Unused UART Rx pin on STM32F

[krishr]

Dear All,

on my STM32F board, i have the uart rx pin not connected/floating. Due to too many noise interrupts, I have configured UART in tx mode only and disabled RX interrupts. Is this fine? Or should the internal pull up be enabled for the RX pin? 

[SofLit · Accepted solution]

Hello,

Simply configure UART in Tx mode only and keep the Rx pin in default state: don't configure the alternate function on this pin.

[krishr]

Another question - does it have any impact on the current consumption? Does the TX mode only enable pullups for RX  by default?

[SofLit]

The pull-up/down resistors are managed at GPIO peripheral level not the peripheral.

To avoid extra I/O current, the pin should be configured as analog input (AIN). In this mode the Schmitt trigger input is disabled, providing zero consumption for the I/O pin.

[krishr]

Thank you. Could you also explain the difference in current when enabling pull up or configuring in HiZ mode? 

[SofLit]

Hello,

I propose you to open a new thread as this is a different topic.

Thank you.