main.c

基于at91sam7s256的定时器编程源码

/*--------------------------------------------------------------------------------------
*      ATMEL Microcontroller Software Support  -  ROUSSET  -
*--------------------------------------------------------------------------------------
* The software is delivered "AS IS" without warranty or condition of any
* kind, either express, implied or statutory. This includes without
* limitation any warranty or condition with respect to merchantability or
* fitness for any particular purpose, or against the infringements of
* intellectual property rights of others.
*--------------------------------------------------------------------------------------
* File Name                       : main.c
* Object                          : Initialize a Timer Counter in Capture mode to
*                                 : measure the low period, the high period or the period
*                                 : on a TIOx Input.
*
* Version | mm | dd | yy | author :
*  1.0      05   16   06    PFi   : Creation
*
*--------------------------------------------------------------------------------------
*
* 1)Description:
*
* This test uses one of the timer channel 1 (TC1) in capture mode on TIOA pin to measure
* the period of a signal.
*
* A signal generated on timer channel 0 (TC0) in waveform mode is used to
* generate the signal to capture. The frequency of the signal generated is 1MHz.
*
* 2)Configuration and pins used in this example:
*
* - Input capture on TIOA1
* - Output waveform on TIOA0  @ 1MHZ
* WARNING : These two pins TIOA0 & TIOA1 must be connected together externaly.
*
* 3) Remarks:
*
* This example runs in polling mode.and makes no use of IRQs. To have further details
* and implementation example about using IRQs, refer to any Interrupt project examples,
* like AT91SAM7S64-Interrupt-IAR4_XX-X_X
* available on www.at91.com --> KIT --> AT91SAM7S-EK --> Software
*
***************************************************************************************/

// Include Standard files
#include "project.h"
#include <math.h>     /* use of float */

/* Global variables */
unsigned int volatile TimerCounterClockDiv;

/*----- Types and Constants Definition -----*/

/***********************************************************************
 Configuration of the timer to measure the period of the signal

TIOA    ______                ______________
(input)       |              |              |
              |______________|              |___

              ^              ^              ^
              |              |              |
      reset & start TC   load RA        load RB & disable the TC's Clock

 A TIOA falling edge resets and starts the counter
 A next TIOA rising edge loads RA.
 A TIOA falling edge loads RB (to disable the counter)
 RB contains the duration of the period
*/
/* configuration of the timer to measure the of the signal */
#define MEAS_TIOA_PERIOD (AT91C_TC_LDRA_RISING|AT91C_TC_LDRB_FALLING|AT91C_TC_ABETRG|AT91C_TC_LDBDIS|AT91C_TC_ETRGEDG_FALLING)

/* Load RA with rising edge */
/* Load RB with falling edge and disable counter*/
/* TIOA used as external trigger on a falling edge */
/* RB contains the duration of the period */
/* External trigger on rising edge */
/*************************************************************************/

/*-----------------*/
/* Clock Selection */
/*-----------------*/
#define TC_CLKS                  0x7
#define TC_CLKS_MCK2             0x0  /* Timer Clock = MCK / 2 */
#define TC_CLKS_MCK8             0x1  /* Timer Clock = MCK / 8 */
#define TC_CLKS_MCK32            0x2  /* Timer Clock = MCK / 32 */
#define TC_CLKS_MCK128           0x3  /* Timer Clock = MCK / 128 */
#define TC_CLKS_MCK1024          0x4  /* Timer Clock = MCK / 1024 */

#define MAX_TC_VALUE            0xFFFF /* Max rollover value for 16-bit counter */
#define FALSE 0
#define TRUE 1

#define OUTPUT_FREQ             1000000 /* frequency to generate with timer 0 (in Hz)*/

//*------------------------- Internal Function --------------------------------
//*----------------------------------------------------------------------------
//* Function Name       : AT91F_TC_Open
//* Object              : Initialize Timer Counter Channel and enable is clock
//* Input Parameters    : <pTC> = TC Channel Descriptor Pointer
//*                       <mode> = Timer Counter Mode
//*                     : <TimerId> = Timer peripheral ID definitions
//* Output Parameters   : None
//*----------------------------------------------------------------------------
void AT91F_TC_Open ( AT91PS_TC pTC, unsigned int Mode, unsigned int TimerId)
{
  unsigned int dummy;

  /* First, enable the clock of the TIMER */
  AT91F_PMC_EnablePeriphClock ( AT91C_BASE_PMC, 1<< TimerId ) ;

  /* Disable the clock and the interrupts before to configure it */
  pTC->TC_CCR = AT91C_TC_CLKDIS ;
  pTC->TC_IDR = 0xFFFFFFFF ;

  /* Clear status bit */
  dummy = pTC->TC_SR;

  /* Suppress warning variable "dummy" was set but never used */
  dummy = dummy;

  /* Set the Mode of the Timer Counter */
  pTC->TC_CMR = Mode ;

  /* Enable the clock */
  pTC->TC_CCR = AT91C_TC_CLKEN ;

}

//*----------------------------------------------------------------------------
//* Function Name       : void AT91F_TC_Close ( AT91PS_TC pTC)
//* Object              : Stop a Timer Counter Channel and disable its clock
//* Input Parameters    : <pTC> = TC Channel Descriptor Pointer
//*                     : <TimerId> = Timer peripheral ID definition
//* Output Parameters   : None
//* Functions called    : none
//*----------------------------------------------------------------------------
void AT91F_TC_Close ( AT91PS_TC pTC, unsigned int TimerId )
{
    //* Disable the clock and interrupts
    pTC->TC_CCR = AT91C_TC_CLKDIS ;
    pTC->TC_IDR = 0xFFFFFFFF ;
    //* Stop the Clock of the Timer
    AT91F_PMC_DisablePeriphClock (AT91C_BASE_PMC, 1<< TimerId);
}


//*---------------------------------------------------------------------------------------------------------------
//* Function Name       : AT91F_TimerCounter_MeasureTioaPeriod ( AT91PS_TC pTC, unsigned int Mode, unsigned int TimerId)
//* Object              : Measure TIOA number of MCKI cycles depending on mode
//* Input Parameters    : <pTC> = TC Channel Descriptor Pointer
//*                     : <TimerId> = channel to initialize
//*                     : <Measurement> = Measure the period, low period or high period
//*
//* Output Parameters   : The number of Timer Counter clock cycle
//* Functions called    : none
//*---------------------------------------------------------------------------------------------------------------
unsigned int AT91F_TimerCounter_MeasureTioaPeriod (AT91PS_TC pTC, unsigned int TimerId, unsigned int Measurement)
{
  unsigned int status;

  AT91F_TC_Open ( pTC, Measurement, TimerId);
  while ( ((status = pTC->TC_SR) & AT91C_TC_LDRBS) == 0 );

   //* Suppress warning variable "status" was set but never used
  status = status ;
  return ( pTC->TC_RB ) ;
}

//*---------------------------------------------------------------------------------------------------------------
//* Function Name       : AT91F_TimerCounter_ComputeCompareValue (unsigned int MCK, unsigned int OutputFreq)
//* Object              : Compute the value to write into the compare register (RA, RB or RC) accoring to the
//*                     : Master clock of the system (MCK in Hz) and the frequency of the signal to generate with the timer
//*                     : counter in Hz
//* Input Parameters    : <MasterClock> = Master clock Frequency of the system in Hz
//*                     : <OutputFreq> = Frequency to generate on a TIOx pin in Hz
//*
//* Output Parameters   : Value to write in the RA, RB or RC register.
//* Functions called    : none
//*
//*---------------------------------------------------------------------------------------------------------------
unsigned int AT91F_TimerCounter_ComputeCompareValue (unsigned int MasterClock, float OutputFreq)
{
  float OutputPeriod = (1/OutputFreq) ;
  unsigned int CompareValue ;
  float DivMin ;

  DivMin = OutputPeriod * (MasterClock/MAX_TC_VALUE);

  if ( (DivMin > 0) && (DivMin < 2) )
  {
    DivMin = 2;
    TimerCounterClockDiv = TC_CLKS_MCK2;
  }
  if ( (DivMin > 2) && (DivMin < 8) )
  {
    DivMin = 8;
    TimerCounterClockDiv = TC_CLKS_MCK8;
  }
  if ( (DivMin > 8) && (DivMin < 32) )
  {
    DivMin = 32;
    TimerCounterClockDiv = TC_CLKS_MCK32;
  }
  if ( (DivMin > 32) && (DivMin < 128) )
  {
    DivMin = 128;
    TimerCounterClockDiv = TC_CLKS_MCK128;
  }
  if ( (DivMin > 128) && (DivMin < 1024) )
  {
    DivMin = 1024;
    TimerCounterClockDiv = TC_CLKS_MCK1024;
  }

  CompareValue = OutputPeriod * (MasterClock/DivMin);
  return ( CompareValue );

}

//*--------------------------------------------------------------------------------------
//* Function Name       : Main
//* Object              : Software entry point
//* Input Parameters    : none.
//* Output Parameters   : none.
//*--------------------------------------------------------------------------------------
int main()
{

  AT91PS_TC pTC1 = AT91C_BASE_TC1;
  unsigned int RcValue = 0;
  unsigned int TioaPeriod = 0;

   /* Enable User Reset and set its minimal assertion to 960 us */
   AT91C_BASE_RSTC->RSTC_RMR = AT91C_RSTC_URSTEN | (0x4<<8) | (unsigned int)(0xA5<<24);

   /********************************************/
   /* TIMER COUNTER 0 CONFIGURATION: Wave Mode */
   /********************************************/
   /* Open PIO for Timer Counter 0 */
   AT91F_TC0_CfgPIO();

   /* Enable TC0's clock in the PMC controller */
   AT91F_TC0_CfgPMC ();

   /* Disable the Clock Counter (within timer counter registers)*/
   *AT91C_TC0_CCR = AT91C_TC_CLKDIS ;

   /* The computed value must be divided by 2 since we are only using RC compare to
   generate the signal*/
   RcValue = (AT91F_TimerCounter_ComputeCompareValue (AT91B_MCK, OUTPUT_FREQ)/2) ;

   /* Initialization of the TC0 to generate a signal via RC register */
   *AT91C_TC0_CMR = (AT91C_TC_WAVE         |      /* Timer Counter in WAVE MODE */
                      TimerCounterClockDiv |      /* TCCLKS computed from AT91F_TimerCounter_ComputeCompareValue  */
                      AT91C_TC_CPCTRG       |     /* CPCTRG  : Register C compare trigger enable */
                      AT91C_TC_ACPC_TOGGLE  |     /* ACPC    : Register C compare toggle TIOA */
                      AT91C_TC_EEVT_XC0     );    /* EEVT    : XC0 as external event (TIOB = output) */

   /* Initialize the RC Compare Reg. to generate 1MHz signal. */
   *AT91C_TC0_RC = RcValue ;


   /* Enable the Clock counter (within timer counter registers) */
   *AT91C_TC0_CCR = AT91C_TC_CLKEN ;

   /* Start timer0 */
   AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG ;

   /***********************************************/
   /* TIMER COUNTER 1 CONFIGURATION: Capture Mode */
   /***********************************************/
   /* Set PIO pins for Timer Counter 1 */
   AT91F_TC1_CfgPIO();
   /* Enable TC1's clock in the PMC controller */
   AT91F_TC1_CfgPMC ();

   /* Measure the period: TioaPeriod will contain the number of the Timer Counter Clock Cycle */
   TioaPeriod = AT91F_TimerCounter_MeasureTioaPeriod (pTC1, AT91C_ID_TC1, MEAS_TIOA_PERIOD);

   /* Suppress warning variable "TioaPeriod" was set but never used */
   TioaPeriod = TioaPeriod ;

    for (;;);
}