ADC on Tiva C Series

[RAKSH 1]

I'm trying to read analog values from a photoresistor(off of a voltage divider) connected to pin PC5 .
I use the following code 

 

#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "driverlib/debug.h"
#include "driverlib/sysctl.h"
#include "driverlib/adc.h"
#include "driverlib/gpio.h"

#ifdef DEBUG
void__error__(char *pcFilename, uint32_t ui32Line)
{
}
#endif

int main(void)
{
uint32_t ui32ADC0Value[1];


SysCtlClockSet(SYSCTL_SYSDIV_5|SYSCTL_USE_PLL|SYSCTL_OSC_MAIN|SYSCTL_XTAL_16MHZ);

SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOC);
    GPIOPinTypeADC(GPIO_PORTC_BASE,GPIO_PIN_5);
ADCSequenceConfigure(ADC0_BASE, 3, ADC_TRIGGER_PROCESSOR, 0);
 ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH0 | ADC_CTL_IE |ADC_CTL_END);

ADCSequenceEnable(ADC0_BASE, 3);

  ADCIntClear(ADC0_BASE, 3);
while(1)
{
ADCProcessorTrigger(ADC0_BASE, 3);

  while(!ADCIntStatus(ADC0_BASE, 3, false))
  {
  }
  ADCIntClear(ADC0_BASE, 3);

  ADCSequenceDataGet(ADC0_BASE, 3, ui32ADC0Value); // Watch on ui32ADC0Value
 

  SysCtlDelay(20000);

}
}

 

 

But unfortunately I'm getting random values of ui32ADC0Value that don't correspond to the ambient light .
What am i doing wrong here ? 

[pao 0]

HI @

Which your Microcontroller ?  Do you have 'Tiva C Series LaunchPad ( EK-TM4C123GXL) ?

 

 

if you have 'Tiva C Series LaunchPad', you can connect pin 'PE3'

 

GPIO_PORTC_BASE ==> GPIO_PORTE_BASE

 

SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
GPIOPinTypeADC(GPIO_PORTE_BASE,GPIO_PIN_3);
ADCSequenceConfigure(ADC0_BASE, 3, ADC_TRIGGER_PROCESSOR, 0);
ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH0 | ADC_CTL_IE |ADC_CTL_END);

[L.R.A 78]

Btw this seemed important:

http://e2e.ti.com/support/microcontrollers/tiva_arm/f/908/t/294691.aspx

[RAKSH 1]

Thanks but I resolved my issue .
The problem was , I was using a wrong channel to read values .
And also ,that it is necessary to clear all Interrupts on the ADC before proceeding .

Thanks a lot guys !

[veimmone 0]

Btw this seemed important:

http://e2e.ti.com/support/microcontrollers/tiva_arm/f/908/t/294691.aspx

 

Not really relevant in this case, it only affects unregistering an interrupt handler. For most projects, this is not needed. Plus, it works perfectly well on ADC0

 

Best,

Veikko