Temporarily disabling the USART pins (RX and TX) in low power mode, STM32U5

[ASavi.3]

Hi,

I have my PCB that have a processor used as host and STM32U5 (STM32U585AII6Q) used as low power MCU. USART connection is between host and STM32U5.

When I enter Stop3 low power mode, and host is turned off, there is a problem with current on USART RX and TX pins, and that increase power consumption on STM32U5. But, when I, before entering stop mode, set RX and TX USART pins as input analog pins, there is no additional power consumption, but I can't use USART after waking up from low power mode.

Does it exist some way to temporarily disable USART pins (while U5 is in stop mode) for lower power consumption and after waking up to enable RX and TX pins?

Best regards,

Ana Savic

[Tesla DeLorean]

Doesn't the UART have enable bits in the control registers for the UART itself, and the RX and TX individually

Which pin is actually the most responsible for the current, the RX or TX ?

[Bob S]

Are you leaving the UART configured and "running" (RX enabled) as you enter sleep? Or do you disable it, go to sleep, then re-enable it after waking up?

I don't know about the U5, but on other STM32 families when you change a pin to "analog input", the digital path from that pin is forced to zero. If the UART is still attempting to receive data, it will see a "break" condition (may get reported as framing error and/or as "break" - again, I don't know the U5).