This is Horrible experance! It's taken me an hour just to get this far. I can't find anyone to call on this question. The number they have for support is out of service, and any atempt to find a number to call just sends back to the number.

[MPoll.961]

If anyone has a working support number would be a big help.  My Question is on the STM32F411 the data sheets state many of the lines are FT 5 volt t​olerant, other team members don't believe this and want to use level shifters, they believe as many lines that we have are 5v and will over load the micro.

[S.Ma]

5V tolerant pin means you can use it as 5v digital input.

If you want output, then it will be with external 5v pull up resistor as open drain.

Typically, pin with analog function will not be 5v tolerant.

Were you expecting 5v push pull output while the Mcu lacks of 5v supply pin?

[MPoll.961]

​Hey thanks much for the quick response, we want to use all 3 I2C lines, all 5v FT, and many I/O lines.  In my option this should be ok, but there are concerns with so many being 5v that it will be to much of a load on the micro.  We could just use a series resistor for a voltage drop and that should work also.

[Tesla DeLorean]

The person you call is typically the distributor's FAE, or ST's FAE, or someone in the sales path that services your account who can gate access to the appropriate people.

The classic problem is that by putting 5V on the IO pins is that it back-feeds into the power ring via the ESD clamping diodes, thus powering the device and driving VDD higher for everything. Here ST has another diode, or diodes, in the path back to 3.3V so you can't do that. I don't think having multiple pins factors into this, it doesn't increase the voltage level, just the sources of current, and as the diodes block that flow, I'm not seeing it as being an issue.

As previously noted the analogue pins are usually outside the FT protection, and older F1 devices had more pins not covered.

[S.Ma]

The STM32 documentation is too precise for its own good.

This is probably why post like this is rare on this forum.

In the datasheet you will get the maximum current you can move through the power supply pins.

If it's open drain, you get switches to ground only. It is usually in 100mA+ do the homework proper to check if you app is compliant. That's any 3.3V MCU specs to analyse proper.

I usually put 10kOhm pull-ups which at 5V will make 1 mA on the ground. peanuts.

I2C bus is open drain, so it should work fine,

[MPoll.961]

​Hey Thanks to you all for the nice Feedback is very helpful!

[BRYAN SPEED]

Personally IMHO, level shifters are good engineering practice. I'm no expert even after 30+ years lol!

[BRYAN SPEED]

support number is working. We are first level of contact.

I am the only one here who has even used/coded I2C.

99% of the time for MCU related, you have to submit an online support request.

and 99% of the time those requests will go directly to MCU support.

And as you can see there are some really smart guys here on the community forum.

[S.Ma]

The series resistor will make the digital 0 lift from ground, when its value becomes too high, reading data will be corrupted.