Frank Vannieuwkerke / ComparatorIn

KL25Z Comparator library

Dependents:   ComparatorIn_demo TEMT6200_demo 05_comparator_demo 05_comparator_demo ... more

KL25Z Comparator library

Comparator features

Block diagram

/media/uploads/frankvnk/kl25z_comparator_block_diagram.jpg

Introduction

This library allows us to create comparator objects between different inputs.
The comparator + and - inputs can be routed to one out of eight reference inputs (see table).
Input selection

Pin name#MUX inputCMP0Comment
PTC6000IN0CMP0_IN0
PTC7001IN1CMP0_IN1
PTC8010IN2CMP0_IN2
PTC9011IN3CMP0_IN3
PTE30100IN4CMP0_IN412-bit DAC0
PTE29101IN5CMP0_IN5
110IN61V internal Bandgap*
NC111IN7internal 6-bit DAC0
(table 1)

* Not yet implemented

Using the library

Selecting pins on initialisation
Upon initialisation, the comparator registers are set to following values:

    CMP0->CR0   = 0x00;  // Filter and digital hysteresis disabled
    CMP0->CR1   = 0x17;  // Continuous mode, high-speed compare, unfiltered output, output pin disabled
    CMP0->FPR   = 0x00;  // Filter disabled
    CMP0->SCR   = 0x06;  // Disable all interrupts and clear flags (flags are cleared by this write)
    CMP0->DACCR = 0xE0;  // DAC enabled, Vdd is 6bit reference, threshold set to 1/2 of full-scale (1.65V)

The library accepts two input parameters:
example:

ComparatorIn compi(PTC8, NC);

notes

Example
Following code demonstrates interrupt callback and polling mode.
Note: Polling the comparator this way won't always trigger the printf because of the wait() instructions (if we go above and below the threshold during the wait() time, then the polling cannot not see this change).

/***********************************************************
CODE EXAMPLE FOR AMBIENT LIGHT SENSOR ON KL25Z + Wi-Go BOARD
 ***********************************************************/
#include "ComparatorIn.h"
#include "mbed.h"

DigitalOut blinker(LED_BLUE);
DigitalOut cmpled(LED_GREEN);
DigitalOut cmp_en (PTD5);
AnalogIn cmp_lvl (PTB0);
ComparatorIn compi(PTC8, NC); // in+ = PTC8, in- = internal 6-bit DAC 

// Comparator callback functions
void cmp_rise_ISR(void)
{
    cmpled = 0;
}

void cmp_fall_ISR(void)
{
    cmpled = 1;
}

int main()
{
    cmp_en = 1;
    cmpled = 1;

    compi.rising(&cmp_rise_ISR);                // Set pointer to rising interrupt function
    compi.falling(&cmp_fall_ISR);               // Set pointer to falling interrupt function
    compi.treshold(0.5);                        // Set comparator threshold to 1.65V = 32 * 3.3V / 64

    while(1)
    {
        printf("Light sensor : %7.5f Volt\n",cmp_lvl*3.3);
        blinker = 1;
        wait(1);
        blinker = 0;
        wait(0.2);
        if (compi.status() == 0x01)
        {
            printf("*** Treshold reached : %7.5f\n",cmp_lvl*3.3);
        }
    }
}


Notes

compi.rising(&cmp_rise_ISR);
compi.falling(&cmp_fall_ISR);
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