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108 lines
2.6 KiB
C
108 lines
2.6 KiB
C
/*
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%atmel_license%
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*/
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/** \addtogroup rtt_module Working with RTT
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* The RTT driver provides the interface to configure and use the RTT
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* peripheral.
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*
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* The Real-time Timer is used to count elapsed seconds.\n
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* This timer is clocked by the 32kHz system clock divided by a programmable
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* 16-bit balue. To be accurate, it is better to use an
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* external 32kHz crystal instead of the internal 32kHz RC.\n
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*
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* To count elapsed seconds, the user could follow these few steps:
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* <ul>
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* <li>Programming PTPRES in RTT_MR to feeding the timer with a 1Hz signal.</li>
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* <li>Writing the bit RTTRST in RTT_MR to restart the timer with new settings.</li>
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* </ul>
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*
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* An alarm can be set to happen on second by setting alarm value in RTT_AR.
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* Alarm occurence can be detected by polling or interrupt.
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*
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* For more accurate information, please look at the RTT section of the
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* Datasheet.
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*
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* Related files :\n
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* \ref rtt.c\n
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* \ref rtt.h.\n
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*/
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/*@{*/
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/*@}*/
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/**
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* \file
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*
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* Implementation of Real Time Timer (RTT) controller.
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*
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*/
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/*----------------------------------------------------------------------------
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* Headers
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*----------------------------------------------------------------------------*/
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#include "chip.h"
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#include <assert.h>
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/*----------------------------------------------------------------------------
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* Exported functions
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*----------------------------------------------------------------------------*/
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/**
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* \brief Changes the prescaler value of the given RTT and restarts it.
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*
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* \note This function disables RTT interrupt sources.
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*
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* \param rtt Pointer to a Rtt instance.
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* \param prescaler Prescaler value for the RTT.
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*/
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void RTT_SetPrescaler(Rtt *rtt, uint16_t prescaler)
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{
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rtt->RTT_MR = (prescaler | RTT_MR_RTTRST);
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}
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/**
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* \brief Returns the current value of the RTT timer value.
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*
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* \param rtt Pointer to a Rtt instance.
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*/
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uint32_t RTT_GetTime(Rtt *rtt)
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{
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return rtt->RTT_VR;
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}
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/**
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* \brief Enables the specified RTT interrupt sources.
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*
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* \param rtt Pointer to a Rtt instance.
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* \param sources Bitmask of interrupts to enable.
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*/
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void RTT_EnableIT(Rtt *rtt, uint32_t sources)
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{
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assert( (sources & 0x0004FFFF) == 0 ) ;
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rtt->RTT_MR |= sources;
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}
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/**
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* \brief Returns the status register value of the given RTT.
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*
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* \param rtt Pointer to an Rtt instance.
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*/
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uint32_t RTT_GetStatus(Rtt *rtt)
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{
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return rtt->RTT_SR;
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}
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/**
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* \brief Configures the RTT to generate an alarm at the given time.
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*
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* \param pRtt Pointer to an Rtt instance.
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* \param time Alarm time.
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*/
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void RTT_SetAlarm(Rtt *pRtt, uint32_t time)
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{
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assert(time > 0);
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pRtt->RTT_AR = time - 1;
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}
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