4-Wire Resistive Touch Screen Interfacing with PIC Micro-Controller

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Hello! Everyone

I am using this touch screen driver circuit

https://researchdesignlab.com/4-wire-resistive-touch-screen-driver.html

It works fine, and i am getting adc values in the range 100(minimum) - 700(maximum) for both axis.
Is this the normal, as i was expecting 0-1023 adc values.

The program i am using as follow:

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Code C - [expand]
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#include <stdint.h>
#include <stdio.h>
 
// Glcd module connections
char GLCD_DataPort at PORTD;
 
sbit GLCD_CS1 at RB1_bit;
sbit GLCD_CS2 at RB0_bit;
sbit GLCD_RS  at RC1_bit;
sbit GLCD_RW  at RC0_bit;
sbit GLCD_EN  at RC2_bit;
sbit GLCD_RST at RB5_bit;
 
sbit GLCD_CS1_Direction at TRISB1_bit;
sbit GLCD_CS2_Direction at TRISB0_bit;
sbit GLCD_RS_Direction  at TRISC1_bit;
sbit GLCD_RW_Direction  at TRISC0_bit;
sbit GLCD_EN_Direction  at TRISC2_bit;
sbit GLCD_RST_Direction at TRISB5_bit;
// End Glcd module connections
 
// Touch Panel module connections
sbit DriveA at RB2_bit;
sbit DriveB at RB3_bit;
sbit DriveA_Direction at TRISB2_bit;
sbit DriveB_Direction at TRISB3_bit;
// End Touch Panel module connections
 
 
char glcd_data[16] = {0};
 
uint16_t Get_X( void );
uint16_t Get_Y( void );
 
void main()
{
  static uint16_t x_pos_prev, y_pos_prev = 0;
  TRISB2_bit = 0;
  TRISB3_bit = 0;
  RB2_bit = 0;
  RB3_bit = 0;
  Glcd_Init();
  Delay_ms(100);
  // Initialize ADC
  //////////////////////////////////////////////////////////////////////////////
  ADCON0.ADON = 1;
  // Set Reference Voltage
  ADCON1.VCFG1  = 0;    // Vss
  ADCON1.VCFG0  = 0;    // Vdd
  // Configure ADC Channels
  TRISA |= 0x1F;  // AN0-AN4 as Input Pins
  // Channel 0-6 as Analog Channels
  ADCON1.PCFG0 = 0;
  ADCON1.PCFG1 = 0;
  ADCON1.PCFG2 = 0;
  ADCON1.PCFG3 = 1;
  // Clock Configuration
  ADCON2.ADFM   = 1;    // Right Justified
  // Acquisition Time 2TAD
  ADCON2.ACQT0 = 1;
  ADCON2.ACQT1 = 0;
  ADCON2.ACQT2 = 0;
  // Clock Source FOSC/64
  ADCON2.ADCS0 = 0;
  ADCON2.ADCS1 = 1;
  ADCON2.ADCS2 = 1;
  //////////////////////////////////////////////////////////////////////////////
  Glcd_Fill(0);
  Delay_ms(1000);
  Glcd_Fill(0xFF);
  Delay_ms(1000);
  Glcd_Fill(0);
  Glcd_Write_Text("Touch Screen",0,0,1);
  TP_Init(128,64,0,1);
  TP_Set_ADC_Threshold(700);
 
  while(1)
  {
    /*
    uint16_t x_pos, y_pos;
    x_pos = Get_X();
    y_pos = Get_Y();
    if( x_pos > 100 && x_pos < 700 && y_pos > 100 && y_pos < 700 )
    {
      uint32_t temp1, temp2;
      temp1 = x_pos - 100;
      temp1 = temp1*128/600;
      temp2 = y_pos - 100;
      temp2 = temp2*64/600;
      sprintf(glcd_data,"%.4d    %.4d    ",x_pos,y_pos);
      Glcd_Write_Text(glcd_data,0,0,1);
      Glcd_Dot((uint8_t)temp1,(uint8_t)temp2,1);
      //Delay_ms(100);
    }
    */
    uint16_t adc_value = 0;
    adc_value = Adc_Read(4);
    sprintf(glcd_data,"Adc Value = %.4d",adc_value);
    Glcd_Write_Text(glcd_data,0,1,1);
 
    adc_value = Get_X();
    if( (abs(adc_value - x_pos_prev) > 10) && adc_value )
    {
      sprintf(glcd_data,"X Value = %.4d",adc_value);
      Glcd_Write_Text(glcd_data,0,2,1);
      x_pos_prev = adc_value;
    }
 
    adc_value = Get_Y();
    if( (abs(adc_value - y_pos_prev) > 10) && adc_value )
    {
      sprintf(glcd_data,"Y Value = %.4d",adc_value);
      Glcd_Write_Text(glcd_data,0,3,1);
      y_pos_prev = adc_value;
    }
    Delay_ms(10);
  }
}
 
uint16_t Get_X( void )
{
  uint16_t x_cor = 0;
  RB2_bit = 1;
  RB3_bit = 0;
  Delay_ms(5);
  x_cor = Adc_Read(0);
}
uint16_t Get_Y( void )
{
  uint16_t y_cor = 0;
  RB3_bit = 1;
  RB2_bit = 0;
  Delay_ms(5);
  y_cor = Adc_Read(1);
}

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I want that my program draw using whatever i draw using fingers on the glcd using touch screen.
For that i used this code, but it fails, it just displaying some random dots.

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Code C - [expand]
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uint16_t x_pos, y_pos;
    x_pos = Get_X();
    y_pos = Get_Y();
    if( x_pos > 100 && x_pos < 700 && y_pos > 100 && y_pos < 700 )
    {
      uint32_t temp1, temp2;
      temp1 = x_pos - 100;
      temp1 = temp1*128/600;
      temp2 = y_pos - 100;
      temp2 = temp2*64/600;
      sprintf(glcd_data,"%.4d    %.4d    ",x_pos,y_pos);
      Glcd_Write_Text(glcd_data,0,0,1);
      Glcd_Dot((uint8_t)temp1,(uint8_t)temp2,1);
      
    }

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