5v Tolerant UART on STM32H753

[Yan Rosh]

Posted on May 30, 2018 at 17:08

Hello,

We want to connect a 5v UART device to our STM32H753 MUC through one of the 5v-tolerant UART_RX pins.

The MCU IO voltage is 1.8v.

The UART is one-directional, from the 5v device to a UART_RX pin, for example PB15.

Is there anything we need to take into account here? Is there an internal pull-up/down on pin?

Thanks in advance,

Yan

#uart-rx #5v-tolerant

[T J]

Posted on May 30, 2018 at 17:51

Do you have to use a 5V RS232 device ?

You can use a voltage divider to lower the high voltage,

or use a transistor to level shift  (but it also inverts the input.)

I wonder if the excessive voltage would disturb the analog inputs.  maybe.

[Yan Rosh]

Posted on May 31, 2018 at 09:56

Hi TJ,

Thanks for the reply!

We have to use the 5v device, it goes only as low as 2.7v and we want to power the MCU from 1.8v.

We could use a voltage divider, but do we have to?

We want to save as much space as we can on the board, so any extra components are examined very closely

Thanks,

Yan

[T J]

Posted on May 31, 2018 at 11:57

do you need analog ? probably wont work well with 5v on some pins...

[Yan Rosh]

Posted on May 31, 2018 at 13:13

We won't be using this for the analog pins, just for digital