RTC Usage Guidelines
- How to Use
- Creating an RTC Device Handle
- Releasing the RTC Device Handle
- Registering RtcAlarmCallback
- Performing RTC-related Operations
How to Use
During the OS startup, the HDF loads the RTC driver based on the configuration file. The RTC driver detects the RTC component and initializes the driver.
Figure 1 illustrates the process of an RTC device.
Figure 1 Process of using an RTC device
Creating an RTC Device Handle
After the RTC driver is loaded successfully, you can use the API provided by the HDF and call APIs of the RTC driver.
NOTE: Currently, only one RTC device is supported in the OS.
DevHandle RtcOpen(void);
Table 1 Description of RtcOpen
DevHandle handle = NULL;
/* Obtain the RTC device handle. */
handle = RtcOpen();
if (handle == NULL) {
/* Process the error. */
}
Releasing the RTC Device Handle
You can call the following function to release the RTC device handle, thereby releasing resources of the device:
void RtcClose(DevHandle handle);
Table 2 Description of RtcClose
/* Release the RTC device handle. */
RtcClose(handle);
Registering RtcAlarmCallback
After the OS is started, call the following function to register RtcAlarmCallback, which will be invoked when an alarm is generated at the specified time:
int32_t RtcRegisterAlarmCallback(DevHandle handle, enum RtcAlarmIndex alarmIndex, RtcAlarmCallback cb);
Table 3 Description of RtcRegisterAlarmCallback
Callback that will be invoked when an alarm is generated at the specified time. |
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The following is an example of registering RtcAlarmCallback for processing alarm RTC_ALARM_INDEX_A:
/* Register an RTC alarm callback. */
int32_t RtcAlarmACallback(enum RtcAlarmIndex alarmIndex)
{
if (alarmIndex == RTC_ALARM_INDEX_A) {
/* Process alarm A. */
} else if (alarmIndex == RTC_ALARM_INDEX_B) {
/* Process alarm B. */
} else {
/* Process the error. */
}
return 0;
}
int32_t ret;
/* Register RtcAlarmCallback for alarm A. */
ret = RtcRegisterAlarmCallback(handle, RTC_ALARM_INDEX_A, RtcAlarmACallback);
if (ret != 0) {
/* Process the error. */
}
Performing RTC-related Operations
- Reading RTC time
Call the following function to read time information from the RTC driver, including the year, month, the day fo the week, day, hour, minute, second, and millisecond:
int32_t RtcReadTime(DevHandle handle, struct RtcTime *time);
Table 4 Description of RtcReadTime
Pointer to the time information read from the RTC driver. The time information includes the year, month, the day of the week, day, hour, minute, second, and millisecond. |
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int32_t ret;
struct RtcTime tm;
/* Read time information from the RTC driver. */
ret = RtcReadTime(handle, &tm);
if (ret != 0) {
/* Process the error. */
}
- Setting RTC time
Call the following function to set the RTC time:
int32_t RtcWriteTime(DevHandle handle, struct RtcTime *time);
Table 5 Description of RtcWriteTime
Pointer to the time information written into the RTC driver. The time information includes the year, month, the day of the week, day, hour, minute, second, and millisecond. |
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NOTE: The RTC start time is 1970/01/01 Thursday 00:00:00 (UTC). The maximum value of year must be set based on the requirements specified in the product manual of the in-use component. You do not need to configure the day of the week.
int32_t ret;
struct RtcTime tm;
/* Set the RTC time to UTC 2020/01/01 00:59:00 .000. */
tm.year = 2020;
tm.month = 01;
tm.day = 01;
tm.hour= 00;
tm.minute = 59;
tm.second = 00;
tm.millisecond = 0;
/* Write the RTC time information. */
ret = RtcWriteTime(handle, &tm);
if (ret != 0) {
/* Process the error. */
}
- Reading the RTC alarm time
Call the following function to read the alarm time:
int32_t RtcReadAlarm(DevHandle handle, enum RtcAlarmIndex alarmIndex, struct RtcTime *time);
Table 6 Description of RtcReadAlarm
Pointer to the RTC alarm time information. The time information includes the year, month, the day of the week, day, hour, minute, second, and millisecond. |
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int32_t ret;
struct RtcTime alarmTime;
/* Read the RTC alarm time information of alarm RTC_ALARM_INDEX_A. */
ret = RtcReadAlarm(handle, RTC_ALARM_INDEX_A, &alarmTime);
if (ret != 0) {
/* Process the error. */
}
- Setting RTC alarm time
Call the following function to set the RTC alarm time based on the alarm index:
int32_t RtcWriteAlarm(DevHandle handle, enum RtcAlarmIndex alarmIndex, struct RtcTime *time);
Table 7 Description of RtcWriteAlarm
Pointer to the RTC alarm time information. The time information includes the year, month, the day of the week, day, hour, minute, second, and millisecond. |
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NOTE: The RTC start time is 1970/01/01 Thursday 00:00:00 (UTC). The maximum value of year must be set based on the requirements specified in the product manual of the in-use component. You do not need to configure the day of the week.
int32_t ret;
struct RtcTime alarmTime;
/* Set the RTC alarm time to 2020/01/01 00:59:59 .000. */
alarmTime.year = 2020;
alarmTime.month = 01;
alarmTime.day = 01;
alarmTime.hour = 00;
alarmTime.minute = 59;
alarmTime.second = 59;
alarmTime.millisecond = 0;
/* Set the alarm time of alarm RTC_ALARM_INDEX_A. */
ret = RtcWriteAlarm(handle, RTC_ALARM_INDEX_A, &alarmTime);
if (ret != 0) {
/* Process the error. */
}
- Enabling or disabling alarm interrupts
Before performing alarm operations, use this function to enable alarm interrupts, so that RtcAlarmCallback will be called when the alarm is not generated upon a timeout.
int32_t RtcAlarmInterruptEnable(DevHandle handle, enum RtcAlarmIndex alarmIndex, uint8_t enable);
Table 8 Description of RtcAlarmInterruptEnable
Whether to enable RTC alarm interrupts. Value 1 means to enable alarm interrupts and value 0 means to disable alarm interrupts. |
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int32_t ret;
/* Enable the RTC alarm interrupts. */
ret = RtcAlarmInterruptEnable(handle, RTC_ALARM_INDEX_A, 1);
if (ret != 0) {
/* Process the error. */
}
- Reading RTC external frequency
Call the following function to read the frequency of the external crystal oscillator connected to the RTC driver:
int32_t RtcGetFreq(DevHandle handle, uint32_t *freq);
Table 9 Description of RtcGetFreq
Frequency to set for the external crystal oscillator, in Hz. |
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int32_t ret;
uint32_t freq = 0;
/* Read frequency of the external crystal oscillator connected to the RTC driver */
ret = RtcGetFreq(handle, &freq);
if (ret != 0) {
/* Process the error. */
}
- Setting the frequency of the external crystal oscillator connected to the RTC driver
Call the following function to set the frequency of the external crystal oscillator connected to the RTC driver:
int32_t RtcSetFreq(DevHandle handle, uint32_t freq);
Table 10 Description of RtcSetFreq
Frequency to set for the external crystal oscillator, in Hz. |
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int32_t ret;
uint32_t freq = 32768; /* 32768 Hz */
/* Set the frequency of the external crystal oscillator. Note that the frequency must be configured in accordance with the requirements specified in the product manual of the in-use component. */
ret = RtcSetFreq(handle, freq);
if (ret != 0) {
/* Process the error. */
}
- Resetting the RTC driver
Call the following function to perform a reset on the RTC driver. After the reset, the registers are restored to the default values:
int32_t RtcReset(DevHandle handle);
Table 11 Description of RtcReset
int32_t ret;
/* Reset the RTC driver. After the reset, the configuration registers are restored to the default values. */
ret = RtcReset(handle);
if (ret != 0) {
/* Process the error. */
}
- Reading the configuration of a custom RTC register
Call the following function to read the configuration of a custom RTC register based on the register index (one index corresponds to one byte of the configuration value):
int32_t RtcReadReg(DevHandle handle, uint8_t usrDefIndex, uint8_t *value);
Table 12 Description of RtcReadReg
int32_t ret;
uint8_t usrDefIndex = 0; /* Define index 0 for the first custom register. */
uint8_t value = 0;
/* Read the configuration of a custom RTC register based on the register index. One index corresponds to one byte of the configuration value. */
ret = RtcReadReg(handle, usrDefIndex, &value);
if (ret != 0) {
/* Process the error. */
}
- Setting the configuration of a custom RTC register
Call the following function to configure a register based on the specified register index (one index corresponds to one byte of the configuration value):
int32_t RtcWriteReg(DevHandle handle, uint8_t usrDefIndex, uint8_t value);
Table 13 Description of RtcWriteReg
int32_t ret;
uint8_t usrDefIndex = 0; /* Define index 0 for the first custom register. */
uint8_t value = 0x10;
/* Configure a register based on the specified register index. One index corresponds to one byte of the configuration value. */
ret = RtcWriteReg(handle, usrDefIndex, value);
if (ret != 0) {
/* Process the error. */
}