Analog comparator 1 on Tiva Launchpad

ISHAN SHAH1

Other Parts Discussed in Thread: TM4C123GH6PM

Hi all,

I am trying to configure analog comparator 1 on tiva launchpad. Neither I am able to read the output of comparator not I am seeing any output on pin PF1, which is output of comparator 1 on launch pad. I have set internal reference voltage to 1.65 V. and I am giving input on pin PC4.

Below is my code:

#include "inc/tm4c123gh6pm.h"
#include <stdbool.h>
#include <stdint.h>
#include "inc/hw_memmap.h"
#include "driverlib/gpio.h"
#include "driverlib/pin_map.h"
#include "driverlib/pwm.h"
#include "driverlib/sysctl.h"
#include "inc/hw_types.h"
#include "driverlib/debug.h"
#include "driverlib/adc.h"
#include "driverlib/interrupt.h"
#include "driverlib/comp.h"

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

int32_t Comp_out = 0 ;

int main(void)
{
SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_PLL | SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ);

SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOC); // enable port C
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF); // '' '' F

SysCtlPeripheralEnable(SYSCTL_PERIPH_COMP1); // enable comparator 1

GPIOPinTypeComparator(GPIO_PORTC_BASE, GPIO_PIN_5); // assign pin type
GPIOPinTypeComparator(GPIO_PORTC_BASE, GPIO_PIN_4);
GPIOPinTypeComparator(GPIO_PORTF_BASE, GPIO_PIN_1);

GPIOPinConfigure(GPIO_PC4_WT0CCP0); // pin configure
GPIOPinConfigure(GPIO_PC5_WT0CCP1);
GPIOPinConfigure(GPIO_PF1_C1O);

ComparatorConfigure(COMP_BASE, 1, COMP_TRIG_NONE|COMP_ASRCP_REF|COMP_INT_HIGH| COMP_OUTPUT_NORMAL); // comparator configure
ComparatorRefSet(COMP_BASE, COMP_REF_1_65V); // set internal reference voltage

SysCtlDelay(SysCtlClockGet() / 96); // delay

while(1)
{
SysCtlDelay(2000);

Comp_out = ComparatorValueGet(COMP_BASE, 1); // read comparator output

SysCtlDelay(2000);
}

}

Please let me know what is missing in the code. and what do I need to get output on pin PF1.

Regards,

Ishan

over 11 years ago

0 cb1_mobile over 11 years ago

Guru 117855 points

Quickly - can these be correct?

GPIOPinConfigure(GPIO_PC4_WT0CCP0); // pin configure

GPIOPinConfigure(GPIO_PC5_WT0CCP1);

Past assisted you - related comparator issue. Here's our "known good" Analog Comparator set-up/config: Note: Comp_0 - we feed external voltage signals into both Comp + and Comp -. (internal too limiting {too coarse} - for our usage) Note that earlier, elsewhere - we liberated PF0 from its restrictive, NMI fate... And this code via StellarisWare 9453 - used w/LX4F...

        ROM_ComparatorConfigure(COMP_BASE, 0, (COMP_TRIG_NONE |
                                COMP_ASRCP_PIN0 | COMP_OUTPUT_NORMAL));

        ROM_GPIOPinConfigure(GPIO_PF0_C0O); // Comp Output

ROM_GPIOPinTypeComparator(GPIO_PORTC_BASE, GPIO_PIN_6 | GPIO_PIN_7);

Note that you "read" the comparator - much as we do. Here's our code - enabling scope-free (i.e. Led) Comp verify:

          while (1)
          {
                k = ROM_ComparatorValueGet(COMP_BASE, 0);

                     if (k == 1)
                    {
                         HWREG(GPIO_PORTD_BASE + GPIO_O_DATA + (0x40 << 2 )) |= 0x40; // Comp Led ON
                   }
                    else
                    {
                        HWREG(GPIO_PORTD_BASE + GPIO_O_DATA + (0x40 << 2)) &= ~(0x40); // Comp Led OFF
                    }

              ROM_SysCtlDelay(40000);
          }

0 ISHAN SHAH1 over 11 years ago in reply to cb1_mobile

Intellectual 370 points

Hi,

Thank you for assisting me again.

I removed below lines. Yes it was big mistake .

GPIOPinConfigure(GPIO_PC4_WT0CCP0); // pin configure

GPIOPinConfigure(GPIO_PC5_WT0CCP1);

now I can read the comparator value but still no sign of output of PF1.

Code now is in sequence that you suggested.

GPIOPinConfigure(GPIO_PF1_C1O);
GPIOPinTypeComparator(GPIO_PORTC_BASE, GPIO_PIN_4 | GPIO_PIN_5);
SysCtlDelay(SysCtlClockGet() / 96); // delay

I am interested in output on pin PF1, because like your, I also like to feed it into another MCU.

Regards,

Ishan

0 cb1_mobile over 11 years ago in reply to ISHAN SHAH1

Guru 117855 points

Not to feel bad - Analog Comparator function is fairly new - and not much detailed - anywhere obvious - that we could find. Much trial/error - yielded our findings.

To insure an output - voltage level upon Comp + must exceed that upon Comp -. (assumes you have set-up as our code shows - which avoids use of internal Ref V - for test simplicity.)

I past reported that Comp Out did not require pull-up - on our LX4F device. (tested across multiple boards - multiple MCUs) Cannot hurt for you to add pull-up R (4K7 - 10K) to your Comp Out - to see if that aids. Again - I'd eliminate the internal V Ref (at least for early stage testing) - use code provided - and observe (and report) results...

And - insure that your Comp Out is not tied to another pin - which may default into "output" - and "collide" w/ Comp Out!

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Analog comparator 1 on Tiva Launchpad