STM32f071RB PA1 Comparator

[tage]

Hello!

I'm using Comparator 1 in the STM32f071rbt6 uC. The Comp  is properly configured, and sends an interrupt once triggered on PA1 referenced to PA4(DAC_OUT_1).

it happened that the PA1 GPIO accidentally was not configured. Yet the comparator functionality still works. Is this somehow possible? As far as I know GPIOs are configured as input float and for the COMP1 it need to be alternative function in order to be connected. Any idea why this works? 

Thanks and have a great day!

[Joe WILLIAMS]

Hello tage

This post has been escalated to the ST Online Support Team for additional assistance.  We'll contact you directly.

Kind Regards

Joe WILLIAMS

STMicro Support

[waclawek.jan]

> As far as I know GPIOs are configured as input float and for the COMP1 it need to be alternative function in order to be connected.

PA1 here is used as COMP1_INP i.e. input. RM requires it to be set as Analog Input:

(COMP *outputs* need to be configured as AF, but that's not the case here.)

However, in 'F0, analog functions such as ADC - and apparently also COMP - which are on TTa pins (as is PA1), are connected directly to given pin. It means, that they work also if the pin is set to GPIO Input; however, their "performance" is influenced by the connected Schmitt trigger input circuit. Setting it to Analog disconnects that circuit.

JW

PS. @Joe WILLIAMS , can you please discuss/correct me here. Thanks.