I cannot cause the status of the Analog Comparator to change the status with varying input voltage.
COMP_ACSTAT0_R always returns 0x0020
Gone through this 3 times without success , need help from you folks
Tiva launch pad TM4C123G
CCS 5.3
// ***************************************************************************
// PF1 = RED led
// PF2 = BLUE led
// PF3 = GREEN led
// PF0 = SW2
// PF4 = SW1
// PC6 = Comparator 0 input
//
// PC6
// |
// V
// 3.3V----\/\/\/\-----gnd
//
// ****************************************************************************
#include <stdint.h>
#include "tm4c123gh6pm.h"
#define SYSDIV 2
#define LSB 0
#define red 0x0002
#define blue 0x0004
#define green 0x0008
volatile uint32_t ui32Loop; //
//*****************************************************************************
//
//
//*****************************************************************************
int
main(void)
{
//*********************************************************************
// init Clock
//*********************************************************************
SYSCTL_RCC2_R |= SYSCTL_RCC2_USERCC2;
SYSCTL_RCC2_R |= SYSCTL_RCC2_BYPASS2;
SYSCTL_RCC_R &= ~SYSCTL_RCC_XTAL_M; // clear XTAL field
SYSCTL_RCC_R += SYSCTL_RCC_XTAL_16MHZ; // configure for 16 MHz crystal
SYSCTL_RCC2_R &= ~SYSCTL_RCC2_OSCSRC2_M; // clear oscillator source field
SYSCTL_RCC2_R += SYSCTL_RCC2_OSCSRC2_MO; // configure for main oscillator source
SYSCTL_RCC2_R &= ~SYSCTL_RCC2_PWRDN2;
SYSCTL_RCC2_R |= SYSCTL_RCC2_DIV400;
SYSCTL_RCC2_R &= ~SYSCTL_RCC2_SYSDIV2_M; // clear system clock divider field
SYSCTL_RCC2_R &= ~SYSCTL_RCC2_SYSDIV2LSB; // clear bit SYSDIV2LSB
SYSCTL_RCC2_R += (SYSDIV<<23)|(LSB<<22); // divide by (2*SYSDIV+1+LSB)
while((SYSCTL_RIS_R&SYSCTL_RIS_PLLLRIS)==0){};
SYSCTL_RCC2_R &= ~SYSCTL_RCC2_BYPASS2;
// ********************************************************************************
// enable device clocks
// ********************************************************************************
SYSCTL_RCGCGPIO_R |= SYSCTL_RCGCGPIO_R4 + SYSCTL_RCGCGPIO_R5;// enable GPIO E & F
// Do a dummy read to insert a few cycles after enabling the peripheral.
ui32Loop = SYSCTL_RCGC2_R;
// *************************************************************************
// Enable the GPIO pin for the LED (PF3). Set the direction as output, and
// enable the GPIO pin for digital function.
// *************************************************************************
GPIO_PORTF_DIR_R = 0x0E;
GPIO_PORTF_DEN_R = 0x0E;
ui32Loop = SYSCTL_RCGC2_R;
GPIO_PORTF_DATA_R &= ~(0x0E);
// *************************************************************************
// configure Comparator
// C0+ 14 PC6 I Analog Analog comparator 0 positive input.
// *************************************************************************
SYSCTL_RCGCGPIO_R |= SYSCTL_RCGCGPIO_R2; // enable GPIO Clock C
SYSCTL_RCGCACMP_R = SYSCTL_RCGCACMP_R0; // enable comparator clock
GPIO_PORTC_AFSEL_R |= GPIO_6; // assign PC6 as analog
GPIO_PORTC_AMSEL_R = 0x00; // *set to analog
COMP_ACREFCTL_R |= COMP_ACREFCTL_EN + COMP_ACREFCTL_RNG + 0x00000007; // internal voltage reference to 1.65 V
COMP_ACCTL0_R |= COMP_ACCTL0_ASRCP_REF + COMP_ACCTL0_ISEN_M; // use the internal voltage reference
GPIO_PORTF_DATA_R &= ~(red); // reset, turn off LEDS
GPIO_PORTF_DATA_R &= ~(green);
GPIO_PORTF_DATA_R &= ~(blue);
while(1) // loop forever
{
if (COMP_ACSTAT0_R == 0x00000000 ) // test if set
{
GPIO_PORTF_DATA_R |= green; //1 VIN- < VIN+ current output value
// COMP_ACSTAT_R value remains 0x0020 even though I change the input voltage.
// what am I missing ???????
}
else
{
GPIO_PORTF_DATA_R &= ~(green);
}
}
}
// *****************************************************************
// end of Main
// *****************************************************************
