Help with PIC16F716 ADC code using MPLAB v8.88

richardlaishram · Oct 15, 2013

I'm using the header file <htc.h> for my PIC16F716 ADC project using PIC16
Following are the codes after referring the datasheet and a sample code for PIC16F877A.

Code:

void InitADC(void)
{
	TRISA0 = 0x01;			// PortA Pin0 configured as input
	ADCON1 = 0x00;			// PortA configured as Analog input with Vref as Vdd
	ADCON0 = 0x41;			// ADC Enabled
}

unsigned int ADCValue0(void)
{
	ADCON0 &= 0x45;			// Start AD Conversion
	ADCON0 |= 0x40;			// Conversion Cycle in Progress
	__delay_ms(10);
	while(ADCON0 |= 0x40);	// Wait for AD conversion to Complete
	return ADRES;			// ADC result stored
}

when building the project, I'm getting the error undefined identifier "ADRES"

I've got a code with PIC16F877A for an ADC Project, I've tried it and it's working fine in Proteus.

Code:

void InitADC(void)
{
	ADCON1 = 0x80;
	TRISA = 0x2F;
	ADCON0 = 0x81;
}

unsigned int ADCValue(void)
{
	ADCON0 &= 0x87;
	ADCON0 |= 0x08;
        __delay_ms(10);
	GO_nDONE  = 1;
	while(GO_nDONE);
	return ((ADRESH<<8)+ADRESL);
}

Here's my query:
1. The ADC result registers for PIC16F877A (ADRESH and ADRESL - 10bit) is not showing any error whereas PIC16F716 (ADRES - 8bit) is not recognized by <htc.h>
2. Can I use GO_nDONE to check for the completion of AD Conversion in PIC16F716 also?

Thanks in Advance.

arunbharathi.arasu · Oct 15, 2013

Try this..... It may help you.....

Code:

void InitADC(void)
{
	TRISA0 = 0x01;			
	ADCON1 = 0x00;			
	ADCON0 = 0x41;			
}

unsigned int ADCValue0(void)
{
	ADCON0 &= 0x45;			
	ADCON0 |= 0x40;
GO_nDONE  = 1;			//changes
	__delay_ms(10);
	while(ADCON0 |= 0x40);	

	return(ADRES);               //changes			
}

richardlaishram · Oct 15, 2013

Even this is not working. I tried using the ADRESH register and it's working fine with Proteus.

Code:

unsigned int ADCValue(void)
{
	ADCON0 &= 0x45;
	ADCON0 |= 0x40;
        __delay_ms(10);
	GO_nDONE  = 1;
	while(GO_nDONE);
	return ADRESH;
}

I need to check it again with the actual hardware, though. I'm not able to find any register with the name ADRES in the Compiler Help pdf also, so I guessed and tried ADRESH, and luckily it worked in Proteus.

mathespbe · Oct 15, 2013

1. ADRES is not a reg of PIC16F877A. Instead you have ADRESH and ADRESL regs... It's just used for 10 bit resolution... But PIC16F716 has only 8 bit resolution....
2. GO_nDONE is similar for both...

- - - Updated - - -

richardlaishram said:
Even this is not working. I tried using the ADRESH register and it's working fine with Proteus.

Code:

unsigned int ADCValue(void) { ADCON0 &= 0x45; ADCON0 |= 0x40; __delay_ms(10); GO_nDONE = 1; while(GO_nDONE); return ADRESH; }

I need to check it again with the actual hardware, though. I'm not able to find any register with the name ADRES in the Compiler Help pdf also, so I guessed and tried ADRESH, and luckily it worked in Proteus.

ADRESL is Lower 8 bits and ADRESH contains higher 2 bits of your result. You need to use both the regs to get proper result...

jayanth.devarayanadurga · Oct 15, 2013

Zip and post complete project files.

richardlaishram · Oct 16, 2013

Created a whole new PIC16F716 project in MPLAB v8.8 again and now the previous code is working fine with ADRES register. Thanks for your help. Maybe I have selected the wrong chip and parameters.

richardlaishram · Oct 28, 2013

jayanth.devarayanadurga said:
Zip and post complete project files.

These whole time I ignored the ADC since it was working totally fine with Proteus, finally when I flashed the code, it's not working. Can you please help
View attachment PIC16F716_ADC.rar

Venkadesh_M · Oct 28, 2013

what is happening in hardware can you post the schematic??

jayanth.devarayanadurga · Oct 28, 2013

I think you used code of some other PIC with the PIC you are using. If that is right then ADCONx values change. Read the datasheet.

If 4 MHz clock then

Code C - [expand]
1
__CONFIG(FOSC_XT & WDTE_ON & PWRTE_ON & CP_OFF & BOREN_OFF);

richardlaishram · Oct 28, 2013

Venkadesh_M said:
what is happening in hardware can you post the schematic??

I don't have the schematics for now. For the ADC I/P I'm using a voltage divider from a 12V battery. For the 5V Power supply I'm using a 7805 voltage regulator . The problem is that the ADC O/P value is jumbling and not showing the accurate value.

Now I tried connecting the power supply to a 12V battery and seems like the ADC value is showing the correct value. Can the problem be because of the 12V AC-DC adapter used for powering the board?

- - - Updated - - -

jayanth.devarayanadurga said:
I think you used code of some other PIC with the PIC you are using. If that is right then ADCONx values change. Read the datasheet.

I have gone through the datasheets, sir.
ADCON1 = 0x00; // All pins as ADC
ADCON0 = 0x41; // ADC ON and Fosc/8
ADCON0 &= 0x4D; // ADC ON, Conversion in Progress, AN1 Selected and Fosc/8
ADCON0 |= 0x08; // ANI Selection

Correct me if I'm wrong in this. Checking with the config now. Thanks

Venkadesh_M · Oct 28, 2013

richardlaishram said:
Now I tried connecting the power supply to a 12V battery and seems like the ADC value is showing the correct value. Can the problem be because of the 12V AC-DC adapter used for powering the board?

Exactly.. The Source and uc shd have a common ground and the value to be measured is shd be stable unless no use in software corrections.......

jayanth.devarayanadurga · Oct 28, 2013

Maybe your AC-DC power adapter doesn't have good filtering.

richardlaishram · Oct 28, 2013

Venkadesh_M said:
Exactly.. The Source and uc shd have a common ground and the value to be measured is shd be stable unless no use in software corrections.......

jayanth.devarayanadurga said:
Maybe your AC-DC power adapter doesn't have good filtering.

Thanks for your replies. Sorry to bother you again. Now I'm trying to use 2 ADC Channels. I have gone through lots of example codes. Can you please help where have I gone wrong in this code. Thanks in advance.

jayanth.devarayanadurga · Oct 28, 2013

Code C - [expand]
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__delay_ms(250);
        adcval2 = ADC_Chan0();
        o = adcval2%10;
        n = (adcval2%100)/10;
        m = adcval2/100;
        __delay_ms(250);
        WriteCommandToLCD(0xC5);
        WriteDataToLCD(o+0x30);
        WriteDataToLCD(n+0x30);
        WriteDataToLCD(m+0x30);

richardlaishram · Oct 28, 2013

jayanth.devarayanadurga said:

Code C - [expand]
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__delay_ms(250);
        adcval2 = ADC_Chan0();
        o = adcval2%10;
        n = (adcval2%100)/10;
        m = adcval2/100;
        __delay_ms(250);
        WriteCommandToLCD(0xC5);
        WriteDataToLCD(o+0x30);
        WriteDataToLCD(n+0x30);
        WriteDataToLCD(m+0x30);

Here I'm trying to display the exact 8-bit ADC value (0-255). Please tell me if I have made any mistake.

Help with PIC16F716 ADC code using MPLAB v8.88

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Code C - [expand]
1	__CONFIG(FOSC_XT & WDTE_ON & PWRTE_ON & CP_OFF & BOREN_OFF);

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