PIC32MZ tutorial -- Input Capture

　　Today I accomplish a simple application for PIC32MZ EC Starter Kit. This application uses Input Capture feature of PIC32MZ. The Input Capture module captures the 32-bit value of the selected Time Base registers when an event occurs at the ICx pin.  The timer source for each Input Capture module depends on the setting of the ICACLK bit in the CFGCON register. To change this bit, the unlock sequence must be performed. In the implementation I just use IC1 to capture the 32-bit timer with combining Timer2 and Timer3.

　　First, see the 32-bit timer initialization.

void T32_Init(void)
{
    T2CON = 0x0;
    T3CON = 0x0;
    TMR2 = 0;
    TMR3 = 0;
    
    PR3 = 0xFFFF;
    PR2 = 0xFFFF;

    T2CON = 0x8008;
}

　　I use PPS to set RB14 as IC1. And I define a array IC1_ST.buf[] to store capture valure. there is a point to clarify. To set IC1CON, if using one sentence like "IC1CON = 0x8012;"  It will cause a input capture interrupt. It is not expectation. Instead of setting IC1CON with one sentence, I use two sentences like below.

　　IC1CON = 0012;

　　IC1CON |= 0x8000;

Enable IC1CON last then input capture works as expectation. For the detail, please see the interface of IC1.

// In IC.h
#define SIZE_MAX 20
    typedef struct _IC_ST_t{
        unsigned int count;
        unsigned long buf[SIZE_MAX];
    } IC_STR_t;
    
    extern IC_ST_t IC1_ST;
 
void IC1_Init(void);
unsigned long IC1_ReadCapture(void);

// In IC.c
IC_ST_t IC1_ST;

void IC1_Init(void)
{
    //AN9|RPB14|RB14 with digital IO, disable AN first
    ANSELB &= 0xFFFFBFFF;
    TRISBSET = 0x4000;
    //Enable internal pull-up
    CNPUBSET = 0x4000;
    
    // Interrupt with priority 7 and sub-priority 0
    IPC1SET = 0x1C0000; 
    IFS0CLR = 0x40;
    IEC0SET = 0x40;
    // RPB14 set as IC1 with PPS
    IC1R = 0x2;
    IC1CON = 0x0102;

    IC1_ST.count = 0;
    unsigned int i;
    for ( i = 0; i < SIZE_MAX; i++)
    {
        IC1_ST.buf[i] = 0;
    }
    
    IC1CON |= 0x8000;
}

unsigned long IC1_ReadCapture(void)
{
    while ((IC1CON & 0x8) == 0x8)
    {
        if (IC1_ST.count == SIZE_MAX)
        {
            IC1_ST.count = 0;
        }
        IC1_ST.buf[IC1_ST.count++] = IC1BUF;
    }
}

　　The final, see the main function and interrupt service routine.

#include <sys/attribs.h>
#include "T32.h"
#include "IC.h"
#include "CFB.h"

#define LED_IOCTL()       TRISHCLR = (1<<0)
#define LED_SETON()       LATHSET = (1<<0)
#define LED_SETOFF()      LATHCLR = (1<<0)
#define LED_ONOFF()       LATHINV = (1<<0)
#define LED_OPEN()        ANSELH &= 0xFFFFFFFE

#define Mvec_Interrupt() INTCONSET = 0x1000; asm volatile("ei")

void __ISR(_INPUT_CAPTURE_1_VECTOR,ipl7AUTO) IC1_Handler(void)
{
    LED_ONOFF();
    IC1_ReadCapture();
    IFS0CLR = 0x40;
}
void main(void)
{
    LED_OPEN();
    LED_IOCTL();
    T32_Init();
    IC1_Init();
    Mvec_Interrupt();
    while(1)
    {
        ; // do nothing
    }
}

　　On the PIC32MZ EC Starter Kit, RB14 connects to a push button. I push down this button with 1 Hz frequency. I can see my array IC1_ST.buf[] filled with values indicating a frequency of 1 Hz frequency in debug mode.