According to Android's document of AppWidgetProviderInfo, updatePeriodMillis define how often, in milliseconds, that this AppWidget wants to be updated.
Updates requested with updatePeriodMillis will not be delivered more than once every 30 minutes.
Ref: public int updatePeriodMillis in AppWidgetProviderInfo.
If you want to implement App Widget with higher rate, reference "App Widget using Alarm Manager".
