[SOLVED] dspic33f ADC Multiple Channels Help

[bubble_d]

Hi Everyone,

So I need help Implementing a 4 channel ADC where I read 4 voltages.

So far I have one ADC working, but I dont really understand how I would do multiple adc sampling.

When I initialize my ADC, do I just need to change my AD1PCFGH (Analog inputs) to select my four input pins?

Also I am unsure how to read the voltages of three channels, do i need four ADC read functions where I return 4 separate buffers which will give me my voltage?

Here is what I have for now: (ADC.h)

void initADC( int amask)
{
    AD1PCFGH = amask;      // select analog input pins
    AD1CON1 = 0x00E0;     // data output format-integer, auto convert after end of sampling.12bit Operation mode. No need to include a delay loop to provide time for completion of sampling
    AD1CSSL = 0;          // no scanning required
    AD1CON3 = 0x1FFF ;     // Use internal clock, max sample time avail is 31Tad, conversion time Tad = 128*Tcy = 128*(2/Fosc) = 256/8MHz = 32us which is > (required)75ns ); 31 Tad = 31*32us = 992us is the sample time. About 100samples/sec
    //Possibly 1FFFF Check Both
	AD1CON2 = 0;          // use MUXA, AVss and AVdd are used as Vref+/-
    AD1CON1bits.ADON = 1; // turn on the ADC
} //initADC


int readADC1( int ch)
{
    AD1CHS0  = ch;               // select analog input channel
    ADC1BUF0 = 0x0000;   		// Reset Buffer
    AD1CON1bits.SAMP = 1;       // start sampling, automatic conversion will follow at end of sampling   
    while (!AD1CON1bits.DONE);  // wait to complete the conversion. DONE will be set as soon as conversion ends
    return ADC1BUF0;            // read the conversion result
} // readADC


//Forth Module is used for now because it is easy to access in hardware setup
int readADC4( int ch)
{
    AD1CHS0  = ch;               // select analog input channel
    ADC1BUF0 = 0x0000;   		// Reset Buffer
    AD1CON1bits.SAMP = 1;       // start sampling, automatic conversion will follow at end of sampling   
    while (!AD1CON1bits.DONE);  // wait to complete the conversion. DONE will be set as soon as conversion ends
    return ADC1BUF0;            // read the conversion result
} // readADC

Obviously I am getting errors that are telling me ADC1BUF1 is undeclared.



Can anyone help me out? Or even lead me in the right direction with an example?

Thank you.

[EDIT] I just realized there is no ADC1BUF0 . I guess Im looking into this all wrong... I set it to ADC1BUF0 and the program ran but I was getting the max voltages (I.e the voltages added together but it clips at 3.3) How do I do this!~!!

 

[GSM Man]

IN 10-bit mode the ADC can sample 4 channels simultaneously, however in 12-bit mode you have to sample and convert them one-by-one. The following code should allow you to convert any single-channel:

int readADC(int channel)
{
	AD1CHS0bits.CH0SA = channel;			// Select the channel to convert
	IFS0bits.AD1IF = 0; 					// Clear ADC interrupt flag
	AD1CON1bits.DONE=0;						// Clear Done Flag
	AD1CON1bits.SAMP=1; 					// Start sampling 

	while(IFS0bits.AD1IF == 0);				// Wait for conversion complete

	AD1CON1bits.ASAM = 0; 					// Then stop sample/convert...
	return(ADC1BUF0);
}

 

[bubble_d]

I applied the code you gave me and then sampled two channels and I got readings but both the variables I set to hold the ADC1BUF0 values given by the ADC seem to add together instead of seperating the two values.

I.E I have 3.7 Volts entering RB3 and(I use a voltage divider to be able to hangle voltages >3.3) and 4.1 Volts entering RB8, Although when I show either voltages I get 6.6V (I.E max 3.3 V due to multiplier to cancel out voltage divider). I would expect it to show 3.7 V for one variable and 4.1 V for the other. Any Ideas?

This is my Main Code:

#include <stdio.h>
#include <stdlib.h>
#include "p33FJ256GP710a.h"
#include "lcd.h"
#include "ADC.h"
#include "delay.h"

//ADC CHANNELS
// Each channel was selected such that a ground pin is right next to the input
// pin while the pin needed to be a ADC pin
#define Moduleinit 0x0108
#define B1ADC 3 //AN3 Selected for 'Battery Module' 1
#define B2ADC 0 //AN0 Selected for 'Battery Module' 2
#define B3ADC 1 //AN1 Selected for 'Battery Module' 3
#define B4ADC 8 //AN8 Selected for 'Battery Module' 4
// Buttons
#define SW1 PORTDbits.RD6
#define SW2 PORTDbits.RD7
#define SW4 PORTDbits.RD13
//LEDS
#define LED1 LATAbits.LATA0
// I will start with A single battery module then once this
// works will I continue with all the modules.

//***************************************************************

_FOSC(OSCIOFNC_ON & FCKSM_CSDCMD & POSCMD_NONE);	//Oscillator Configuration
_FOSCSEL(FNOSC_FRC);								//Oscillator Selection
_FWDT(FWDTEN_OFF);									//Turn off WatchDog Timer
_FGS(GCP_OFF);										//Turn off code protect
_FPOR( FPWRT_PWR1 );								//Turn off power up timer

void Update_LCD( void );
double voltage1;
double voltage2;
const char mytext[] = "hello";
const char mytext1[] = "EDP 2013";
const char mytext2[] = "shitz";
const char mytext3[] = "Holla";
const char mytext4[] = "fuck you";
char result [24];

int main(void)
{

	//Variables For Switches
	int	SW1Pressed=0;
	int	SW2Pressed=0;
	int	SW4Pressed=0;
	double v1 =0;
	double v2=0;

	TRISA = 0x007E;			//Make all PORTs all outputs
	/* Initialize LCD Display */
	Init_LCD();
	/* Welcome message */
	home_clr();
	puts_lcd( (char*) &mytext[0] );
	line_2();
	puts_lcd("BITCHES");
	
	initADC(Moduleinit);

	TRISB = 0x0108; //Sets RB3/AN3 as input since AN3 is being used as analog Input
	

	while(1)
	{				// delay 200ms
	

		
		

		if(SW1Pressed==1){
		
		home_clr();
		
		v1 = readADC(B1ADC); //Read ADC
		voltage1 = (v1/1024)*6.6;
	
		

		sprintf(result,"Voltage: %0.2f",voltage1);
		puts_lcd(&result);
		Delay(50);
}else if(SW2Pressed==1){

	home_clr();
		
		v2 = readADC(B4ADC); //Read ADC
		voltage2 = (v2/1024)*6.6;
	
		

		sprintf(result,"Voltage: %0.2f",voltage2);
		puts_lcd(&result);
		Delay(50);

}

		if(!SW1){
		
		SW1Pressed=1;
		SW2Pressed=0;
		SW4Pressed=0;
		

		}else if (!SW2) {
		
			SW1Pressed=0;
			SW2Pressed=1;
			SW4Pressed=0;
		

		}else if (!SW4) {

			home_clr();
		//	Delay(50);
			puts_lcd(&mytext3);
		
		}

		
}
}

 

[GSM Man]

What do you get if you ground one of the pins? What do you get if you ground both of the pins?

 

[bubble_d]

They are both grounded initially and when I only ground one of them, The grounded one Gives me the correct voltage, the other one gives me...0.72 V but it deviates a lot.

 

[GSM Man]

Can you post a schematic?

 

[bubble_d]

The actual hardware design I am using isnt complete, So I temporarily connected my 3.7 V cell to a potentiometer with ground connected to explorer 16 ground, I also connected another module directly to the ADC pin and the ground pin to the ground pin as well. I will send you my actual schematic when I get home.

Thanks.

Oh and I also included a voltage divider so I can handle the 3.7 V which is >3.3v Max


EDIT [Here is my Schematic]

 

[babar_ali]

The grounded one Gives me the correct voltage, the other one gives me...0.72 V but it deviates a lot.

This pin should give "0" if connected to ground. I am attching one of the demo code chunk that i wrote for dsPIC33FJ64MC506A. Have a look and change the extention of the file.

 

[bubble_d]

Once I fixed some errors I got it working

Also my circuit was giving me errors. I plugged in 3 batteries directly and I get 3 different voltages

Thank you everyone