problem with printf() and ADC

Hi,

I mentioned last week (in "problem with putchar()" thread) that I found my code acting strange when a variable called counter1 keeps incrementing while printing values to the serial port during simulation, even though it is not coded to do so.

Basically my program is set to generate analog-to-digital conversions every millisecond (1kHz) on a 100Hz sine wave I have connected to ADC0 input on the Microconverter SAR A3 evaluation board from analog devices which uses an ADuC841 MCU. In the ADC interrupt routine, I basically save the first 12-bit ADC value in a structure and for the next 254 values, I subtract them from the previous sample and save them in the same structure. When my structure is full (i.e. has 255 values and a counter value, counter1), I write the values stored in the structure to the serial port. The problem is when I use printf() or putchar(), the value of my counter increments when I simulate my program and I cant see why, since the program execution does not jump to my ADC ISR. I thought maybe this is a problem with the simulator but when I download the code to the evaluation board and view the output on Hyperterminal, the count values do not match up with the number of values printed. Obviously in the simulator I cannot see the type of values I'm getting as the ADCDATAH/L are always 0. I have tried to look at the trace results when placing a breakpoint at the counter1 variable but am still not sure whats happening.

I am new to the whole MCU environment and was wodering if anyone can help. I have placed my code below in case I have not clarified my problem.

Thanks,
Lisa

#include <stdio.h>
#include <ADuC841.h>

#define MAX_COUNT 255

sbit LED = 0xB4;
unsigned char a = 5;
unsigned char channel_to_convert = 0;
unsigned char count, counter1 = 2; // doesn't need to go above 255 for now! Initialize to 1 to skip member count in structure
unsigned char error = 0;
unsigned char finished = 0;
bit buf = 0;

short adc_value, temp1, temp2;
unsigned char i;
//int t1,t2;

struct record1
{
	unsigned char cnt;
	short base_value;
	char x[253];
};

struct record1 rec1[2];                  // array variable rec1 of type struct record1


// ADC Interrupt Service Routine */
void adc_int() interrupt 6
{
	LED =0;

	// Store the first value into the second element of one array
	if (counter1 == 2)
	{
		counter1++;
		rec1[buf].base_value = (ADCDATAL | ((ADCDATAH & 0x0F) << 8));
		temp1 = rec1[buf].base_value;
	}

	else
	{
		if (counter1 < MAX_COUNT)
		{
			adc_value = (ADCDATAL | ((ADCDATAH & 0x0F) << 8));
			temp2 = adc_value - temp1;
			temp1 = adc_value;

			if((temp2 >> 8) == 0) // if dpcm values are <= 1 byte
			{
				rec1[buf].x[counter1-3] = (char) temp2;
				counter1++;
			}

			else
			{
				error = 1; // error will be 1 if a dpcm value (temp2) > 8 bits
			}
		}

		else
		{
		 	adc_value = (ADCDATAL | ((ADCDATAH & 0x0F) << 8));
			temp2 = adc_value - temp1;

			if((temp2 >> 8) == 0) // if dpcm values are <= 1 byte
			{
				rec1[buf].x[counter1-3] = (char) temp2;
			}

			else
			{
				error = 1;
			}

			finished = 1;
			// exit the Interrupt and print to serial port in main function
		}
	}
	TF2 = 0; // clear overflow flag
	LED =1;
	return;
}


int main(void)
{
	//t1 = &counter1;
	//t2 = &i;
// Set up UART at 115,200 Baud -> may have to alter */
	T3CON = 0x82; // DIV=2
	T3FD = 0x20; // T3FD = 32
	SCON   = 0x52;

	/* Configure ADC */
	ADCCON1 = 0x9E;      				// power up ADC
	ADCCON2 = channel_to_convert;		// select channel to convert

	RCAP2L  = 0xCD; 		            // sample period = 1 ms
	RCAP2H  = 0xD4;
	TL2	= 0xCD;
	TH2	= 0xD4;

	EA = 1;			  					// enable interrupts
	EADC = 1;							// enable ADC interrupt
	//ET2 = 1;		  					// If timer 2 interrupt is present, enable it
	TR2	= 1;							// run Timer2


	while(1)
	{
		if(finished)
		{
			rec1[buf].cnt = counter1; // store counter1 value in 1st element of array

			buf ^= 1;  // set alternative buffer up so values wont be overwritten during printing
			counter1 = 2; // reset counter1 to original value

			// print out whole structure
			printf("%02BX ",rec1[!buf].cnt);
			printf("%02BX ",(char) (rec1[!buf].base_value >> 8)); // need to split integer into 2 chars
			printf("%02BX ",(char) (rec1[!buf].base_value));

		//	putchar(rec1[!buf].cnt);
		//	putchar((char) (rec1[!buf].base_value >> 8));
		//	putchar((char) (rec1[!buf].base_value));

			for(i = 0; i < MAX_COUNT-2; i++)
			{
				printf("%02BX ",rec1[!buf].x[i]);
				//printf("%02BX ", i);
				//putchar(rec1[!buf].x[i]);
			}

			printf("\n");
			finished = 0; // reset finished condition
		}

		if(error)
		{
			rec1[buf].cnt = counter1; // store counter1 value in 1st element of array
			count = counter1;
			buf ^= 1;  // set alternative buffer up
			counter1=3; // want to start back at first if loop in first else loop in interrupt
			rec1[buf].base_value = temp1;	// keep the current value of temp1 as base_value for next structure

			// print out whole structure
			printf("%02BX ",rec1[!buf].cnt);
			printf("%02BX ",(char) (rec1[!buf].base_value >> 8));
			printf("%02BX ",(char) (rec1[!buf].base_value));

			for(i = 0; i < count; i++)
			{
				printf("%02BX ",rec1[!buf].x[i]);
			//	printf("%02BX ", i);
				//putchar(rec1[!buf].x[i]);
			}

			printf("\n");
			error = 0; // reset the error condition
		}
	}

}