USB-powering an M6E Reader Module

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daneloctober

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I'm not sure if this is the right place to post this.. but anyway...

I was tasked to power a ThingMagic M6E reader module through USB ports from a laptop. The reader is configured to draw a maximum of about 800mA at 5V, so I figured all I had to do was connect it to 2 USB ports: 1 port for communication (FTDI to USB), the other for additional power. But then I discovered that you had to ASK the host to enable the USB port to give more current, otherwise, you only get about 100mA max from a USB port.

The USB for communication (the one with the FTDI interface) I think is all set to get 500mA, but the other USB port, I've read that all I had to do was use a 200 Ohm resistor to practically short the D- and D+ pins so I can get more than 100mA (without having to "ask").

The question I have is, will the reader draw equally from both ports if I short the data pins on the port dedicated to provide additional power?... Remember, I will be drawing a maximum of 800mA. I'm not really sure what would happen if I draw more than 500mA from either port... I guess the USB ports will shutdown or something...

Here is a schematic of what I'm trying to describe:


Thank you very much!
 

If you have USB 3.0 then you can go with several amperes, lots PC motherboards support over 500mA on USB 2.0 ports (800-900mA).

You can use USB Power Injector to supply power from external source to device. With this you will avoid damaging of usb connector pins on long time usage.

:wink:
 

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