This document describes a project to build a frequency meter using a microcontroller. It uses an AT89C51 microcontroller and LCD display to measure and directly display the frequency of an input signal. The microcontroller code includes functions for initializing the LCD, sending commands and strings to display readings, and measuring the input signal frequency over one second intervals to update the displayed reading.

1. MICRO CONTROLLER AND MICRO PROCESSER
PROJECT REPORT:
Frequency meter
Submitted to :
Ma’am Maria
Submitted by :
Aroosa
Sheher
Sidra Ali

2. Objective:
Measuring frequency is one of the prime requirements for many applications. The most
obvious method of measuring frequency is using CRO (or now a days using DSO). But
this instrument is not handheld or available with all the students or hobbyists at any
time. It is actually laboratory instrument and not the portable one. Also it is costlier. Also
conventional CRO does not give the direct frequency value read out. One has to first set
the waveform then find time/division and finely calculate time period and frequency. So
it’s a long process that takes time. Another way is use frequency counter that will give
us direct digital readout of frequency. In this no need of first adjusting the waveform into
screen then find time / division and then calculate time period and frequency such as
CRO. Just apply the signal input and get the read out of frequency. That’s why
frequency counters finding their own place in measuring instruments.
Component Details:
AT89C51 Microcontroller:
AT89S51 is an 8-bit microcontroller and belongs to Atmel's 8051 family. AT89S51 has
4KB of Flash programmable and erasable read only memory (PEROM) and 128 bytes of RAM. It
can be erased and program to a maximum of 1000 times.
In 40 pin AT89C51, there are four ports designated as P1, P2, P3 and P0. All these ports are 8-bit
bi-directional ports, i.e., they can be used as both input and output ports. Except P0 which
needs external pull-ups, rest of the ports have internal pull-ups. When 1s are written to these
port pins, they are pulled high by the internal pull-ups and can be used as inputs. These ports
are also bit addressable and so their bits can also be accessed individually.

3. LCD:
LCD (Liquid Crystal Display) screen is an electronic display module and find a wide range of
applications. A 16x2 LCD display is very basic module and is very commonly used in various
devices and circuits.A 16x2 LCD means it can display 16 characters per line and there are 2 such
lines. In this LCD each character is displayed in 5x7 pixel matrix. This LCD has two registers,
namely, Command and Data.
Crystal Oscilator
Implementation on proteus:

4. CODE EXPLANATION:
Our project consist of six functions :
Description of each of the function is given below:
 void delay(unsigned int time)
 void One_Sec_Delay()
 void lcd_initilize()
 void lcd_command(unsigned char cmd)
 void lcd_string(unsigned char str[])
 void lcd_int(unsigned int i)

5. void delay(unsigned int time):
This function will generated delay every time before any byte is sent to LCD
unsigned int i,j;
for(i=0;i<time;i++)
for(j=0;j<255;j++);
void One_Sec_Delay():
This function will calculate number of frequencies per second and set the timers initial
value.from where the timer will start..
TH1 = 0x3C; // for 50 ms delay
TL1 = 0xB0;
void lcd_initilize():
lcd_command(0x38); Function Set: 8-bit, 2 Line, 5x7 Dots
lcd_command(0x0E); Display on Cursor on
lcd_command(0x06); During write operation only shift cursor right (increment cursor)
lcd_command(0x01); Clear Display (also clear DDRAM content)
lcd_command(0x80); it will select top line(first line)
void lcd_command(unsigned char cmd):
function sends command byte to be displayed on LCD.In this command register is selected. and data is
write on the LCD to micro controller. and LCD is enable Now data will start execute
LCD_DATA = cmd;
RS=0;
RW=0;
EN=1;
delay(2);

6. EN=0;
void lcd_string(unsigned char str[]):
for(i=0 ; str[i] ; i++)
LCD_DATA=str[i];
RS=1;
RW=0;
EN=1;
delay(1);
EN=0;
void lcd_int(unsigned int i):
This function takes two arguments. It converts HEX numbers into decimal and then decimal to
ASCII so that they can be displayed on screen .
unsigned char ascii[6];
ascii[5] = 0; // = NULL
ascii[4] = i % 10 | 0x30 ; i = i / 10;
ascii[3] = i % 10 | 0x30 ; i = i / 10;
ascii[2] = i % 10 | 0x30 ; i = i / 10;
ascii[1] = i % 10 | 0x30 ; i = i / 10;
ascii[0] = i % 10 | 0x30 ; i = i / 10;
lcd_string(ascii);