LPC11u68 ADC Output Wrong

[zaidshaikh]

I am working on LPC11u68 with Keil IDE. I havent used the adc peripheral on this chip before. I am not getting the proper  ADC output. The output which am getting is 0xfff.   Please see my init code and adc_read code  and do let me know what i am doing wrong.

void ADCInit( void)
{
   unsigned char i;
   LPC_SYSCON->SYSAHBCLKCTRL |= (1<<13 |1<<16);          /* Enable AHB clock to the ADC and IOCON */
   LPC_SYSCON->PDRUNCFG &= ~(0x1<<4);                            /* Disable Power down bit to the ADC block. */
   LPC_IOCON->PIO0_11 |= 0x02;                                              // Cnfigure PIO0_11 as ADC9
   LPC_IOCON->PIO0_11 &= ~(3<<3);                                         //Disable the internal pull up.
   LPC_IOCON->PIO0_11 &= ~(1<<7);                                         //Configure PIO0_11 as analog pin
   LPC_ADC->CTRL |= 47;                                                           //ADC clkdiv = val+1 i.e 48. 48M/*48
   LPC_ADC->TRM &= ~(1<<5);
   LPC_ADC->SEQA_CTRL &= ~(1<<31);                 //Disable the conversion sequence by setting the SEQ_ENA bit to 0
   LPC_ADC->SEQA_CTRL |= 1<<18;                       //Set the TRIGPOL bit to 1 in the in the SEQA_CTRL register
   LPC_ADC->SEQA_CTRL |= 1<<31;                       //Enable the conversion sequence by setting the SEQ_ENA bit to 1
}

unsigned int ADCRead( unsigned char channelNum )
{
unsigned int regVal, ADC_Data;

LPC_ADC->SEQA_CTRL |= 1<<channelNum;      //  select channel for conversion
LPC_ADC->SEQA_CTRL |= 1<<26;                     //start adc conversion
while ( 1 )                                                               /* wait until end of A/D convert */
{
regVal = LPC_ADC->SEQA_GDAT;
if ( regVal & ADC_DONE )
{
break;
}
}
if ( regVal & ADC_OVERRUN )                      /* save data when it's not overrun, otherwise, return zero */
{
return ( 0 );
}
ADC_Data = ( regVal >> 6 ) & 0x3FF;
return ( ADC_Data );                                  /* return A/D conversion value */

}

[zaidshaikh]

Actually the Analog input supply voltage was not provided. The code was ok.

[Carlos_Mendoza]

Hi Zaid,

It is good to hear the program is now working correctly. If you need more information on how to configure the ADC I would recommend that you take a look to the LPCOpen examples:

LPCOpen Software for LPC11XX|NXP 

Hope it helps!

Best Regards,
Carlos Mendoza
Technical Support Engineer

[zaidshaikh]

Also the Vrefp is 3.3V and Vrefn is 0V.