INTERFACING MICROCONTROLLER WITH | INTERFACING PERIPHERALS

Interfacing a microcontroller with a PC using serial port

Interfacing a microcontroller with a PC using serial port

NOTE: Safety is your responsibility. While the information contained in these pages is intended to instruct in a meaningful and safe manor, the construction of any project often comes with a certain level of inherent danger. As a result, the author in no way assumes any responsibility for any damages incurred while following the steps or instructions in these pages including but not limited to property and personal injury/damage/loss of any kind.  As always, please use proper safety gear when using any power tools or undertaking any construction project, AND USE COMMON SENSE!

This circuit provides an interface between a standard inverted logic +/-12V RS-232 device (e.x. a PC) and a non-inverted 0-5 volt device (e.x. a microcontroller). The circuit does not require a separate external power supply since it "steels" power from the RS-232 DTR and RTS pins. This circuit supports full bidirectional receive and transmit signals. 

Many dedicated IC's already exist which are specifically designed to perform this task and which require the addition of just a few external components (the most popular of which are made by Maxim Integrated Products).  The intention of designing this circuit was not to outperform these IC's, but rather to design a simple bi-directional RS-232 compatible interface which does not require an external power supply and can be produced quickly with off-the-shelf parts (which are available from Radio-Shack).  

The completed and fully functional circuit is depicted in Figure 1.  The design is fairly elegant in its simplicity while still including a number of features to virtually eliminate the possibility of harming any of the connected electronic devices**. 

Figure 1: Bi-directional serial port interface circuit (Rx & Tx).

The PCB layout for this design is depicted in Figure 2.  This layout is in no way optimized and can probably be significantly reduced in size if you move things around a bit.  Nevertheless. the resulting PCB is about 1 inch square and was sufficiently small for my application at the time.

Figure 2: PCB layout and connection descriptions for the serial port interface.

The schematic for the circuit described in this page is depicted below.

Figure 3: Schematic diagram for the serial port interface (Rx & Tx).



**Disclaimer: While the circuit was engineered to minimize the possibility of harming any of the connected electronic devices, the author makes to claims or warranties to the safety of this electronic circuit and in no way assumes any responsibility for any damages incurred while building or using the device described in these pages including but not limited to property and personal injury/damage/loss of any kind.  Golden rule: always be sure to test your circuits before connecting them to anything of value!

LCD based voting machine using 8051 microcontroller (AT89C51)

Electronic voting machine has now replaced the traditional mechanism of voting due to several advantages like security, automatic counting etc. This project presents a way to develop an electronic voting machine which displays the count of votes on a 16x2 LCD interface. A user can get his/her vote register through a set of switches (one for each candidate). After every cast of vote, the subsequent count can be seen on LCD. The circuit uses AT89C51 microcontroller and the code for the project has been written in C.

DESCRIBTION(click here)

• 
  
  
  
  
  This LCD based electronic voting machine is designed for four candidates. The input part consists of a set of six tactile switches. The switches and 16x2 LCD are interfaced to microcontroller AT89C51 for various operations and displays.
  The provision of casting votes for the candidates has been provided through four of these switches. These switches are made active high and connected to pins 2-5 (P1^1 – P1^4) of the controller. The remaining two switches (both active low) are to start and stop the voting procedure. They are connected to pins 1 and 6 (P1^0 and P1^5) respectively. The Init (start) switch initializes the voting system when pressed, while the Stop switch ends the voting and displays the poll results on LCD screen.
  For more details on working with LCD, refer LCD interfacing with 8051. The data pins of the LCD (pins 7-14) are connected to the output port P2 of the microcontroller. The control pins (RS, R/W and EN) are connected to port P3 pins P3^0, P3^1 & P3^6 respectively.
  Working:
  The voting is started by pressing the Init switch after which the user is prompted to vote. The count of votes is stored in four different variables. As soon as the user votes for a candidate by pressing one of the switches, the value of the corresponding variable is increased by one. After this a Thank you message is displayed on LCD to acknowledge the registration of user’s vote.
  The message stays on the screen until the next user either presses the Init button to cast another vote or Stop switch is pressed get the poll results. When the stop button is pressed, the names of the candidates are displayed along with their vote counts. After some delay, the result is displayed which could be either declaration of the winner candidate or the candidates with a clash of their number of votes.

CIRCUIT DIAGRAM(click here)

VIDEO(click here)

CODE(click here)

• 
  // Program to make a voting machine using LCD
  
  
  
  #include<reg51.h>
  
  #define msec 50
  
  #define lcd_data_str_pin P2 
  
  sbit rs = P3^0;  //Register select (RS) pin
  
  sbit rw = P3^1;  //Read write(RW) pin
  
  sbit en = P3^6;  //Enable(EN) pin
  
  sbit ini_pin = P1^0; // Start voting pin
  
  sbit stop_pin = P1^5; // Stop voting pin
  
  
  
  sbit candidate_1=P1^1;  //Candidate1
  
  sbit candidate_2=P1^2;  //Candidate2
  
  sbit candidate_3=P1^3;  //Candidate3
  
  sbit candidate_4=P1^4;  //Candidate4
  
  int max = 0;
  
  int carry = 0;
  
  int arr[4];
  
  
  
  int vote_amt[3],j;
  
  unsigned int vote_1,vote_2,vote_3,vote_4;
  
  
  
  void delay(int delay_time)  // Time delay function
  
  {
  
  int j,k;
  
  for(j=0;j<=delay_time;j++)
  
    for(k=0;k<=1000;k++);
  
  }
  
  
  
  void lcd_cmd(unsigned char cmd_addr)  //Function to send command to LCD
  
  {
  
  lcd_data_str_pin = cmd_addr;
  
  en = 1;
  
  rs = 0;
  
  rw = 0;
  
  delay(1);
  
  en = 0;
  
  return;
  
  }
  
  
  
  void lcd_data_str(char str[50])  //Function to send string
  
  { 
  
  int p;
  
  for (p=0;str[p]!='\0';p++)
  
  {
  
    lcd_data_str_pin = str[p];
  
    rw = 0;
  
    rs = 1;
  
    en = 1;
  
    delay(1);
  
    en = 0;
  
  }
  
  return;
  
  }
  
  
  
  void lcd_data_int(unsigned int vote)  //Function to send 0-9 character values
  
  { 
  
  char dig_ctrl_var;
  
  int p;
  
  for (j=2;j>=0;j--)
  
  {
  
    vote_amt[j]=vote%10;
  
    vote=vote/10;
  
  }
  
  
  
  for (p=0;p<=2;p++)
  
  {
  
    dig_ctrl_var = vote_amt[p]+48;
  
    lcd_data_str_pin = dig_ctrl_var;
  
    rw = 0;
  
    rs = 1;
  
    en = 1;
  
    delay(1);
  
    en = 0;
  
  }
  
  return;
  
  } 
  
  
  
  void vote_count()  // Function to count votes
  
  {
  
  while (candidate_1==0 && candidate_2==0 && candidate_3==0 && candidate_4==0);
  
  if (candidate_1==1)
  
  {
  
    while (candidate_1 == 1);
  
     {
  
      vote_1 = vote_1 + 1;
  
     }
  
  }
  
  
  
  if (candidate_2==1)
  
  {
  
    while (candidate_2 == 1);
  
     {
  
      vote_2 = vote_2 + 1;
  
     }
  
  }
  
  
  
  if (candidate_3==1)
  
  {
  
    while (candidate_3 == 1);
  
     {
  
      vote_3 = vote_3 + 1;
  
     }
  
  }
  
  
  
  if (candidate_4==1)
  
  {
  
    while (candidate_4 == 1);
  
     {
  
      vote_4 = vote_4 + 1;
  
     }
  
  }
  
  }
  
  
  
  void lcd_ini()
  
  {
  
      lcd_cmd(0x38);
  
  delay(msec);
  
  lcd_cmd(0x0E);
  
  delay(msec);
  
  lcd_cmd(0x01);
  
  delay(msec);
  
  lcd_cmd(0x81);
  
  delay(msec);
  
  lcd_data_str("Welcome!!!");
  
  delay(100);
  
  lcd_cmd(0x01);
  
  delay(msec);
  
  lcd_cmd(0x80);
  
  delay(msec);
  
  lcd_data_str( "Press" );
  
  delay(msec);
  
  lcd_cmd(0x14);
  
  delay(msec);
  
  lcd_data_str("button");
  
  delay(msec);
  
  
  
  delay(msec);
  
  lcd_cmd(0xC0);
  
  delay(msec);
  
  lcd_data_str("to");
  
  delay(msec);
  
  lcd_cmd(0x14);
  
  delay(msec);
  
  lcd_data_str("vote");
  
  delay(100);
  
  lcd_cmd(0x01);
  
  delay(msec);
  
  lcd_cmd(0x80);
  
  delay(msec);
  
  lcd_data_str("P1");
  
  delay(msec);
  
  lcd_cmd(0x84);
  
  delay(msec);
  
  lcd_data_str("P2");
  
  delay(msec);
  
  lcd_cmd(0x88);
  
  delay(msec);
  
  lcd_data_str("P3");
  
  delay(msec);
  
  lcd_cmd(0x8C);
  
  delay(msec);
  
  lcd_data_str("P4");
  
  delay(msec);
  
  
  
  vote_count();
  
  lcd_cmd(0x01);
  
  delay(msec);
  
  lcd_cmd(0x85);
  
  delay(msec);
  
  lcd_data_str("Thank");
  
  delay(msec);
  
  lcd_cmd(0x14);
  
  delay(msec);
  
  lcd_data_str("You!!");
  
  delay(100);
  
  }
  
  
  
  void results()  // Function to show results
  
  {
  
  int i;
  
  carry = 0;
  
  lcd_cmd(0x01);
  
  delay(msec);
  
  lcd_cmd(0x80);
  
  delay(msec);
  
  lcd_data_str("Results");
  
  delay(msec);
  
  lcd_cmd(0x14);
  
  delay(msec);
  
  lcd_data_str("Are");
  
  delay(msec);
  
  lcd_cmd(0x14);
  
  delay(msec);
  
  lcd_data_str("Out");
  
  delay(msec);
  
  
  
    lcd_cmd(0x01);
  
  delay(msec);
  
  lcd_cmd(0x80);
  
  delay(msec);
  
  lcd_data_str("P1");
  
  delay(msec);
  
  lcd_cmd(0x84);
  
  delay(msec);
  
  lcd_data_str("P2");
  
  delay(msec);
  
  lcd_cmd(0x88);
  
  delay(msec);
  
  lcd_data_str("P3");
  
  delay(msec);
  
  lcd_cmd(0x8C);
  
  delay(msec);
  
  lcd_data_str("P4");
  
  delay(msec);
  
  
  
  lcd_cmd(0xC0);
  
  delay(100);
  
  lcd_data_int(vote_1);
  
  delay(msec);
  
  
  
  lcd_cmd(0xC4);
  
  delay(msec);
  
  lcd_data_int(vote_2);
  
  delay(msec);
  
  
  
  lcd_cmd(0xC8);
  
  delay(msec);
  
  lcd_data_int(vote_3);
  
  delay(msec);
  
  
  
  lcd_cmd(0xCC);
  
  delay(msec);
  
  lcd_data_int(vote_4);
  
  delay(300);
  
  
  
  arr[0] = vote_1;
  
  arr[1] = vote_2;
  
  arr[2] = vote_3;
  
  arr[3] = vote_4;
  
  
  
  for( i=0; i<4; i++)
  
  {
  
    if(arr[i]>=max)
  
    max = arr[i];
  
  }
  
  
  
  if ( (vote_1 == max) && ( vote_2 != max) && (vote_3 != max)&& (vote_4 != max) )
  
  {
  
    carry = 1;
  
    lcd_cmd(0x01);
  
    delay(msec);
  
    lcd_cmd(0x82);
  
    delay(msec);
  
    lcd_data_str("Hurray!!!");
  
    delay(50);
  
    lcd_cmd(0xC4);
  
    delay(msec);
  
    lcd_data_str("P1");
  
    delay(msec);
  
    lcd_cmd(0x14);
  
    delay(msec);
  
    lcd_data_str("wins");
  
    delay(msec);
  
  }
  
  
  
  if ( (vote_2 == max) && ( vote_1 != max) && (vote_3 != max)&& (vote_4 != max) )
  
  {
  
    carry = 1;
  
    lcd_cmd(0x01);
  
    delay(msec);
  
    lcd_cmd(0x82);
  
    delay(msec);
  
    lcd_data_str("Hurray!!!");
  
    delay(50);
  
    lcd_cmd(0xC4);
  
    delay(msec);
  
    lcd_data_str("P2");
  
    delay(msec);
  
    lcd_cmd(0x14);
  
    delay(msec);
  
    lcd_data_str("wins");
  
    delay(msec);
  
  }
  
  
  
  if ( (vote_3 == max) && ( vote_2 != max) && (vote_1 != max)&& (vote_4 != max) )
  
  {
  
    carry = 1;
  
    lcd_cmd(0x01);
  
    delay(msec);
  
    lcd_cmd(0x82);
  
    delay(msec);
  
    lcd_data_str("Hurray!!!");
  
    delay(50);
  
    lcd_cmd(0xC4);
  
    delay(msec);
  
    lcd_data_str("P3");
  
    delay(msec);
  
    lcd_cmd(0x14);
  
    delay(msec);
  
    lcd_data_str("wins");
  
    delay(msec);
  
  }
  
  
  
  if ( (vote_4 == max) && ( vote_2 != max) && (vote_3 != max)&& (vote_1 != max) )
  
  {
  
    carry = 1;
  
    lcd_cmd(0x01);
  
    delay(msec);
  
    lcd_cmd(0x82);
  
    delay(msec);
  
    lcd_data_str("Hurray!!!");
  
    delay(50);
  
    lcd_cmd(0xC4);
  
    delay(msec);
  
    lcd_data_str("P4");
  
    delay(msec);
  
    lcd_cmd(0x14);
  
    delay(msec);
  
    lcd_data_str("wins");
  
    delay(msec);
  
  }
  
  
  
  if (carry==0)
  
  {
  
    lcd_cmd(0x01);
  
    delay(msec);
  
    lcd_cmd(0x82);
  
    delay(msec);
  
    lcd_data_str("clash");
  
    delay(50);
  
    lcd_cmd(0x14);
  
    delay(msec);
  
    lcd_data_str("between!!!");
  
    delay(50);
  
    if(vote_2 == max)
  
    {
  
     lcd_cmd(0xC5);
  
     lcd_data_str("P2");
  
     delay(50);
  
    }
  
    if(vote_3 == max)
  
    {
  
     lcd_cmd(0xC9);
  
     lcd_data_str("P3");
  
     delay(50);
  
    }
  
    if(vote_4 == max)
  
    {
  
     lcd_cmd(0xCD);
  
     lcd_data_str("P4");
  
     delay(50);
  
    }
  
  }
  
  }
  
  
  
  void main()
  
  {
  
  ini_pin = stop_pin = 1;
  
  vote_1 = vote_2 = vote_3 = vote_4 = 0;
  
  candidate_1 = candidate_2 = candidate_3 = candidate_4 = 0;
  
  lcd_cmd(0x38);
  
  delay(msec);
  
  lcd_cmd(0x0E);
  
  delay(msec);
  
  lcd_cmd(0x01);
  
  delay(msec);
  
  lcd_cmd(0x80);
  
  delay(msec);
  
  lcd_data_str( "Press" );
  
  delay(msec);
  
  lcd_cmd(0x14);
  
  delay(msec);
  
  lcd_data_str("init");
  
  delay(msec);
  
  
  
  delay(msec);
  
  lcd_cmd(0xC0);
  
  delay(msec);
  
  lcd_data_str("to");
  
  delay(msec);
  
  lcd_cmd(0x14);
  
  delay(msec);
  
  lcd_data_str("begin");
  
  delay(100);
  
  while(1)
  
  {
  
    while(ini_pin != 0)
  
    {
  
     if (stop_pin == 0)
  
     break;
  
    }
  
    if (stop_pin == 0)
  
    {
  
    break;
  
    }
  
    lcd_ini();
  
  }
  
  
  
  while(1)
  
  {
  
  results();
  
  }
  
  }
  
  

COMPONENTS(click here)

• AT89C51 Microcontroller
• Preset
• LCD

Distance measurement using InfraRed sensor with ADC0804 & 8051 microcontroller (AT89C51)

Infrared sensors find numerous applications in electronic systems. Commonly used as obstacle detector, their output is used in digital form (high & low logic) by employing a comparator.  This topic explains a way to use the sensor’s output in its original analog form. Thus, along with detecting an obstacle, its exact distance can also be obtained. This is achieved by processing the output of IR sensor through an ADC0804 (analog to digital converter). The ADC is calibrated to get almost accurate distance measurement.

The measured distance is also displayed on an LCD screen. The ADC0804 and LCD are interfaced with 8051 microcontroller (AT89C51) to perform these operations. The major drawback of IR based sensors is their capability of detecting short distances.

DESCRIBTION:

• This project mainly consists of three units: a sensor unit, an ADC component and the LCD module.
  
  The IR receiver detects the IR radiations transmitted by an IR LED. The output voltage level of this IR sensor depends upon the intensity of IR rays received by the receiver. The intensity, in turn, depends on the distance between the sensor module and the obstacle. When the distance between IR pair and obstacle is lesser, more IR radiations fall on the receiver, and vice versa. The receiver along with a resistor forms a voltage divider whose output is supplied as the input for ADC0804.
  
  

CIRCUIT DIAGRAM:

• 

CODE:

• 
  //Program to interface IR sensor using ADC 0804. Set Vref =1.5v for ADC 0804
  
  
  
  #include<reg51.h>
  
  #define port P3
  
  #define adc_input P1
  
  #define dataport P0
  
  #define sec 100
  
  sbit rs = port^0;
  
  sbit rw = port^1;
  
  sbit e = port^2;
  
  
  
  sbit wr= port^3;
  
  sbit rd= port^4;
  
  sbit intr= port^5;
  
  
  
  int test_final=0 ,shift=0;
  
  
  
  void delay(unsigned int msec ) // Time delay function
  
  {
  
  int i ,j ;
  
  for(i=0;i<msec;i++)
  
    for(j=0; j<1275; j++);
  
  }
  
  
  
  void lcd_cmd(unsigned char item) // Function to send command to LCD
  
  {
  
  dataport = item;
  
  rs= 0;
  
  rw=0;
  
  e=1;
  
  delay(1);
  
  e=0;
  
  return;
  
  }
  
  
  
  void lcd_data(unsigned char item)  // Function to send data to LCD
  
  {
  
  dataport = item;
  
  rs= 1;
  
  rw=0;
  
  e=1;
  
  delay(1);
  
  e=0;
  
  return;
  
  }
  
  
  
  void lcd_data_string(unsigned char *str) // Function to send string to LCD
  
  {
  
  int i=0;
  
  while(str[i]!='\0')
  
  {
  
    lcd_data(str[i]);
  
    i++;
  
    delay(1);
  
  }
  
  return;
  
  }
  
  
  
  void convert()
  
  {
  
  int s;
  
  lcd_cmd(0x81);
  
  delay(2);
  
  lcd_data_string("output:");
  
  s=test_final/100;
  
  test_final=test_final%100;
  
  lcd_cmd(0x8a);
  
  if(s!=0)
  
  lcd_data(s+48);
  
  else
  
  lcd_cmd(0x06);
  
  s=test_final/10;
  
  test_final=test_final%10;
  
  lcd_data(s+48);
  
  lcd_data(test_final+48);
  
  lcd_data(' ');
  
  if(shift>16)
  
  {
  
  lcd_cmd(0xc0+(shift-1));
  
  lcd_data_string("       ");
  
  shift=0; 
  
  }
  
  lcd_cmd(0xc0+(shift-1));
  
  lcd_data(' ');
  
  lcd_cmd(0xc0+shift);
  
  lcd_data_string("CALIBRATE IT");
  
  delay(30);
  
  }
  
  
  
  void main()
  
  {
  
  adc_input=0xff;
  
  lcd_cmd(0x38);  //2 Line, 5X7 Matrix
  
  lcd_cmd(0x0c);  //Display On, Cursor Blink
  
  delay(2);
  
  lcd_cmd(0x01);  // Clear Screen
  
  delay(2);
  
  lcd_cmd(0x81);  // Setting cursor to first position of first line
  
  delay(2);
  
  while(1)
  
  {
  
    shift++;
  
    delay(1);
  
    rd=1;
  
    wr=0;
  
    delay(1);
  
    wr=1;
  
    while(intr==1);
  
    rd=0;
  
    test_final=adc_input;
  
    delay(1);
  
    intr=1;
  
    convert();
  
  }
  
  }
  
  

COMPONENTS:

• IR LED | Infrared LED
• AT89C51 Microcontroller
• Preset
• ADC0804
• LCD