Watchdog reconfiguration

[Moufti]

The "5.3.6.8 Reset behavior" table in nRF52840 Product Specification v1.1 mentions that WDT reset does reset the WDT itself.

I'm trying to reconfigure the WDT after a WDT reset but it seems the reload_value is not updated.

Watchdog::Watchdog()

{

#ifndef DISABLE_WATCHDOG

    // Configure WDT.

    nrfx_wdt_config_t config;

    config.behaviour = WDT_CONFIG_BEHAVIOUR;

    config.interrupt_priority = WDT_CONFIG_IRQ_PRIORITY;

    config.reload_value = TIMEOUT_MS;

    uint32_t err_code = nrfx_wdt_init(&config, wdt_event_handler);

    APP_ERROR_CHECK(err_code);

    for (unsigned int i=0; i<MAX_CHANNELS; i++) {

        nrfx_wdt_channel_id id;

        uint32_t err_code = nrfx_wdt_channel_alloc(&id);

        APP_ERROR_CHECK(err_code);

        m_channelIds[i] = id;

        m_assignedChannel[i] = false;

    }

#endif

}

[Moufti]

Seems the max value that can be set is around 130 seconds (the timer overflows beyond that)

[Simonr]

Hi

What SDK version are you using? There was a bug in SDKs before SDK v.16.0.0 where reload values above 131 seconds will not work due to a calculation overflowing internally in the driver during multiplication.

The fix is to replace this line with the following three:

-    nrf_wdt_reload_value_set((p_config->reload_value * 32768) / 1000);

+    uint64_t ticks = (p_config->reload_value * 32768ULL) / 1000;
+    NRFX_ASSERT(ticks <= UINT32_MAX);

+    nrf_wdt_reload_value_set((uint32_t) ticks);

Best regards,

Simon