，timecount，T1count1，timer，yushu，yushu1;

　　long fre，frx;

　　float zhou;

　　bit flag;

　　bit flag1;

　　void delay（flying）;

　　bit result;

　　sbit ird=P1^1;

　　sbit id=P1^0;

　　sbit clr=P1^2;

　　sbit en=P1^5;

　　sbit rw=P1^6;

　　sbit rs=P1^7;

　　sbit rd=P3^7;

　　sbit kb=P1^3;

　　sbit kx=P1^4;

　　sbit A0=P3^6;

　　sbit A1=P3^7;

　　bit start;

　　flying code tab1［］=“fre： ”;

　　flying code tab2［］=“frx： ”;

　　void delay（flying z）

　　{

　　fly x，y;

　　for（x=z;x》0;x--）

　　for（y=110;y》0;y--）;

　　}

　　guide_bz()

　　{

　　rs = 0;

　　rw = 1;

　　in = 1;

　　result = （bit）（P2&0x80）;

　　in = 0;

　　return（result）;

　　}

　　void write_com（uchar com）

　　{

　　while（bz_guide（））;

　　rs = 0;

　　rw = 0;

　　in = 0;

　　P2=with;

　　delay（5）;

　　in = 1;

　　delay（5）;

　　in = 0;

　　}

　　void write_dat（uchar dat）

　　{

　　while（bz_guide（））;

　　rs = 1;

　　rw = 0;

　　in = 0;

　　P2=that;

　　delay（5）;

　　in = 1;

　　delay（5）;

　　in = 0;

　　}

　　void init（）

　　{

　　flying number;

　　in = 0;

　　write_com（0x38）;

　　write_com（0x0c）;

　　write_com（0x06）;

　　write_com（0x01）;

　　write_com（0x80）;

　　for (number=0; number