UM0851 datasheet(42/245 Pages) STMICROELECTRONICS

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Platform section

UM0851

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Doc ID 16604 Rev 2

fd = open("/dev/rtc", O_RDONLY, 0);

ret = ioctl(fd, RTC_ALM_SET, &rtc_tm);

/* call the read function to wait the Alarm interrupt */

ret = read(fd, &data, sizeof(unsigned long));

...

close(fd);

Closing the device

The close function is used to disconnect the RTC device with the relevant file descriptor.

int fd;

fd = open("/dev/rtc", O_RDONLY, 0);

...

close(fd);

3.3.3

RTC driver usage

●

hwclock

hwclock is a shell utility for accessing the RTC clock. You can use it to display the

current time, set the hardware clock to a specified time, set the hardware clock to the

system time, and set the system time from the hardware clock. You can also run

hwclock periodically to insert or remove time from the hardware clock in order to

compensate for systematic drift (where the clock consistently gains or loses time at a

certain rate if left to run).

Example:

#hwclock --set --date="9/22/96 16:45:05"

●

rtcwake

rtcwakeup is a shell utility which can be used to program RTC for the next alarm

interrupt. It accepts an argument in seconds, which is the programmed alarm time.

Example:

#rtcwake -s 10

Configuration options

3.3.4

References

●

Refer linux-2.6.27/Documentation/timers/, for the time keeping and tick generation

architecture of Linux.

Table 14.

RTC menuconfig kernel options

Configuration option

Comment

CONFIG_RTC

This option enables the RTC driver.

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