Find the highest and lowest number in array with PIC16F877A

jean12 · Aug 27, 2013

Hello there ,I am design a pressure sensor alarm which uses MPX2100GP interfaced to PIC16F877A;the MPX2100GP is interfaced to an amplifier with TL084 which amplifiers the 1mv generated at 1KPa for getting a good analyzable value;because that sensor MPX2100GP its output is a voltage of some 2.815V and when the pressure is applied on it it changes a little bit, with ccs c compiler I am reading 20 successive numbers in 1minutes and then find the largest and lowest and the difference of the two numbers gives the pressure so that pressure measured can be used to activate the buzzer for example for some limit.

Can you please help me to find the largest and lowest numbers in those 20 digits?

Thanks.

gokul34 · Aug 27, 2013

You can re-arrange the data in your program(by ascending/descending). then you can find the difference from first and last value.

Venkadesh_M · Aug 27, 2013

Do this in your program

Code C - [expand]
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big_value    = 0;
small_value = 0xFFFF;
for ( i = 0; i < 20; i++)
{
if ( array[i] < small_value )
small_value = array[i];
if ( array[i] > big_value )
big_value = array[i];
}

after executing this lines you will have the small and big values....

jean12 · Aug 27, 2013

Hello,the array contains the values from adc module,I am reading the value on AN0 and then they make in array in which I find the highet and lowest ;see here below the codes I was trying to use:

PHP:

#include"16f877a.h"
#device adc=10
#fuses HS,NOWDT,NOLVP,NODEBUG,NOCPD,NOBROWNOUT
#use delay(clock=4M)
#include"lcd.c"


int value,i,k,valuet;
unsigned long value1,valuenew;
//unsigned int value2,value3;
float value3,result;
int array[10];

void main()

{
	set_tris_d(0x00);
	set_tris_a(0xff);
	set_tris_c(0x00);
	set_tris_b(0x00);

	setup_comparator(NC_NC_NC_NC);
   setup_adc(ADC_CLOCK_INTERNAL);
   setup_adc_ports(AN0);
   set_adc_channel(0);
   setup_vref(FALSE);
	lcd_init();
	lcd_gotoxy(1,1);
	while(true)
	{
	delay_us(100);
  
for(i=0;i<10;i++)
{
delay_ms(50);
read_adc(adc_start_only);
delay_us(100);
value=read_adc(adc_read_only);
delay_us(100);
value1=value;
value3=(value1*50)/1023;
delay_us(100);
array[i]=value3;

}
printf(lcd_putc,"\f%d",array[i]);
delay_ms(500);


}
}



for(i=1;i<10;i++)
{
if(array[0]<array[i])
{
//printf(lcd_putc,"\f%f",array[0]);
//delay_ms(500);
printf(lcd_putc,"\fThe result000 is");
delay_ms(1500);
printf(lcd_putc,"\f%f",array[0]);
delay_ms(1500);

jayanth.devarayanadurga · Aug 27, 2013

value3 is float and array[] is int. change array[] to float type.

Code C - [expand]
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float a[10] = {10.2, 55.4, 9.3, 4.6, 234.8, 20.1, 30.5, 40.2, 22.6, 34.1};
 
  float max = a[0];
  float min = a[0];
  usigned int i;
 
 
  for (i = 0; i < 10; i++)
 
    {
 
      if (a[i] > max)
 
        {
 
          max = a[i];
 
        }
 
      else if (a[i] < min)
 
        {
 
          min = a[i];
 
        }
 
    }

jean12 · Aug 31, 2013

No the array is not fixed it has to store the values read by the PIC,so after the PIC reads some 20 values,those 20 will be in one array and then the program has to find the lowest and the highest values among them.

Thanks for the previous response.

jayanth.devarayanadurga · Aug 31, 2013

Use a counter to count no of array elements then in the below code

Code C - [expand]
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for (i = 0; i < 10; i++)

change

Code C - [expand]
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i < 10;

to

Code C - [expand]
1
i < counter;

jean12 · Aug 31, 2013

can you post the complete codes,for reading and comparison?

Thanks

jayanth.devarayanadurga · Aug 31, 2013

Its only possible if your compiler allows to create dynamic array or create an array of 100 elements and then store the adc values to the elements and increment a counter (int variable). After array is loaded with the max adc readings then use the code I posted to get the biggest and smallest values of the array.

kripacharya · Aug 31, 2013

seriously ?

all you have to do is step thru the array and compare 'current <highest/ lowest>' with the next number in the array. D-uh

jean12 · Aug 31, 2013

Can you propose the codes?

Thanks

snishanth512 · Aug 31, 2013

Array length is fixed while program starts executing.

as said by jayanth.devarayanadurga.

you can find the count and start comparing with other values.

you can find the program in any c programming book.

jayanth.devarayanadurga · Aug 31, 2013

Post your code so that it can be modified.

jean12 · Sep 1, 2013

Hello,here are my codes

PHP:

#include"16f877a.h"
#device adc=10
#fuses HS,NOWDT,NOLVP,NODEBUG,NOCPD,NOBROWNOUT
#use delay(clock=4M)
#include"lcd.c"


int value,i,k,valuet;
unsigned long value1,valuenew;
//unsigned int value2,value3;
float value3,result;
int array[10];

void main()

{
    set_tris_d(0x00);
    set_tris_a(0xff);
    set_tris_c(0x00);
    set_tris_b(0x00);

    setup_comparator(NC_NC_NC_NC);
   setup_adc(ADC_CLOCK_INTERNAL);
   setup_adc_ports(AN0);
   set_adc_channel(0);
   setup_vref(FALSE);
    lcd_init();
    lcd_gotoxy(1,1);
    while(true)
    {
    delay_us(100);
  
for(i=0;i<10;i++)
{
delay_ms(50);
read_adc(adc_start_only);
delay_us(100);
value=read_adc(adc_read_only);
delay_us(100);
value1=value;
value3=(value1*50)/1023;
delay_us(100);
array[i]=value3;

}
printf(lcd_putc,"\f%d",array[i]);
delay_ms(500);


}
}



for(i=1;i<10;i++)
{
if(array[0]<array[i])
{
//printf(lcd_putc,"\f%f",array[0]);
//delay_ms(500);
printf(lcd_putc,"\fThe result000 is");
delay_ms(1500);
printf(lcd_putc,"\f%f",array[0]);
delay_ms(1500);

jayanth.devarayanadurga · Sep 1, 2013

Code C - [expand]
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#include"16f877a.h"
#device adc=10
#fuses HS,NOWDT,NOLVP,NODEBUG,NOCPD,NOBROWNOUT
#use delay(clock=4M)
#include"lcd.c"
 
 
int value,i,k,valuet;
unsigned long value1,valuenew;
float value3,result;
int array[25], arraySize = 0;
float min, max;
 
void main()
 
{
        set_tris_d(0x00);
        set_tris_a(0xff);
        set_tris_c(0x00);
        set_tris_b(0x00);
 
        setup_comparator(NC_NC_NC_NC);
    setup_adc(ADC_CLOCK_INTERNAL);
    setup_adc_ports(AN0);
    set_adc_channel(0);
    setup_vref(FALSE);
 
        lcd_init();
        lcd_gotoxy(1,1);
 
        while(true)
        {
            delay_us(100);
  
        for(i = 0; i < 10; i++)
        {
            delay_ms(50);
            read_adc(adc_start_only);
            delay_us(100);
            value=read_adc(adc_read_only);
            delay_us(100);
            value1=value;
            value3=(value1*50)/1023;
            delay_us(100);
            array[i]=value3;
 
            printf(lcd_putc,"\f%d", array[i]);
 
            arraySize++;
 
        }
 
        min  array[0];
        max = array[0];
        
        for (i = 0; i = arraySize; i++) 
            { 
                if (array[i] > max) 
                { 
                    max = array[i];
 
                } 
                else if (array[i] < min) 
                { 
                    min = array[i];
 
                }
 
            }
 
        printf(lcd_putc,"\fThe min is %d", min );
        printf(lcd_putc,"\fThe max is %d", max );
        
        delay_ms(500);
 
 
    }
}

jean12 · Sep 1, 2013

Thanks for your answer I am gonna trying with it,!!
Thx

kripacharya · Sep 1, 2013

jayanth.devarayanadurga said:
...code...

actually there is no need to have a 2nd loop for the search -- it can be included in the 1st loop itself where the values are being acquired by adc

jean12 · Sep 1, 2013

kripacharya said:
actually there is no need to have a 2nd loop for the search -- it can be included in the 1st loop itself where the values are being acquired by adc

So how th codes should look like??

snishanth512 · Sep 1, 2013

Code:

#include"16f877a.h"
#device adc=10
#fuses HS,NOWDT,NOLVP,NODEBUG,NOCPD,NOBROWNOUT
#use delay(clock=4M)
#include"lcd.c"
 
 
int value,i,k,valuet;
unsigned long value1,valuenew;
float value3,result;
int array[25], arraySize = 0;
float min, max;
 
void main()
 
{
        set_tris_d(0x00);
        set_tris_a(0xff);
        set_tris_c(0x00);
        set_tris_b(0x00);
 
        setup_comparator(NC_NC_NC_NC);
    setup_adc(ADC_CLOCK_INTERNAL);
    setup_adc_ports(AN0);
    set_adc_channel(0);
    setup_vref(FALSE);
 
        lcd_init();
        lcd_gotoxy(1,1);
 
        while(true)
        {
            delay_us(100);
        min =0;
        max = 0;

  
        for(i = 0; i < 10; i++)
        {
            delay_ms(50);
            read_adc(adc_start_only);
            delay_us(100);
            value=read_adc(adc_read_only);
            delay_us(100);
            value1=value;
            value3=(value1*50)/1023;
            delay_us(100);
            array[i]=value3;
 
            printf(lcd_putc,"\f%d", array[i]);
 

		if (array[i] > max) 
                { 
                    max = array[i];
 
                } 
                else if (array[i] < min) 
                { 
                    min = array[i];
 
                }
 
        }
 

        printf(lcd_putc,"\fThe min is %d", min );
        printf(lcd_putc,"\fThe max is %d", max );
        
        delay_ms(500);
 
 
    }
}

jean12 · Sep 1, 2013

Here the problem is that,the system is always printing 0 as the minimum number.

Please help

Code C - [expand]
1 2 3 4 5 6 7 8 9	big_value = 0; small_value = 0xFFFF; for ( i = 0; i < 20; i++) { if ( array[i] < small_value ) small_value = array[i]; if ( array[i] > big_value ) big_value = array[i]; }

Find the highest and lowest number in array with PIC16F877A

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