Why is there no RX (DIN) logic level shifter on Xbee Arduino Shield USB-C?

Wireless & IoT Digi XBee
1

Seems like a major oversight since this can damage the xbee and the hookup guide explicitly states the shield can be powered from an R4 board.

Neglecting the fact I could fry my xbee, here is what I tried.

I can get the XBee working if I power the shield with USB since Arduino’s Schottky diode drops V5 voltage down to 4.67V. However, if I power Arduino from Vin (resulting in V5=4.92V) or directly from V5 using sparkfun 5V buck regulator (V5=5.07) the xbee does not work.

3

I spent a while poking through the docs

and I believe you are correct :-/

It looks like 5v power is disconnected by default (linked above) but there isn’t any level translation on the IO pins - feel free to create an issue on the shield’s github to alert the engineering team

4

Thanks Russell.

I believe I confirmed the issue by connecting Vin to7V.

pin:Volts

Arbuino Vin: 7.02V

Arbuino 5V: 4.92V

Arduino 3.3V: 3.29V

Xbee 3V3: 3.36V

Xbee RXI: 4.22V

In this case the Xbee does not work. But if I pass RXI through SparkFun’s bi-directional logic level converter then RXI becomes 3.24V and the Xbee works. I’ll create an issue on github.

Martin

5

Good job - sounds like a plan :slight_smile: