====================== Watchdog Timer Drivers ====================== NuttX supports a low-level, two-part watchdog timer driver. #. An "upper half", generic driver that provides the common watchdog timer interface to application level code, and #. A "lower half", platform-specific driver that implements the low-level timer controls to implement the watchdog timer functionality. Files supporting the watchdog timer driver can be found in the following locations: - **Interface Definition**. The header file for the NuttX watchdog timer driver reside at ``include/nuttx/timers/watchdog.h``. This header file includes both the application level interface to the watchdog timer driver as well as the interface between the "upper half" and "lower half" drivers. The watchdog timer driver uses a standard character driver framework. - **"Upper Half" Driver**. The generic, "upper half" watchdog timer driver resides at ``drivers/timers/watchdog.c``. - **"Lower Half" Drivers**. Platform-specific watchdog timer drivers reside in ``arch/``\ **\ ``/src/``\ ** directory for the specific processor ** and for the specific ** watchdog timer peripheral devices. There are two ways to enable Watchdog Timer Support along with the Watchdog Example. The first is faster and simpler. Just run the following command to use a ready config file with watchdog timer support and example included. You need to check if there's a watchdog config file for your specific chip. You may check it at the specific board's path: ``/boards////config``. .. code-block:: console $ ./tools/configure.sh :watchdog And the second way is creating your own config file. To do so, follow the next instructions. Enabling the Watchdog Support and Example in ``menuconfing`` ------------------------------------------------------------ 1. Select Watchdog Timer Instances To select these wdts browse in the ``menuconfig`` using the following path: Go into menu :menuselection:`System Type --> Peripheral Selection` and press :kbd:`Enter`. Then select one or more watchdog timers according to availability of your chip. 2. Enable the Watchdog Timer Support Go into menu :menuselection:`Device Drivers --> Timer Driver Support` and press :kbd:`Enter`. Then enable: - [x] Watchdog Timer Support 3. Include the Watchdog Timer Example Go into menu :menuselection:`Application Configuration --> Examples` and press :kbd:`Enter`. Then select the Watchdog Timer example. - [x] Watchdog Timer example Below the option, it is possible to manually configure some standard parameters that will be used by the example, but they also can be passed as command line arguments later. The parameters are the following: the standard timer device path (which defines the WDT instance), the timeout period (which is the period on which the watchdog will expire), the ping delay (which is the interval period between feeding the dog) and the ping time (which is the total interval that the example will feed the dog, after this interval, the dog will starve and the chip will trigger an interrupt or reset. 4. Include the Debug Watchdog Feature In order to get the watchdog timer status, you need to enable it. For production code and for your application you may disable it. Go into menu :menuselection:`Build Setup --> Debug Options` and press :kbd:`Enter`. Then enable: - [x] Enable Debug Features - [x] Watchdog Timer Debug Features Watchdog Timer Example ---------------------- The previously selected example will basically do the following: * Open the watchdog device * Set the watchdog timeout * Start the watchdog timer * Ping (feed the dog) during the ``pingtime`` with a delay of ``pingdelay`` and print out the wdt status in case debug was enabled. * Enter into an endless loop without pinging. It will cause the watchdog timer to reset the chip on timeout, i.e., after timer expiration. The `example code `_ may be explored, its path is at ``/examples/watchdog/watchdog_main.c`` in the apps' repository. In NuttX, the watchdog timer driver is a character driver and when a chip supports multiple watchdog timers, each one is accessible through its respective special file in ``/dev`` directory. Each watchdog timer is registered using a unique numeric identifier (i.e. ``/dev/watchdog0``, ``/dev/watchdog1``, ...). Use the following command to run the example: .. code-block:: console nsh> wdog This command will use the watchdog timer 0. To use the others, specify it through a parameter (where x is the timer number): .. code-block:: console nsh> wdog -i /dev/watchdogx Application Level Interface ---------------------------- The first necessary thing to be done in order to use the watchdog timer driver in an application is to include the header file for the NuttX Watchdog timer driver. It contains the Application Level Interface to the timer driver. To do so, include: .. code-block:: c #include At an application level, the watchdog timer functionalities may be accessed through ``ioctl`` systems calls. These ``ioctl`` commands internally call lower-half layer operations and the parameters are forwarded to these operations through the ``ioctl`` system call. The example provides a great resource to demonstrate how to use those ``ioctl`` commands. The available ``ioctl`` commands are: .. c:macro:: WDIOC_START This command starts the watchdog timer. .. c:macro:: WDIOC_STOP This command stops the watchdog timer. .. c:macro:: WDIOC_GETSTATUS This command gets the status of the watchdog timer. It receives a writeable pointer to struct ``watchdog_status_s`` as parameter. The lower-half driver writes the current status in this struct. .. c:struct:: watchdog_status_s .. code-block:: c struct watchdog_status_s { uint32_t flags; /* See WDFLAGS_* definitions above */ uint32_t timeout; /* The current timeout setting (in milliseconds) */ uint32_t timeleft; /* Time left until the watchdog expiration * (in milliseconds) */ }; .. c:macro:: WDIOC_SETTIMEOUT This command sets the timeout value, i.e., the value that will trigger the reset or interrupt. The argument is a ``uint32_t`` value in miliseconds. .. c:macro:: WDIOC_CAPTURE This command registers an user callback that will be triggered on timeout. It receives as argument a pointer to struct ``watchdog_capture_s``. If the user callback is NULL, then it configures only to reset. Not all chips support interrupt on timeout. This command is optional, i.e., if it's not used, the standard behaviour is to reset on timeout. .. c:struct:: watchdog_capture_s .. code-block:: c struct watchdog_capture_s { CODE xcpt_t newhandler; /* The new watchdog capture handler */ CODE xcpt_t oldhandler; /* The previous watchdog capture handler (if any) */ }; .. c:macro:: WDIOC_KEEPALIVE This command resets the watchdog timer ("ping", "pet the dog", "feed the dog").