Jonathan Oxer
[Blog]
>> USB RFID Reader
Sat, Apr 15th 8:50pm 2006 >> Tech Toys
My first prototype 134.2KHz RFID reader used a MAX232 level converter to connect to a host computer by RS232, but my laptop doesn't even have old-style serial ports so thanks to a micro-USB USB-to-UART bridge supplied by Dontronics (thanks Don!) I put together a reader with a USB interface.
I hadn't used the micro-USB modules before but I'm totally impressed. The module is incredibly small: it's basically just a B-type USB socket with a microcontroller mounted directly on the bottom and some header pins. They're totally plug-and-play: the device enumerates itself as a standard serial port on the host computer so you can talk to it with bog-standard tools like GTKTerm just like any other serial port, and at the other end it presents TTL-level serial I/O lines. It even provides pass-through ground and +5V connections from the host computer so you can power a device straight from it if you don't need much power.
So in the end all I had to do was rip the MAX232 off the reader, pop the micro-USB device in its place, remove the 5V voltage regulator and use the regulated output from the micro-USB instead, and plug it in. Linux recognised the device, GTKTerm connected straight through to the microcontroller in the reader, and it Just Worked.
Rock!
My first prototype 134.2KHz RFID reader used a MAX232 level converter to connect to a host computer by RS232, but my laptop doesn't even have old-style serial ports so thanks to a micro-USB USB-to-UART bridge supplied by Dontronics (thanks Don!) I put together a reader with a USB interface.
I hadn't used the micro-USB modules before but I'm totally impressed. The module is incredibly small: it's basically just a B-type USB socket with a microcontroller mounted directly on the bottom and some header pins. They're totally plug-and-play: the device enumerates itself as a standard serial port on the host computer so you can talk to it with bog-standard tools like GTKTerm just like any other serial port, and at the other end it presents TTL-level serial I/O lines. It even provides pass-through ground and +5V connections from the host computer so you can power a device straight from it if you don't need much power.
So in the end all I had to do was rip the MAX232 off the reader, pop the micro-USB device in its place, remove the 5V voltage regulator and use the regulated output from the micro-USB instead, and plug it in. Linux recognised the device, GTKTerm connected straight through to the microcontroller in the reader, and it Just Worked.
Rock!
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