[SOLVED] regarding ldr sensor....

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PRABAKARDEVA

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i had written the adc coding...but i couldn't get the output for ldr sensor.....i couldn't find the flaws in coding....can anyone help?
 

Code: 
int main(void) {
    TRISD = 0x00;

    PORTD = 0x00;
    //adc initialize
    adc_init();
    unsigned int ldr_val;

    while (1) {
        // read channel 0
        ldr_val = adc_read(0);
        ldr_val /= 10;
         if (ldr_val > 50)
            PORTD = 0xFF;
        else
            PORTD = 0x00;
    }
    return (1);
}
 

hi

i am not familiar in pic. but generally, i will give some points, i hope you had correct initialization in adc code and no hard ware faults. first thing is, check the ref voltage of the micro-controller ,
second thing is, check the datatype of the ldr_val
 



what is fault in datatype?
 

hi

i didnt see the data type of the ldr_val before, now i saw that , i thing , the output of the ADC in pic 10 bits resolution. so unsigned int is enough.
 

TRISx is not set for ADC pin. ANSEx, ADCONx, CMCON, CM1CON0, CM2CON0, VRCON, CVRCON, registers if exists is not configured. LDR circuit o/p voltage range is not mentioned. uC and Fosc is not mentioned. Post Circuit and mikroC project files zipped.
 

jayanth.devarayanadurga said:
TRISx is not set for ADC pin. ANSEx, ADCONx, CMCON, CM1CON0, CM2CON0, VRCON, CVRCON, registers if exists is not configured. LDR circuit o/p voltage range is not mentioned. uC and Fosc is not mentioned. Post Circuit and mikroC project files zipped.
Click to expand...
hi jayanth.....i had just posted my main file.....i had written driver file for the adc_init() which done the everything.fosc and uc mentioned in compiler.....posted that code for your verification.
 

HTML: 
void adc_init(void)
{
	ADRESH=0;
	ADRESL=0;
	RA0=0;
	TRISA0=1;
	ADCON0=0x81;
	ADCON1=0xCE;
	}
	int adc_read(unsigned char channel)
	{
		unsigned char lsb,msb;
		unsigned char result;
	ADCON0 &= ~(0x07 << 3);         
    ADCON0 |= (channel<< 3);
    __delay_ms(1);
    ADON=1;
		GO_DONE=1;
		while(GO_DONE)
		{
			;
			}
			lsb=ADRESL;
			msb=ADRESH;
			result=(msb>>8)+lsb;
			return result;
			}



may i change need to change anything?
 

I hope msb and lsb are 8 bit variables, result is 16 bit variable and left justified is used for ADC result. So, use

Code C - [expand]
1

result = (msb << 8) + lsb;


or

Code C - [expand]
1

result = (msb << 8) | lsb;


ADCON0 value is wrong. Mention Fosc used and show how you calculated Tad.
 
Last edited:

i had tried that justification..but i couldn't get the output.....actually i was trying to see the result of the adc by using lcd.....i got the output '24'.i don't know..how i got?
 

Circuit is ok. You need resistors for LEDs in real circuit. Calculate Tad for 20 MHz and set ADCS0-ADCS2 accordingly.

Remove these

Code C - [expand]
1
2

ADCON0 &= ~(0x07 << 3);         
ADCON0 |= (channel<< 3);


Use these values

Code C - [expand]
1
2

ADCON0=0x81;
ADCON1=0x8E;
 
Last edited:

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