Comparator

This example implements the timing function using the RTC Comparator.

When the RTC timer expires, the RTC comparator interrupt is triggered.

Requirements

The sample supports the following development kits:

Development Kits
Hardware Platforms	Board Name
RTL87x2G HDK	RTL87x2G EVB

For more requirements, please refer to Quick Start.

Building and Downloading

This sample can be found in the SDK folder:

Keil

Project file: samples\peripheral\rtc\comparator\proj\rtl87x2g\mdk

GCC

Project file: samples\peripheral\rtc\comparator\proj\rtl87x2g\gcc

To build and run the sample, follow the steps listed below:

Open sample project file.
To build the target, follow the steps listed on the Generating App Image in Quick Start.
After a successful compilation, the app bin app_MP_xxx.bin will be generated in the directory mdk\bin or gcc\bin.
To download app bin into EVB board, follow the steps listed on the MP Tool Download in Quick Start.
Press reset button on EVB board and it will start running.

Experimental Verification

When the comparator setting time (1s) arrives, it triggers the interrupt and prints the interrupt message with a count value of +10 each time.

RTC_Handler: RTC_COMP_INDEX1
RTC_Handler: RTC counter current value = 10
RTC_Handler: RTC_COMP_INDEX1
RTC_Handler: RTC counter current value = 20
...

Code Overview

This chapter will be introduced according to the following several parts:

Source Code Directory.
Peripheral initialization will be introduced in chapter Initialization .
Functional implementation after initialization will be introduced in chapter Functional Implementation .

Source Code Directory

Project Directory: sdk\samples\peripheral\rtc\comparator\proj
Source Code Directory: sdk\samples\peripheral\rtc\comparator\src

Source files are currently categorized into several groups as below.

└── Project: comparator
    └── secure_only_app
        └── Device                   includes startup code
            ├── startup_rtl.c
            └── system_rtl.c
        ├── CMSIS                    includes CMSIS header files
        ├── CMSE Library             Non-secure callable lib
        ├── Lib                      includes all binary symbol files that user application is built on
            └── rtl87x2g_io.lib
        ├── Peripheral               includes all peripheral drivers and module code used by the application
            ├── rtl_rcc.c
            ├── rtl_pinmux.c
            ├── rtl_nvic.c
            └── rtl_rtc.c
        └── APP                      includes the ble_peripheral user application implementation
            ├── main_ns.c
            └── io_rtc.c

Initialization

The initialization process includes driver_rtc_init .

:cpp:any:`driver_rtc_init() contains the initialization of the RTC peripheral.

Deinitialize the RTC peripheral.
Set the RTC prescaler to (3200-1), RTC clock frequency is 10Hz (32K/3200).
Set the comparison value of Comparator channel 1 to 10.
Enable the RTC comparator interrupt RTC_COMP_INDEX_INT.
Reset the RTC count value.
Enable the RTC peripheral.

RTC_DeInit();
RTC_SetPrescaler(RTC_PRESCALER_VALUE);
RTC_SetCompValue(RTC_COMP_INDEX, RTC_COMP_VALUE);
RTC_INTConfig(RTC_COMP_INDEX_INT, ENABLE);
...
RTC_NvCmd(ENABLE);
RTC_ResetCounter();
RTC_Cmd(ENABLE);

Functional Implementation

When the comparator setting time (0.1s * 10 = 1s) is reached, it triggers an RTC interrupt and enters the interrupt handling function RTC_Handler.
1. Print the interrupt message and comparison value message.
2. Reset the comparison value.
3. Clear the RTC comparator channel 1 interrupt.

DBG_DIRECT("RTC_Handler: RTC_COMP_INDEX%d", RTC_COMP_INDEX);
DBG_DIRECT("RTC_Handler: RTC counter current value = %d", RTC_GetCounter());
RTC_SetCompValue(RTC_COMP_INDEX, RTC_GetCounter() + RTC_COMP_VALUE);
RTC_ClearCompINT(RTC_COMP_INDEX);