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USGlobalsat ND-100S GPS receiver works with USB Host library

ND-100S GPS receiver connected to USB Host shield

ND-100S GPS receiver connected to USB Host shield

After posting an article about interfacing USB GPS receiver to Arduino I started receiving e-mails from people asking about a decent inexpensive GPS receiver compatible with USB Host library. After some research and testing I finally found a device which I really like.

ND-100S from USGlobalsat is small, inexpensive (less than $30 shipped at DealExtreme) GPS receiver with excellent characteristics. Below are some bullet points:

  • Lightweight – my scale shows 19g for the dongle without connector cover. It is possible to get weight close to 15g by removing the case, USB connector and hardwiring the module to USB Host shield.
  • Sensitive – SiRF Star III high sensitivity GPS chip allows this module to lock in less than a minute from my basement (!). Outdoor performance is simply amazing while power consumption stays around 50ma.
  • Easy to use – the module uses Prolific PL2303 USB to serial converter supported by USB Host library 2.0 and the sketch from the previous article works without any modifications. Also, the module has status LED showing when GPS position is fixed – comes in handy during field tests when serial console is not available. The dongle ships with semi-rigid USB cable which can be used as a raiser.

Overall, ND-100S is very small, sensitive and inexpensive GPS receiver. It can be used with USB Host shield using PL2303 USB to serial converter support in USB Host library rev.2.0. I have a couple of projects in mind which would use this receiver – will post as soon as I have more information about it.

Oleg.

Communicating to GPS Receiver using USB Host Shield

Navibee GM720 connected to Arduino

Navibee GM720 connected to Arduino


Here is another quick demonstration of USB Host Shield 2.0 Library. This article describes how to communicate to Navibee GM720 GPS receiver based on SiRF Star III chipset and PL2303 USB to serial converter. This GPS device is available on eBay for around $25 new, used units can sometimes be found for $10 or even less. The receiver has waterproof case, magnet mount and comes with 6 foot cable. Another nice feature of this device is its 40mA current consumption. Here are some pictures of the unit – PCB, internal antenna, as well as front and back of the original packaging.

“Classic” GPS receiver sends and receives NMEA 0183 messages via serial port at 4800 bps. Modern GPS units often support faster speeds and vendor-specific messages. However, they mimic classic GPS unit behavior – at power-on they start sending basic navigation messages at 4800 bps. The following sketch outputs messages, received from Navibee GM720 GPS unit via its built-in PL2303 USB to serial converter connected to USB Host Shield. Full text of the sketch is available on gitHub, below is just a fragment where speed is set to 4800.

The OnInit() member function is called to change serial parameters after initialization. A lc structure of type LINE_CODING is declared on line 14. It is filled with baud rate (line 15) and number of data bits per byte (line 18) and then sent to Pl instance in line 20.

Compile the sketch, load and run. The output is depicted on a screenshot after the code fragment.

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