Problems using RTC_SetCounter

[francesc]

Posted on April 01, 2009 at 10:18

Problems using RTC_SetCounter

[francesc]

Posted on May 17, 2011 at 13:08

Hi.

I have used an RTC sample in my program. When I want to program the counter (set time) with the function RTC_SetCounter, I use the function RTC_WaitForLastTask before and after writing to the counter. Some times the program remains blocked in the second RTC_WatiForLastTask. I have found that in this case the 1 second interruption enters each 4 or 5 micro seconds. Any one know what can be the problem? Thanks for you time

[briand.myers9]

Posted on May 17, 2011 at 13:08Seen this. My guess is that your LSE (low speed external) crystal has too high a capacitance - a very common crystal capacitance is 12.5 pF, and using this crystal will cause the problem you describe. From the datasheet : ''To avoid exceeding the maximum value of CL1 and CL2 (15 pF) it is strongly recommended to use a resonator with a load capacitance CL ≤ 7 pF. Never use a resonator with a load capacitance of 12.5 pF.''

[francesc]

Posted on May 17, 2011 at 13:08

I have been making several test, and I have found that the problem is when I also call the function SetDate. The contents of the function is:

void SetDate(u8 u8_Day, u8 u8_Month, u16 u16_Year) { u32 u32_DateTimer; /* Allow access to BKP Domain */ PWR_BackupAccessCmd(ENABLE); BKP_WriteBackupRegister(BKP_DR2,u8_Month); BKP_WriteBackupRegister(BKP_DR3,u8_Day); BKP_WriteBackupRegister(BKP_DR4,u16_Year); /* Disable access to BKP Domain */ PWR_BackupAccessCmd(DISABLE); } Some one have any idea of why writing to the backup registers I have problems with the RTC?

[francesc]

Posted on May 17, 2011 at 13:08

Thanks for your information.

I use an evaluation board from ST (STM3210E-EVAL), so I think that the crystal should be a correct one. I am looking for possible causes that, after writing an order to the RTC, makes that when calling to RTC_WaitForLastTask, it remains blocked forever. In my project I use the following peripherals: TIM2 to generate an IRQ every 1 mseg, SysTick to generate an IRQ every 10 mSeg, some Outputs ports to control LEDs, and the FSMC to control the LCD.

[francesc]

Posted on May 17, 2011 at 13:08

Hi

Finally I have solve the problem. In the SetDate routine I called PWR_BackupAccessCmd(DISABLE), and after that, I was not able to accede to the RTC. I haven't in mind that the PWR_BackupAccessCmd(DISABLE) also disables the access to the RTC. :D

[francesc]

Posted on May 17, 2011 at 13:08

Hi.

I have reduced the SetDate routine to: PWR_BackupAccessCmd(ENABLE); PWR_BackupAccessCmd(DISABLE); As a summary, the problem is the following. I have a program that: * Uses the 1 second interruption from the RTC. It reads the RTC counter, updates the date if the RTC counter is equal to 86399 and activates a flag to indicate that the main program can display date and time. * Displays the date and time every second. * If I activate a flag, with the debugger, I read de RTC counter and the backup registers for the date, I write again the RTC counter and I write the backup registers for the date (at this moment I don't write to those registers, I only enable and disable de backup access). Some times when I activate the flag to set date and time the program remains blocked in RTC_WaitForLastTask(), and the 1 second interruption enters every 2 o 3 microseconds. It seems that the 1 second interruptions enters continuously leaving the RTC blocked. The RTC_PRL register remains with the correct value. Any idea?