Nokia 770 + a random Bluetooth GPS + Maemo Mapper + Google Maps = fun.

Nokia 770 and BT-308 GPS receiver
Nokia 770 and NaviLock BT-308 GPS

The fun part consisted of

  • Patching Maemo Mapper so that it can use Google satellite map pictures.
  • Banging my head against the wall trying to understand why Maemo Mapper won't talk to the GPS today, when it worked perfectly yesterday.
  • Googling for BT-308 protocol descriptions.
  • Discovering that BT-308 speaks two protocols: NMEA-0138 text protocol and SiRF binary protocol.
  • Discovering that Maemo Mapper only speaks (well, listens to) NMEA-0138.
  • Discovering that gpsdrive/gpsd that I tried yesterday evening (without much success) tell the GPS device to switch to the binary protocol (which is apparently the same that Garmin devices use).
  • Discovering that turning the GPS off and back on does not switch the protocol back to NMEA.
  • Reading the SiRF binary protocol refeference manual and writing a short Python script to connect to the GPS via Bluetooth and tell it to use NMEA.

Screenshot of Maemo Mapper
Maemo Mapper