Hi,
i have to connect a pressure sensor to 3.1v and a shift register to the 5v. Of a teensy 3.2. in the same circuit.
Can I do it directly, or do I need a level converter. I would not prefer to use a level converter.
Thank you.

 

If these are digital signals for use with CMOS you would get most likely get unreliable operation without a level shifter. You can tell for sure by checking the gauranteed minimum high and maximum low input levels of the teensy 3.2 against the gauranteed maximum high and maximum low output levels of the pressure sensor.

 

Details, details, details.
What is the part number of the pressure sensor and shift register?
How are your components connected?
A circuit diagram would help.

 

I am sorry.
I use seven CD 4021b shift register in a daisy chain with hall effect sensor to digitalize an accordion. And a
BMP180 barometric pressure to measure the air there for. The BMP 180, I bought is a china product. Unfortunately without datasheet. My question gose only to power supplying the shift register and BMP 180 from the Teensy. Teensy has both 5v and 3.3v.
I will try to post later a circuit diagram when I get home

 

Now I tried to make a sketch. Sorry for not professional sketch.
My question is, if can use the C1 and C2 connection in this circuit.

 

You can power them like that but the I2C connections will need a bi-directional level shifter.
e.g. http://www.ebay.co.uk/itm/2-5-10X-2...hash=item282f84ce27:m:mTxcKb2rMavh2laUuEhEVcA

 

Sorry I can not understand why do I need the level shifter. I would power each of them with the required power. I expect it should work fine. Or do I think wrong?

 

The I2C from the teensy will be 5V but the BMP180 I2C will be 3.3V. The 5V may damage the BMP180 and/or the 3.3V will not correctly connect to the teensy.

 

The teensy 3.2 runs at 3.3V and the almost all the pins are 5v tolerant.