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Can Bi-directional Logic Level Shifter drive an XBee? (quest
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Can Bi-directional Logic Level Shifter drive an XBee? (quest

by christinayang11 on Mon Jul 16, 2018 9:50 am

Hi,

I'm very new to electronics so I apologize for my lack of knowledge.

I wanted to use an XBee Series 1 module with an Arduino Mega that would also have the TFT Capacative touch screen shield connected to it. Since the RX/TX pins are 5V, I was going to use a logic level shifter to convert them to the 3.3 V needed for the XBee module (https://www.adafruit.com/product/1875); however, I saw on the description page that the output drive is low, so I'm not sure if it would have enough power for the XBee module.

In the logic level shifter data sheet, it says that the continuous output current is 50 mA, and the Xbee data sheet says that the TX peak current is 45 mA, the RX peak current is 50 mA, and the transmit current is 45 mA. Does this mean that the logic level shifter will be able to work with the XBee? I saw that there is a uni-directional level shifter with higher output drive, but I would be more comfortable using the bi-directional one because it's labelled (I'm not good at reading data sheets, so it would be harder to use the uni-directional one).

Also, I saw in the logic level shifter data sheet that a pull-up resistor should be used with OE for high-impedence. Is this required or will it still function without it?

Thanks so much for your time and help!!

christinayang11
 
Posts: 3
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Re: Can Bi-directional Logic Level Shifter drive an XBee? (q

by adafruit_support_bill on Mon Jul 16, 2018 10:03 am

In the logic level shifter data sheet, it says that the continuous output current is 50 mA, and the Xbee data sheet says that the TX peak current is 45 mA, the RX peak current is 50 mA, and the transmit current is 45 mA. Does this mean that the logic level shifter will be able to work with the XBee?

The peak currents mentioned in the XBee data sheet are for the 3.3v supply to the VCC pin. This should be connected directly to the 3.3v pin on your Mega.

The level shifter is only intended for shifting voltage level for logic signals (e.g. Rx and Tx). These use negligible current so the chip will easily handle it.

adafruit_support_bill
 
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Re: Can Bi-directional Logic Level Shifter drive an XBee? (q

by christinayang11 on Mon Jul 16, 2018 10:13 am

Okay, thanks for your quick and helpful response! I'll go use the bi-directional level shifter then!

Also, I have another question. The 3.3 V pin on the Mega will be covered up by the touchscreen shield, so I could use an external 3.3 V source for the Xbee?

christinayang11
 
Posts: 3
Joined: Mon Jul 16, 2018 9:30 am

Re: Can Bi-directional Logic Level Shifter drive an XBee? (q

by adafruit_support_bill on Mon Jul 16, 2018 10:19 am

Yes, you can use an external source. But be sure to connect the ground from your external supply to the ground of the Mega also.

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Re: Can Bi-directional Logic Level Shifter drive an XBee? (q

by christinayang11 on Mon Jul 16, 2018 10:54 am

Great! Thanks again for all of your help!

christinayang11
 
Posts: 3
Joined: Mon Jul 16, 2018 9:30 am

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