6 years ago.

5V tolerant pins on Nucleo boards

Hello again, I'm trying to work out which pins on the Nucleo boards are 5V tolerant, I've heard they all are except when doing analog reads but just want to clarify this. I've looked all over the web but haven't found an answer I trust. Thanks Mike

5 Answers

6 years ago.

Take a look also at your MCU reference manual, for example for F411 http://www.st.com/st-web-ui/static/active/en/resource/technical/document/reference_manual/DM00119316.pdf page 143 Tells all the pins marked with FT have this internal scheme /media/uploads/Geremia/gpio.png

There are 2 voltage clamping diodes that limits the voltage on the external pin, whatever the pin function, ADC included. It does not tell the Vdd_ft value, but i suppose whatever applied to ext pin, it will be clamped to 3.3. The F411 datasheet page 60 tells absolute max rating for Vin on FT pins -0.3 to Vdd+4 (Where VDD can be max 4, so 8V), while for std operatin conditions tells Vin -0.3 to 5.5, with the note "To sustain a voltage higher than VDD+0.3, the internal Pull-up and Pull-Down resistors must be disabled". If you set the pin for ADC, pullup/down are disabled.

Accepted Answer
6 years ago.


The best source to trust is the product datasheet that you can find on st.com. In the "pinouts and pin description" chapter you will find all the information you're looking for about the 5V tolerant pins.


6 years ago.

Extracted from Nucleo User Manual: http://www.st.com/st-web-ui/static/active/en/resource/technical/document/user_manual/DM00105823.pdf

"Caution: The IOs of STM32 microcontroller are 3.3 V compatible instead of 5 V for Arduino Uno."

So no 5V on Nucleo boards.

6 years ago.

That's interesting because the Datasheet for the Processor used on the Nucleo-411RE is an STM32F411RET6 and the datasheet for that processor says "All I/O ports are 5 V-tolerant"


I would check the datasheet for the specific processor and trust that data.

So I did a bit more research using the links you gave me and there is a table in the mouser DM001 document which lists all the FT (5V tolerant ) and TC (3.3 V ) pins -and there are some labeled TC but I've yet to work out what they are, although on page 1 it does state that : "-Up to 77 5 V-tolerant I/Os – A ll I/O ports are 5 V-tolerant" . As to the question of analog pins the only reference I found was in AN2834 "How to get the best ADC accuracy in STM32Fx Series and STM32L1 Series devices" where the Vref is always 3.3 V and this implies that the maximum voltage cannot be higher than this. I wouldv'e thought that with so many programs being written and projects built that this wouldv'e been sorted out by now.

Cheers Mike

posted by Michael Bawden 01 Oct 2014


Page 46 of that DM001 document has a note on the FT 5V-tolerant pins: "4. FT = 5 V tolerant except when in analog mode or oscillator mode (for PC14, PC15, PH0 and PH1)."


posted by Corey Jurkovich 01 Oct 2014
6 years ago.

Pin set to Digital Out and High State measured at 3.3V with Multimeter. (Nucleo F411RE)

But i think that with the term 5V tolerant, manufacturer means that the GPIOs can tolerate INPUT Voltage of 5V, reading it as HIGH STATE, without being damaged (as long as IO current is within the specifications =20mA). I may be wrong. Correct me if so. Regards.

posted by Manos Kav 01 Oct 2014

I think you are spot on Manos!

tol·er·ant - /ˈtälərənt/ adjective adjective: tolerant

1. showing willingness to allow the existence of opinions (5V) or behavior that one (3.3V) does not necessarily agree with.


posted by Corey Jurkovich 01 Oct 2014