Getting NMEA data from an Inforad GPS speed camera detector
19 Nov 2009Some time ago I came across a post in the EeeUser forum alerting me to a cheap (£7.50) unit which was aimed at alerting drivers to speed cameras, however it also happens to provide a stream of standard NMEA data on a serial line. If you wish to obtain these units now they are readily available from ebay for under £10 .
Having followed the instructions that came with the unit (including no mention of direct GPS functionality) and installed the provided software in windows xp I got nowhere, so I tried it on linux. The device is actually a serial device and the cable which is included is in fact not a conventional USB, cable despite having a USB-A and USB-B plug at either end, it is an FTDI usb-serial adaptor which has linux kernel support. I then found it was possible to connect to it at 4800 baud using putty or cutecom or whatever your favorite terminal happens to be and standard NMEA data is displayed.
On closer examination of the cable the USB-A end can be split apart to reveal a simple Serial to TTL converter based in the PL2302 chip, this allowed me to find drivers (available here http://www.prolific.com.tw/eng/downloads.asp?ID=24) for all versions of windows and receive GPS data over serial in the same method as with Linux.
This means that the cable could easily be used for any 5V TTL applications required and also that the GPS unit would be ideal for interfacing with an arduino or similar system as the points for connection can be easily seen on the circuit board: