Software watchdog library (libswdg)

Software multichannel watchdog implementation.

Contents

• Application interface
• Data types
• Functions
• Notes
• Using libswdg

Application interface

Data types

• swdg_callback_t - Callback function to be provided to be executed in the event of channel timeout. channel param conveys information which channel timeout has occurred, this allows one callback to be used for all channels.

typedef void (*swdg_callback_t)(int channel);

Functions

• swdg_reload - Reloads selected watchdog channel no timer. This causes channel deadline to be set to value set in configuration.

void swdg_reload(int no);

• swdg_disable - Disables selected watchdog channel no timer. Configuration is kept, so channel can be re-enabled without additional steps.

void swdg_disable(int no);

• swdg_enable - Enables selected watchdog channel no timer. Channel is refreshed on enable, so no spurious timeout can occur.

void swdg_enable(int no);

• swdg_chanConfig - Configures selected watchdog channel no with desired callback function and limit (in microseconds) deadline.

void swdg_chanConfig(int no, swdg_callback_t callback, time_t limit);

• swdg_init - Initialize library with chanCount channels and watchdog thread with priority priority. Needs to be called before any other operation. chanCount has to be greater than zero, priority has to be greater or equal to zero (the highest priority) and less than 7.

void swdg_init(size_t chanCount, int priority);

Notes

• All channels start disabled,
• Channel configuration does not change its state, channel needs to be enabled if it was not prior,
• Callback function must not call any libswdg functions! Deadlock will occur.

Using libswdg

Normal usage example - one channel active with 30 seconds timeout.

void callback(int no)
{
    systemReboot();
}

int main()
{
    swdg_init(1, 3);
    swdg_chanConfig(0, callback, 30 * 1000 * 1000);
    swdg_enable(0);

    while (1) {
        doAppStuff();
        swdg_reaload(0);
    }

    return 0;
}

Should doAppStuff() function hang/crash for more than 30 seconds, the system will reset.