ADC Interrupt and UART (delay issues)

Hi, 

I am very new to using microcontroller. I have been assigned to read an ADC Value using a timer interrupt, then UART-ing the results. The problem I am encountering is when a UART statement is present in the timer interrupt, the result is a delayed timer interrupt. For example, I am sampling a 50Hz sine wave in 12800Hz to produce 256 sample points in one period. I am able to produce the result correctly without UART, but once UART  (even a simple \n\f printf) is added, the sample points span across 3 periods. I suspect this is due to delay in sampling.

I hope i make myself clear. Is there any workaround for this? Perhaps i shouldn't place UART in a timer interrupt of 12800Hz.

void Timer0IntHandler(void)
{
	TimerIntClear(TIMER0_BASE, TIMER_TIMA_TIMEOUT);
	ADCIntClear(ADC0_BASE, 0);
		ADCProcessorTrigger(ADC0_BASE, 1);
		while(!ADCIntStatus(ADC0_BASE, 1, false))
		{}

		ADCSequenceDataGet(ADC0_BASE, 1, data);
		dataavg=(data[0]+data[1]+data[2]+data[3])/4;

		if (j==256)
		{
			return;
		}

		else
		{
			if (dataavg>2048)
					{
						ACVoltage[j]= (dataavg-2048)*3.4/2048.00;
//						UARTprintf("%d\n\r", dataavg); 
						j++;
					}

					else
					{
						ACVoltage[j]= -((2048-dataavg)*3.4/2048.00);
//						UARTprintf("%d\n\r", dataavg);

						j++;
					}

		}

}

* The UARTprintf produces delay.