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RTC Problem in LPC1768

Hello, I'm having problems with RTC in LPC1768. The RTC is running, but is advancing approx 5 seconds per hour. The electrical circuit is good, with a 20ppm crystal tolerance, and 12,5pf capacitors of load. Tha VBAT is conected in CR1220 lithium battery. I have reviewed the source code and is OK. Below is my code:

void InitRTC(void) {
  LPC_RTC->CCR  =    ( !CLKEN |  CTCRST );
  LPC_RTC->CCR &= ~CTCRST;
  return;
}
/***************************/
void StartRTC(void){
  LPC_RTC->CCR |=    ( CLKEN );
  return;
}
/***************************/
int main (void){
  char temp[36];
  InitRTC();
  StartRTC();
  while(1){
    sprintf ((char *)temp,"%2.2d/%2.2d/%.2d   %2.2d:%2.2d",LPC_RTC->DOM,LPC_RTC->MONTH,LPC_RTC->YEAR,LPC_RTC->HOUR,LPC_RTC->MIN);
    lcd_gotoxy(1,0);
    lcd_print(temp);
  }
  return 0;
}

The RTC is running correctly without the battery, with main power connected in VBAT. But yet the RTC is running advancing. I can't use the calibration of application note AN10849. I have 100 identical hardwares, and they are with different accurate. I think that this variation is very high for be simply a low accuracy of LPC. There must be some other problem.

Does anyone know what might be happening?
Thanks

Parents

0 John Linq over 12 years ago in reply to John Linq

lpc17xx.cmsis.driver.library.zip

/********************************************************************//**
 * @brief               Initializes the RTC peripheral.
 * @param[in]   RTCx    RTC peripheral selected, should be LPC_RTC
 * @return              None
 *********************************************************************/
void RTC_Init (LPC_RTC_TypeDef *RTCx)
{
        CHECK_PARAM(PARAM_RTCx(RTCx));

        /* Set up clock and power for RTC module */
        CLKPWR_ConfigPPWR (CLKPWR_PCONP_PCRTC, ENABLE);

        // Clear all register to be default
        RTCx->ILR = 0x00;
        RTCx->CCR = 0x00;
        RTCx->CIIR = 0x00;
        RTCx->AMR = 0xFF;
        RTCx->CALIBRATION = 0x00;
}

/*********************************************************************//**
 * @brief               Enable/Disable calibration counter in RTC peripheral
 * @param[in]   RTCx    RTC peripheral selected, should be LPC_RTC
 * @param[in]   NewState New State of this function, should be:
 *                              - ENABLE: The calibration counter is enabled and counting
 *                              - DISABLE: The calibration counter is disabled and reset to zero
 * @return              None
 **********************************************************************/
void RTC_CalibCounterCmd(LPC_RTC_TypeDef *RTCx, FunctionalState NewState)
{
        CHECK_PARAM(PARAM_RTCx(RTCx));
        CHECK_PARAM(PARAM_FUNCTIONALSTATE(NewState));

        if (NewState == ENABLE)
        {
                RTCx->CCR &= (~RTC_CCR_CCALEN) & RTC_CCR_BITMASK;
        }
        else
        {
                RTCx->CCR |= RTC_CCR_CCALEN;
        }
}

/*-------------------------MAIN FUNCTION------------------------------*/
/*********************************************************************//**
 * @brief               c_entry: Main RTC program body
 * @param[in]   None
 * @return              int
 **********************************************************************/
int c_entry(void)
{
[DELETED]
    /* Enable rtc (starts increase the tick counter and second counter register) */
    RTC_ResetClockTickCounter(LPC_RTC);
    RTC_Cmd(LPC_RTC, ENABLE);
    RTC_CalibCounterCmd(LPC_RTC, DISABLE);
[DELETED]

Reply

0 John Linq over 12 years ago in reply to John Linq

lpc17xx.cmsis.driver.library.zip

/********************************************************************//**
 * @brief               Initializes the RTC peripheral.
 * @param[in]   RTCx    RTC peripheral selected, should be LPC_RTC
 * @return              None
 *********************************************************************/
void RTC_Init (LPC_RTC_TypeDef *RTCx)
{
        CHECK_PARAM(PARAM_RTCx(RTCx));

        /* Set up clock and power for RTC module */
        CLKPWR_ConfigPPWR (CLKPWR_PCONP_PCRTC, ENABLE);

        // Clear all register to be default
        RTCx->ILR = 0x00;
        RTCx->CCR = 0x00;
        RTCx->CIIR = 0x00;
        RTCx->AMR = 0xFF;
        RTCx->CALIBRATION = 0x00;
}

/*********************************************************************//**
 * @brief               Enable/Disable calibration counter in RTC peripheral
 * @param[in]   RTCx    RTC peripheral selected, should be LPC_RTC
 * @param[in]   NewState New State of this function, should be:
 *                              - ENABLE: The calibration counter is enabled and counting
 *                              - DISABLE: The calibration counter is disabled and reset to zero
 * @return              None
 **********************************************************************/
void RTC_CalibCounterCmd(LPC_RTC_TypeDef *RTCx, FunctionalState NewState)
{
        CHECK_PARAM(PARAM_RTCx(RTCx));
        CHECK_PARAM(PARAM_FUNCTIONALSTATE(NewState));

        if (NewState == ENABLE)
        {
                RTCx->CCR &= (~RTC_CCR_CCALEN) & RTC_CCR_BITMASK;
        }
        else
        {
                RTCx->CCR |= RTC_CCR_CCALEN;
        }
}

/*-------------------------MAIN FUNCTION------------------------------*/
/*********************************************************************//**
 * @brief               c_entry: Main RTC program body
 * @param[in]   None
 * @return              int
 **********************************************************************/
int c_entry(void)
{
[DELETED]
    /* Enable rtc (starts increase the tick counter and second counter register) */
    RTC_ResetClockTickCounter(LPC_RTC);
    RTC_Cmd(LPC_RTC, ENABLE);
    RTC_CalibCounterCmd(LPC_RTC, DISABLE);
[DELETED]

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