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Vddio2 usage questions

Question asked by glaser.ralf on Oct 15, 2014
Latest reply on Oct 20, 2014 by glaser.ralf
Hello,

i've an application where an STM32F072 is connected to a GSM engine which provides an I/O voltage when turned on and expects no current flow over the I/O lines into the engine when off. Using Vddio2 for this purpose seems to be the right solution here.

Questions:
1. Is there any possibility to detect whether or not a voltage is applied to Vddio2?
According to the datasheet  Vddio2 is connected to a comparator which generates an internal EXTI interrupt but AFAIK this can only be used to wake up the processor from sleep when a voltage is applied. Is it somehow possible to access the comparator output directly?
2. The datasheet also tells me that when Vddio2 is disconnected the hardware puts the I/O lines in analog input mode. Does this also change the corresponding registers? What happens when Vddio2 is (re-)applied? Do i have to (re-)initialize the I/O lines?
3. In case i wanted to use the comparator are there any other prerequisites than setting up the EXTI interrupt e.g. turning on the internal reference voltage?

Thanks and best regards,
Ralf

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