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Topic: Xbee and Wireless shields: 3.3V-5V level translating problem (Read 735 times) previous topic - next topic

prairiemystic

I bought an XBee shield V03 from geeetech.com and ran into a shield design problem while checking it out- before installing my Xbee module :)
It's the same circuit as http://arduino.cc/en/Main/ArduinoXbeeShield

The Xbee modules are 3.3V and my Uno is 5V. For level translation there is a 10k/15k divider to lower Arduino's TX swing.
But for RX, the Xbee runs straight into the Arduino. In theory this works, but I found 5V there and traced it back to the USB transceiver, which also drives the AVR's Rx line through a 1k series resistor. So you get 5V backfeed into the Xbee's TX output pin, which I am not okay with.

I found the same design problem also exists with the newer Arduino Xbee Wireless module and Arduino Wireless Protoshield, so any 3.3V RF module will experience this I reckon.

It looks like changing to the newer Leonardo might work, as the serial port OR'ing is not done in hardware. Is this correct? Is there a 3.3V Arduino?

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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