Dialog DA14531 — WDT

A watchdog timer (WDT) is used to help the system recover from any anomalies/failures. It is a hardware timer which resets the system when it overflows. The system needs to reset the watchdog timer before it “times out”.

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Project setup

Any of the older projects can be used for this tutorial. They are available on Github at https://github.com/vicara-hq/da14531-tutorials

Hardware overview

We will use a DA145xx Pro motherboard with a DA14531 Tiny module daughterboard.

Code Overview

Out of all the peripherals the DA14531 provides, the WDT is the easiest peripheral to use. The Dialog SDK6 has 2 preprocessor definitions which control the working of the Watchdog Timer. They can be found in the da1458x_basic_config.h file.

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/****************************************************************************************************************/
/* Enables WatchDog timer.                                                                                      */
/****************************************************************************************************************/
#define CFG_WDOG/****************************************************************************************************************/
/* Watchdog timer behavior in production mode:                                                                  */
/*     Flag is not defined: Watchdog timer generates NMI at value 0.                                            */
/*     Flag is defined    : Watchdog timer generates a WDOG (SYS) reset at value 0.                             */
/****************************************************************************************************************/
#undef CFG_WDG_TRIGGER_HW_RESET_IN_PRODUCTION_MODE

When CFG_WDOG is defined, the Watchdog timer is enabled. The pre configured duration for the WDT is 2048 ms which is ~2 seconds.

Note: The configuration files do not provide any options to change the WDT period but it can be changed by modifying WATCHDOG_DEFAULT_PERIOD in arch_wdg.h . I have not tested this change and cannot assure that this will not cause any other problems.

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CFG_WDG_TRIGGER_HW_RESET_IN_PRODUCTION_MODE defines the behaviour of a WDT overflow when the project is built in Production mode i.e. CFG_DEVELOPMENT_DEBUG is undefined. If CFG_WDG_TRIGGER_HW_RESET_IN_PRODUCTION_MODE is defined, it generates a system reset. If it’s not defined, a Non Maskable Interrupt is generated which might store some data related to the fault before triggering a system reset.

If the project is in Debug mode, the execution of the code halts and does not reset. This allows a debugger to be attached and check what has caused the error.

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