daneloctober
Member level 2
- Joined
- Jan 28, 2011
- Messages
- 52
- Helped
- 2
- Reputation
- 4
- Reaction score
- 2
- Trophy points
- 1,288
- Activity points
- 1,708
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!
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!
