External GPS Receiver

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There is an ongoing work around a GPS Free Stack implementation.

Contents

[edit] GPS

A nanote GPS powered is interesting step for developing new features for this pocket computer.

This page provides information about a cheap/lazy first approach of hooking up a closed-source GPS module to the Nanonote.

[edit] Software

[edit] Graphical

TangoGPS is an application that allow show maps at location that the GPS gives, it requires internet connection at first but maps can also be cached and transfer for offline browsing.

I loaded just for see if runs, and runs, take about 30 seconds to load and seems some small but not too much due screen size, it was in the openwrt firmware which uses frame-buffer.

I tested TangoGPS in JLime firmware witch runs a X Sever and load speed improves to the half compared to openwrt, and also key bindings like i (zoom in), o (zoom out) and arrows keys are working.

Nanomap seems support gpsd latelly, that worth a try as is included in default openwrt compilation

[edit] Background Daemon

Gpsd is the daemon that could run in background. A good idea is add it boot time to improve responde in getting fix position.

Gpsd try to guess the communication to the nanonote, it can be hacked in a good way (by configure script) and allow fix values like speed and support for the protocol that the device just need (seems not needed at all as is fast enought).

For a testing environment i recommend run gpsd from ssh/tty like this:

 gpsd -nNG -D 10 /dev/ttyS0

Note the -G will allow you to run software like xgpsd in the computer side to debug things as well.

And the -D allow debug if the gpsd is really understanding/receiving gps information.

All this is already ported in openwrt and Jlime :)

[edit] Textbased

There are other console clients very usefull like an starting point.

 cgps   <===   basic position not fancy maps
 gpxlogger  <=== logger for traces, very usefull for helping osm and other tracking applications.

cgps is not in openwrt

[edit] Debugging

 cat /dev/ttyS0   <===  just look ;)
 stty <=== to fix port speed and more stuff


[edit] Hardware

[edit] Closed source

  • So i have for testing a SIM548 Module (GPS/GSM) in a custom board
  • For Ya there are ideas for a u-blox 5 AMY GPS module
  • RXM-GPS-SR (from tuxbrain)

[edit] Free Stack

  • some front-end GPS RF ICs have open datasheets, for example SE4120L
  • there are also free stack in software and hardware implementations that allow correlate GPS/GNSS raw data and provide a fix point.

[edit] Requirements

  • Serial port working on stable uboot branch (TP4/TP5)
  • You need wire TP4/TP5 terminals fro the nano [1]
  • Confirm that power module can drive GPS with no side effects

[edit] Issues

  • Issue related with the SIM548 module confirmed in both openwrt and Jlime firmware, also in two Ben boards
 GPS works just when the TX pin from it is wired to the Nanonote RX
 But if RX is wired the transmission stoped :/, seems not be a power issue after tested with separate 3V3 power
 Is not gpsd, it also happen with picocom terminal and cat ;).All using a SiRF protocol.
I swiched to a second uart port in the gps module, it uses NMEA protocol and then work now.

Possible solutions comments http://en.qi-hardware.com/pipermail/developer/2010-July/003298.html

  • Cant open /dev/ttyS0 using openwrt firmware

Edit:

/etc/inittab

And comment the line about ttyS0 that will solve the problem after next reboot

#ttyS0::askfirst:/bin/ash --login

[edit] Pictures

[edit] Static Tests


[edit] Moving Tests and Out Door

[edit] Video

http://vimeo.com/13144803 {{vimeo>13144803?medium}}

Pending upload in ogg

[edit] To do

  • Arrange all this wires/boards in a better way and try outside (done)
  • Compile or install nanonomap and check how it works (WIP)
  • Get gpsd utils in openwrt (just gpsd now)
  • Get a tiny/portable GPS with tiny Antena SMA comptible (Ideas?)

[edit] References

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