View Full Version : serial interface

05-03-2006, 10:01 PM
I am trying to interface the basic stamp with a transmitter via a serial.· The device inputs on the transmitter are rated at 3 volts.··Is there a way to·get the I/O pins on the stamp to output at 0-3 volts instead of 5?

Chris Savage
05-03-2006, 10:03 PM

·· Depending on the way the device inputs work you may be able to simply use a 10K resistor.· Or you can use a transistor to interface to the 3V unit.· You would need access to 3V supply for this.

Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

05-05-2006, 01:18 PM
The data sheet for the device sayt that the inputs are CMOS.

Does this sound like a situation where I would need to use a transistor to interface?

05-05-2006, 04:36 PM
Try taking a look at this link - it shows how to convert a transciever signal from 3v-5v and 5v-3v using either transistors or voltage dividers.

I use this method to convert my 3.3v GPS signal, although it was orginally reccomended for some 3.3v Aerocomm transciever modules I have that have pins that are not 5v tolerant.



Post Edited (Robert@HCC) : 5/5/2006 9:39:49 AM GMT

05-05-2006, 11:17 PM

You menetioned that the XCVR that you were using accepted 3.3v TTL signals.· Are there any issues that I need to take into account considering the fact that the XCVR device that I am working with requires that the signals be CMOS compatible?··Also,· is there any significant difference between the transistor circuit and the divider circuit that I should be concerned with?