RTC hal
[Hal]

Deinitialize RTC.

Powerdown the RTC in preparation for sleep, powerdown or reset. That should only affect the CPU domain and not the time keeping logic. After this function is called no other RTC functions should be called except for rtc_init.

Note:

This function does not stop the RTC from counting - Tested by rtc_persist_test

Example Implementation Pseudo Code:

 void rtc_free()
 {
     // Disable clock gate since processor no longer needs to read RTC registers
     POWER_CTRL &= ~POWER_CTRL_RTC_Msk;
 }

Initialize the RTC peripheral.

Powerup the RTC in perpetration for access. This function must be called before any other RTC functions ares called. This does not change the state of the RTC. It just enables access to it.

Note:

This function is safe to call repeatedly - Tested by rtc_init_test

Example Implementation Pseudo Code:

 void rtc_init()
 {
     // Enable clock gate so processor can read RTC registers
     POWER_CTRL |= POWER_CTRL_RTC_Msk;

     // See if the RTC is already setup
     if (!(RTC_STATUS & RTC_STATUS_COUNTING_Msk)) {

         // Setup the RTC clock source
         RTC_CTRL |= RTC_CTRL_CLK32_Msk;
     }
 }

Check if the RTC has the time set and is counting.

Return values:

0	The time reported by the RTC is not valid
1	The time has been set the RTC is counting

Example Implementation Pseudo Code:

 int rtc_isenabled()
 {
     if (RTC_STATUS & RTC_STATUS_COUNTING_Msk) {
         return 1;
     } else {
         return 0;
     }
 }

Get the current time from the RTC peripheral.

Returns:

The current time in seconds

Note:

Some RTCs are not synchronized with the main clock. If this is the case with your RTC then you must read the RTC time in a loop to prevent reading the wrong time due to a glitch. The test rtc_glitch_test is intended to catch this bug.

Example implementation for an unsynchronized ripple counter:

 time_t rtc_read()
 {
     uint32_t val;
     uint32_t last_val;

     // Loop until the same value is read twice
     val = RTC_SECONDS;
     do {
         last_val = val;
         val = RTC_SECONDS;
     } while (last_val != val);

     return (time_t)val;
 }

Write the current time in seconds to the RTC peripheral.

Parameters:

t	The current time to be set in seconds.

Example Implementation Pseudo Code:

 void rtc_write(time_t t)
 {
     RTC_SECONDS = t;
 }