Example Summary

This application demonstrates how to use the Watchdog driver.

Peripherals & Pin Assignments

When this project is built, the SysConfig tool will generate the TI-Driver configurations into the ti_drivers_config.c and ti_drivers_config.h files. Information on pins and resources used is present in both generated files. Additionally, the System Configuration file (*.syscfg) present in the project may be opened with SysConfig’s graphical user interface to determine pins and resources used.

• CONFIG_GPIO_LED_0 - Indicator LED.
• CONFIG_GPIO_BUTTON_0 - Used to control the application.
• CONFIG_WATCHDOG_0 - Watchdog driver instance.

BoosterPacks, Board Resources & Jumper Settings

For board specific jumper settings, resources and BoosterPack modifications, refer to the Board.html file.

If you’re using an IDE such as Code Composer Studio (CCS) or IAR, please refer to Board.html in your project directory for resources used and board-specific jumper settings.

The Board.html can also be found in your SDK installation:

<SDK_INSTALL_DIR>/source/ti/boards/<BOARD>

Example Usage

1. After loading the example application to the board, disconnect the device from the debug session. Then physically disconnect the device from power for 5 seconds. Reconnect the device and the application should run automatically. Some devices need to skip this power cycle step as this may cause the example application to fail. These devices should load the example and then disconnect the device from the debug session. The example application will then run automatically.

2. The application turns on CONFIG_GPIO_LED_0 to indicate watchdog driver initialization is complete.

3. CONFIG_GPIO_LED_0 is toggled periodically. With each toggle, the watchdog timer is cleared.

4. Pressing CONFIG_GPIO_BUTTON_0 will enter an interrupt service routine which turns CONFIG_GPIO_LED_0 on and enters an infinite loop.

5. The watchdog expires and the device is reset. For some devices, the application will restart.

Application Design Details

• The application opens a Watchdog driver instance configured to reset (Watchdog_RESET_ON) upon the watchdog timer expiring. After Watchdog_open(), the watchdog timer is running with the reload value specified in the board file.

• The application demonstrates how to configure the reload value at runtime. Not all devices support Watchdog_convertMsToTicks() and Watchdog_setReload(). Watchdog_convertMsToTicks() will return 0 if the APIs are not supported, or if the specified reloadValue is not valid. This example configures the reload value to be the same value used in the board file.

• The application’s mainThread enters an infinite loop which periodically clears the watchdog timer using Watchdog_clear(). Each time the watchdog is cleared, CONFIG_GPIO_LED_0 is toggled.

• Power_disablePolicy() and Power_enablePolicy() are used to disable and enable the power driver respectively. Doing so affects how the device behaves when idle. If the power policy is enabled, the device is allowed to enter a low power state when the CPU is idle. Otherwise, the device will stay awake when the CPU is idle. This demonstrates the watchdog driver’s flexibility in an application regardless of power driver usage.

• Pressing CONFIG_GPIO_BUTTON_0 will cause the application to get stuck in the GPIO callback interrupt service routine (ISR), gpioButtonIsr(). This is intended to simulate the application getting stuck unintentionally.

• The watchdogCallback() is called by some watchdog drivers upon a watchdog timeout event. The watchdog interrupt is a non-maskable interrupt (NMI) on some watchdog drivers and therefore will preempt the gpioButtonIsr(). The other watchdog drivers configure the watchdog interrupt as the highest priority interrupt and will still preempt the gpioButtonIsr(). User’s should refer to the device specific watchdog driver documentation for their device’s behavior. This application’s watchdogCallback() will loop infinitely until the watchdog peripheral issues a device reset.

• When the watchdog peripheral issues a device reset, the behavior is equivalent to the user manually pressing the LaunchPad reset button. Therefore, behavior after a reset is device specific. In most instances, the example application will restart.

FreeRTOS:

• Please view the FreeRTOSConfig.h header file for example configuration information.