Recently, Forum Nokia released a new developer tool for measuring S60 application's power consumption (Nokia Energy Profiler) Here are some results and conclusions about power usage while using ExtGPS on Nokia E90 communicator.

The biggest power hog is the screen backlight. Alone, it consumes about 650 milliwatts of power. When the screen is dimmed and screen saver is activated, the power usage is about 70mW - this is when the only running application is energy profiler itself - I guess the profiler itself uses some power as the official standby times suggest around 20mW power usage in idle.

When GPS has obtained a fix and laptop is connected via Bluetooth port, the long time power usage is about 530 mW (dimmed screen). E90 has BP-4L battery which is rated for 3.7V 1500mAh. This totals about 5.5 watthours, meaning that the battery should be good for 10 hours of GPSing!

N95 has 950mAh battery, which could last for 6 hours 30 minutes, if you don't use any other phone features. This about the same usetime as those "normal" external BTGPS units.

To make our series complete, here are the instructions how to setup ExtGPS for Linux applications, using Bluetooth serial port.

Unlike the other howtos, this one is command line based. Probably suits better for Linux enthusiasts :-)

Make sure ExtGPS is up and running and your phone is discoverable. In the following dumps, aa:bb:cc:dd:ee:ff should be your phone's Bluetooth MAC address.

Perform a scan for "Serial Port" services:

ubuntu@ubuntu:~$ sdptool search SP
Inquiring ...

Searching for SP on aa:bb:cc:dd:ee:ff ...
Service Name: Symarctic ExtGPS
Service Description: Share phone's built-in GPS ...
Service Provider: Symarctic Solutions
Service RecHandle: 0x10016
Service Class ID List:
  "Serial Port" (0x1101)
Protocol Descriptor List:
  "L2CAP" (0x0100)
  "RFCOMM" (0x0003)
    Channel: 5
Language Base Attr List:
  code_ISO639: 0x656e
  encoding:    0x6a
  base_offset: 0x100

(... continues with other services...)

Create /dev/rfcommX device for ExtGPS, by "rfcomm bind" command. Note the parameters, "1" is the id for /dev/ entry, mac address and the last one is RFCOMM channel ID from service, in my case it's channel 5 (chanel no. 5 ?):

ubuntu@ubuntu:~$ sudo rfcomm bind 1 aa:bb:cc:dd:ee:ff 5

When application connects to /dev/rfcomm1, it's opened to ExtGPS. You can test the connection, e.g.:

ubuntu@ubuntu:~$ cat /dev/rfcomm1

After this, the connection icon on ExtGPS should be green and device name shown next to it. If the satellite icon is also green (meaning a fix), you should now see raw GPS NMEA data on your terminal. Issuing Ctrl-C should break the connection, turning the connection icon back to red.

New firmware version, 07.40.1.2, enables A-GPS also on E90 using ExtGPS v0.31. You can update software yourself using Nokia Software Updater (www.nokia.com/softwareupdate).

Just a word of caution, when I updated the phone, the Updater reported "Connection to Phone Lost". At this stage, the phone had black screen. After removing battery and powering up the phone booted normally.

AGPS Satellite fixes are now obtained about 50 times faster...

This version changes criteria for used locationing method, allowing location method to cost (for sending data). In effect, this enables A-GPS (network assisted GPS) positioning on N95's latest firmware upgrade.

Download ExtGPS

Beta version of ExtGPS is now publicly available. I'm collecting more features for upcoming versions, feel free to post your suggestions here.

Currently under planning/evaluation:

- Satellite information
- Dummy NMEA data while obtaining satellite fix
- USB connectivity

Not very likely to be implemented: (please comment on these)

- GPSd support (via WLAN)
- Native S60 version (not very likely unless there's some very important feature we miss with MIDP, as applications using Location capability need to be Symbian Signed, which is major headache)