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TM4C123GH6PM: How to Restore RTC values after power cycle?

Sumit Mourya
Expert 1800 points
Part Number: TM4C123GH6PM


Hello all,

I'am using my own TM4C123GH6PM Custom Board  and I'am trying to implement the RTC of the MCU.

I'am using the 32.768 KHz crystal and connected a 3V Coin cell to the Vbat pin with an RC circuit(51 ohm & 0.1 uF) between VBat and Coin cell.

The code below is written for RTC 

time_t calendar_write;
time_t calendar_read;
struct tm tm1 = {0,15,16,2,3,2018-1900,1,0,0};
struct tm tm2 = {0};



int main()

{



SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_PLL | SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ); // clock at 80 Mhz

ui32SysClkFreq = 80000000;

// Enable the Hibernation module.
SysCtlPeripheralEnable(SYSCTL_PERIPH_HIBERNATE);

// Wait for the Hibernate module to be ready.
while(!SysCtlPeripheralReady(SYSCTL_PERIPH_HIBERNATE))
{
}
HibernateEnableExpClk(ui32SysClkFreq);

//
// Wait an amount of time for the module to power up.
//

// Configure the clock source for Hibernation module and enable the
// RTC feature.
HibernateClockConfig(HIBERNATE_OSC_HIGHDRIVE);
HibernateRTCEnable();

HibernateCounterMode(HIBERNATE_COUNTER_RTC);

calendar_write = umktime(&tm1);

HibernateRTCSet(calendar_write);



while(1)

{

calendar_read = HibernateRTCGet();
ulocaltime(calendar_read, &tm2);

// format the output for uart
strftime((char *)buf_rz, 32, "%c\r\n", &tm2);

}

}

The issue is that I'am not able to restore the hour:minutes:seconds values after power cycle. The RTC resets when I power cycle the board.

  • 0
    Expert 1800 points
    just an update. I was able to solve the problem by changing the logic of my code. I made the user to set the time in my application . Once the time is set , it keeps on running after power off also till the time battery is not removed. just the same way as in mobile phones!
  • 0 in reply to Sumit Mourya
    TI__Guru**** 191906 points
    Hi Sumit,
    Glad your problem is solved. Do you mind to post your updated code so others in the community can also benefit? Thanks.
  • 0 in reply to Charles Tsai
    Expert 1800 points 
    uint32_t XTime;
uint32_t hours;
uint32_t minutes;
uint32_t second;

 void UART3IntHandler(void)
 {
   uint32_t    ui32Status1;

 ui32Status1 = UARTIntStatus(UART3_BASE, true);

  UARTIntClear(UART3_BASE, ui32Status1);

Customhour[g]=UARTCharGet(UART3_BASE);
Custominute[g]=UARTCharGet(UART3_BASE);

hour = atoi(Customhour);
min = atoi(Custominute);
uint32_t total = (min*60) + (hour*3600);             
HibernateRTCSet(total);

}

int main()

{
SysCtlClockSet(SYSCTL_SYSDIV_2_5 | SYSCTL_USE_PLL | SYSCTL_OSC_MAIN | SYSCTL_XTAL_16MHZ); // clock at 80 Mhz

    ui32SysClkFreq = 80000000;

    // Enable the Hibernation module.
    SysCtlPeripheralEnable(SYSCTL_PERIPH_HIBERNATE);

    // Wait for the Hibernate module to be ready.
    while(!SysCtlPeripheralReady(SYSCTL_PERIPH_HIBERNATE))
    {
    }
    HibernateEnableExpClk(ui32SysClkFreq);

    //
    // Wait an amount of time for the module to power up.
    //

    // Configure the clock source for Hibernation module and enable the
    // RTC feature.
    HibernateClockConfig(HIBERNATE_OSC_HIGHDRIVE);
    HibernateRTCEnable();

    HibernateCounterMode(HIBERNATE_COUNTER_RTC);

while(1)
{
XTime = HibernateRTCGet();

        hours = ((XTime /3600)) % 24;
        minutes = ((XTime /60)) % 60;
        second = (XTime % 60);

        usprintf(buf_rz,"%d %d %d",hours,minutes,second);

}
}

    yes sure,. This code requires the application user to set the time . So you probably need a UI in your application.