issue with RFID module

boardnewbie

I just got RFID module and i connect VCC to USB as power source , SOUT to serial pin 2 , GND and /ENABLE to ground of USB port.. and i try to use it in hyper terminal try both com1 and 2 but not seem to work...
anyone out there could help PLZ..

Thank a lot
newbie

Jon Williams

It's not likely your USB port is assigned to COM1 or COM2, and even it it was, the data coming out of the RFID is probably not the correct polarity -- you may have to invert it.

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Jon Williams
Applications Engineer, Parallax

Bruce Bates

Jon -

Above and beyond that, if I understand correctly what "boardnewbie" is trying to do, the USB port doesn't have sufficient, or barely sufficient power to drive the RFID unit, does it?

Regards,

Bruce Bates

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Jon Williams

I don't know -- I've heard USB ports can supply 500 mA; is that wrong? I wouldn't attempt to drive it from the USB supply, but that's just me.

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Jon Williams
Applications Engineer, Parallax

Chris Savage

Initial power-up current of the USB Port is limited to 100mA.· Once the USB controller is enumerated the current limit is raised to 500mA.· As far as I know the device must request to be recognized as a high-power device for this to happen.· Usually the device will control switching of the power if it is a high-power device so that when the device has been recognized as high-power it switches on the connected equipment via a MOSFET.· If I am reading the FTDI sheet correctly by default they do not support anything over 100mA on the bus.· You must write a register in the EEPROM of the chip (FT232R) to sepcify up to 500mA of current draw.

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Chris Savage
Parallax Tech Support
csavage@parallax.com