3.3V and 5V Logic Argh!

[divzr0]

Hey guys, maybe a newbie question for some of you but I'm looking for some advice...


I'm using a TI DSP microcontroller that uses 3.3V logic and attempting to use the Parallax PING))) sensor. This particular sensor waits for a 10us high logic from the microcontroller and then takes a distance measurement and reports back a 5V high logic that translates into distance for the amount of time. The parallax sensor uses a single "Signal" pin....

I think I can get away with the microcontroller sending 3.3v but how do I get rectify the 5v down to 3.3 to the microcontoller and still preserve the singal pathway?

Any help?


Thanks!

[Chris Smith]

A simple voltage divider will give you 3.3volts from the 5 volt signal.

[divzr0]

Chris thanks, but I don't think a voltage divider will work....

It works fine coming from the 5V singal of the sensor, but when the dsp microcontoller sends out, its logic is 3.3V so it would divide that further which I would not want.
Any other ideas?

[Chris Smith]

You want to step it up?

Take the lower voltage signal and attach it to a base on a transistor that has a feed of X voltage, that way the smaller voltage gets bigger on the transistor out put side.

[philba]

I'm not familiar with the chip you are using - does it have a bi-directional data line? There are translator designs for that using mosfets. there are also translator chips. here's a decent ap note - http://www.maxim-ic.com/appnotes.cfm/an_pk/1159