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I cant figure out the logic shifter

Topic Type: 

I can not seem to find information on what logic shifter to buy. I found an 8-bit shifter on adafruit, is that the right one for this project?

Louis's picture

Thanks for bringing this up. The component [you mention](https://www.adafruit.com/products/735) is the same that I used and it will do the trick! I edited the tool page to include this.

claytonrcarter's picture

I bought the TI level shifter you linked to at AdaFruit and wired it up as directed but couldn't get it to work ... until I realized that the diagrams you have on the "Building on the Shield" page refer to a different shifter with a different pin count and layout. I went back and rewired it according to the instructions on the AdaFruit page and the datasheet and got it to work.

It's a little more complicated then you've drawn up, but here's what I ended up with:

Connect 3.3V to shifter pins 1 and 20. Connect/link shifter pins 10 and 19. Arduino GND and cell phone GND to shifter pin 10. Arduino pin 6 to shifter pin 2. Arduino pin 5 to cell phone Rx. Shifter pin 18 to cell phone Tx.

Also, not sure it's pertinent or not, but the phone I bought had some old texts left on it and the GSMSerial example would NOT work (spit out bogus info) until I cleared them all. As soon as I did, though, it started working perfectly.