STM32F0 wake up from standby by multiple pins

[Slavomir Simko]

Posted on August 18, 2017 at 13:33

Hello,

I have an issue when trying to exit from standby power mode on the STM32F091CB MCU.

I want to use 3 wake up pins (EWUP1, EWUP2, EWUP7 set in PWR_CSR register).

One of this pins (EWUP2) is already high when entering standby (waiting for next rising edge). Regarding the note in RM0091 reference manual I know that additional wakeup event is detected and the WUF is being cleared before entering the standby.

The problem is that MCU wont leave the standby from other pins than EWUP2. However, if I configure only EWUP1, EWUP7 which are in low by default, there is no problem to wake up by them. So, I suspect that issue is in the case of combination with pin, which is already in high state...

Thank you for any suggestions.

[waclawek.jan]

Posted on August 21, 2017 at 19:37

Read the 'Wakeup sequence from Standby mode when using more than one wakeup source' erratum:

The various wakeup sources are logically OR-ed in front of the rising-edge detector which

generates the wakeup flag (WUF). [...]

In other words, 'waiting for the next leading edge' won't work; you need to redesign your circuitry so that all wakeup sources are low when going into standby.

JW

[Slavomir Simko]

Posted on August 22, 2017 at 08:04

Thank you.

Yes, I found this 'limitation' described.