STM32F072xx - How to detect VDDIO2 presence?

[MJung.6.279]

DS9826 states that "The VDDIO2 supply is monitored and compared with the internal reference voltage (VREFINT). When the VDDIO2 is below this threshold, all the I/Os supplied from this rail are disabled by hardware. The output of this comparator is connected to EXTI line 31 and it can be used to generate an interrupt."

Is it possible to query directly whether VDDIO2 is below or above threshold? As I understand EXTI 31 can only be configured to trigger on raising or falling edge, but I would just want to read the current output value of the comparator, basically.

Thanks for your help!

[waclawek.jan]

Probably not. You can have a look at SYSCFG_ITLINE1.VDDIO2, but that appears to be just output of the EXTI latch.

JW

[MJung.6.279]

Hi Jan,

thanks for your reply. Unfortunately the SYSCFG_ITLINE1.VDDIO2 seems only to be available only on STM32F09x, but not on the STM32F072xx devices.

Bye, Michael

[waclawek.jan]

Hi Michael,

Why do you think so? I see no such indicated in RM0091.

But regardless, I would be surprised if it would be any different than the respective bit in EXTI pending register's state (i.e. it's just copy of output from EXTI, whereas need to see the input).

Btw., couldn't a pulled-up unconnected input pin within the VDDIO2 ring be used for the required indication?

JW

[MJung.6.279]

Hi Jan,

you are probably right. (The comment about STM32F09x is for SYSCFG_ITLINE0, not for SYSCFG_ITLINE1.) I will give it a try.

> Btw., couldn't a pulled-up unconnected input pin within the VDDIO2 ring be used for the required indication?

That might be an option. Unfortunately for our first PCB version we did not do it. But might be a fall-back for the next revision.

Bye

Michael