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Getting a GPS keyfob to talk to a PIC over USB

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Getting a GPS keyfob to talk to a PIC over USB

By KeithB
-  Tue Sep 13, 2011 10:06 am #133278
I have a QStarz GPS keyfob that sends out NMEA strings over USB (and bluetooth - but that is too expensive). Can I get one of these:
http://www.sparkfun.com/products/718

(an FT232RL breakout) and connect the two together and start receiving strings? Or is there some USB magic (Enumerating?) I need to do in order to make my FT232RL a bus "master"?

Re: Getting a GPS keyfob to talk to a PIC over USB

By tetsujin
-  Tue Sep 13, 2011 1:00 pm #133287
USB is a host-driven bus. For two devices to communicate, one must act as the host, and the other as a slave device.

Most devices operate as slave-devices only. This includes the FTDI chip and (I expect) the GPS as well. The typical expectation is that a PC will act as the USB host.

That said, there are microcontrollers with USB host capabilities (anything with "USB On The Go" or "USB OTG" basically means it can act as a USB host) and chipsets you can connect to add USB host capabilities to a microcontroller. (See the "Arduino USB Host Shield" for instance.) There is a certain amount of code out there that can help you if you want to make your microcontroller act as a USB host - there are libraries available for making USB devices and hosts with various devices - but I think you'll still face a bit of an uphill battle, as almost anything USB-related is a bit of a challenge IMO.
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