InputCapture

Input capture measures period. More...

Files
file	InputCapture.h
	Software driver functions for input capture.

Macros
#define	INPUTCAPTUREUSELFCLK   2
	use INPUTCAPTUREUSELFCLK to select 32768 Hz LFCLK
#define	INPUTCAPTUREUSEMFCLK   4
	use INPUTCAPTUREUSEMFCLK to select MFCLK (not tested)
#define	INPUTCAPTUREUSEBUSCLK   8
	use INPUTCAPTUREUSEBUSCLK to select BUSCLK

Functions
void	InputCapture_Init (uint32_t timerClkSrc, uint32_t timerClkPrescale, uint32_t priority)
	Initialize input capture. More...
void	InputCapture_InitDual (uint32_t timerClkSrc, uint32_t timerClkPrescale, uint32_t priority)

Detailed Description

Input capture measures period.

Input capture pins

Pin	Timer	Description
PA12	TIMG0	interrupts on rising edge of PA12

Function Documentation

InputCapture_Init()

void InputCapture_Init	(	uint32_t	timerClkSrc,
		uint32_t	timerClkPrescale,
		uint32_t	priority
	)

Initialize input capture.

Arm interrupts on rising edge of PA12
Let P be the period of the selected clock
resolution = P*(timerClkPrescale+1)
precision = 16 bits
range = 65535*resolution (max)
timerClkDivRatio = 1
timerClkFreq = (timerClkSrc / (timerClkDivRatio * (timerClkPrescale + 1)))
resolution = (timerClkDivRatio * (timerClkPrescale + 1)))/timerClkSrc
User defines their own ISR like the following

uint32_t Data[20];
uint32_t Index=0;
uint32_t Time,Last,Period;
uint32_t iidx,count=0;
void TIMG0_IRQHandler(void){
  count++;
  iidx = TIMG0->CPU_INT.IIDX;// this will acknowledge
  if((iidx) == 5){ // 5 means capture CCD0
    Time = TIMG0->COUNTERREGS.CC_01[0]; // time now
    Period  = (Last-Time)&0xFFFF; // elapsed time since last
    Last = Time;
    if(Index < 20){
      Data[Index] = Period;
      Index++;
    }
  }
}

• timerClkSrc
  
  • 2 for 32768 Hz LFCLK
    
  • 4 for MFCLK (not tested)
    
  • 8 for BUSCLK
• For example
  • source=LFCLK, prescale=255, resolution = 7.8125ms
  • source=BUSCLK, prescale=47, resolution = 1us

Parameters

timerClkSrc	could be LFCLK, MFCLK, or BUSCLK
timerClkPrescale	is prescale divide clock by timerClkPrescale+1, 0 to 255
priority	is 0(highest),1,2 or 3(lowest)

Returns

none

Note

Will invoke LaunchPad_Init