Pulling 3v3 high to 5v

xanadu

The device attached doesn't care, it has 5v logic anyway. So I'd be pulling a Prop IO pin high to the 5v regulator power using 10k.

Is it okay for the Propeller's IO pin to do this?

Phil Pilgrim (PhiPi)

A 10K pull-up to 5V is okay and will not cause excessive current to flow into the Prop's I/O pin. But it will not pull the pin to 5V; more like 3.9V due to the Prop's internal protection diodes.

xanadu

Thanks Phil. I'm working with the Prop Mini for the first time, no 3.3v pin had me a bit confused.

jmg

Phil Pilgrim (PhiPi) wrote: »

A 10K pull-up to 5V is okay and will not cause excessive current to flow into the Prop's I/O pin. But it will not pull the pin to 5V; more like 3.9V due to the Prop's internal protection diodes.

... and I'll add that you need to ensure either the regulator can sink current, or the Prop current never falls below the sum of all clamping currents, otherwise your 3v3 will climb, and you will fry the Prop.

DigitalBob

You could always use a step up converter to attach your 5 volt sensors. They only cost $3-$4 ready made.

xanadu

Okay, wow. I have located the 3.3v pin on the Prop Mini.

Long day. Thanks everyone!

Clock Loop

Resistor Voltage Divider

Because 3.3V is 2/3 of 5V, it’s easy to create a voltage divider out of resistors.


Also 5v ttl logic only requires 2.7v to make logic high, so leaving 3.3v as the pullup would most likely work fine.