Technical Ramblings

If you have a Macbook, and at some point, you get “Bluetooth not available” from your laptop, and “No information found” in your System Information app for Bluetooth, it might help if you try to reset the Macbook SMC, as described in Resetting MacBook and MacBook Pro System Management Controller (SMC). I had this problem for the past couple days, and doing this fixed it for me.

(This article is largely published so that others searching for “Bluetooth Not Available” may be able to find it before taking their Mac into the shop.)

Note to self:

The NMEA\_to\_DecDeg function is documented in Mapping Hacks, hack #62, “Build a Car Computer”.

(I’m going to be working quite a bit on my gsmlocation stuff in the next couple weeks, building up to a lightning talk presentation at Where 2.0 on June 13th. If you have a Bluetooth GPS and a Series 60 Symbian cell phone, please talk to me: I could use your help in building up a larger dataset.)

Today, there are a large number of cheap bluetooth GPS devices on the market. These devices allow you to connect to the device wirelessly, which is great for when you’re driving and don’t want cables draped all over the car.

However, what happens when you can’t drag your computer out to act as a display of your position? No bluetooth GPS on the market today for under $500 has a display of any kind. When you consider that these things can be had for $70, that makes purchasing one go from likely, to ridiculous. What’s the point of a handheld, easy to use GPS if you can’t use it to see where you are?

If you’ve been asking this question, I’ve got software which has an answer for you. GPSDisplay will allow you to connect to NMEA compatible Bluetooth GPS devices and display your position fix. It is written entirely in Python, using NMEA code from Forum Nokia. It requires only that you first install Python for Series 60 on your device, and should work on all first and second generation Series 60 phones. Simply download the .sis file, send it to your phone, and you’ll be all set to go — you can use your phone as a display for that new cheap Bluetooth GPS you bought, and stop dragging your laptop out into the woods to go Geocaching.

Geolocation is the technique of determining a user’s geographic latitude, longitude and, by inference, city, region and nation. There are a number of ways to do this: one of the common ones discussed on the internet (according to a Google search for “geolocation”, as we all know Google is the Answer) is geolocation via IP address. The kind I’m interested in is much more accurate: geolocation via GPS device.

I want to be able to know where I am. I want this for a lot of reasons, most of them geeky rather than actually reasonable. However, it would be nice to offer more specific statistics on where my pictures are actually taken with fine grain granularity that a GPS can offer. Additionally, some of my alternative projects – cell based geolocation and the like – could benefit from actual coordinates on which to base everything from restaurant locations to searches. Openguides is, in particular, one area that could benefit from this.

I want something that works over bluetooth. My laptop and phone both speak bluetooth, and something with an actual display is out of my price range, for the most part, so I want something I can use my phone to get data out of. (USB / serial obviously doesn’t work for that.) From what I understand, most GPS devices which support NMEA are going to work okay for communication, as there are tools out there which support them. (Whether I can get the thing to talk over bluetooth is a different concern, but one I’m becoming more proficient at every day.)

For a long time, all I could find for Bluetooth GPS devices were 200-250 USD and up. However, while discussing it with someone in #mobitopia on Freenode, I found the Delorme Bluelogger, a Bluetooth GPS device for $150. Matt already posted about our discussion, but I hadn’t yet.

I have some cash left over from Christmas, and I know that I almost never actually buy anything for myself. So, I’m going to splurge, and I’m going to get it. I’m going to learn to use it, and I’m going to do all kinds of neat things with it. Plans include:

• GPS Annotation of Photos – This rolls into my photo annotation project, and is part of the reason I was keen to get it done: I want to actual have some fun queries for normal people (rather than just RDQL-aware people) over my photos.
• Location Based Description of things for Openguides – Describing where things are with GPS coordinates allows searches by distance. Once I have that, the guide allows more niftyness.
• Association of Cell IDs to Geo locations – Tied to the previous, this allows me to know where I am based on a Cell ID: Useful for “what’s nearby”, as well as useful for the general “where are you” that I like to be able to do – with just my cell phone.

All in all, some of the apps I have in mind seem nifty, some geeky, some just demonstrative of something bigger. Some are RDF related, some are just fun. The Bluelogger seems like a decent tool to achieve everything I need to.

One of the nifties things I have on my cell phone is a bluetooth capability: the ability to communicate with other devices nearby at relatively high speeds over a wireless protocol. Bluetooth is a very useful tool for development: I don’t have to worry about USB cables or anything else, and I can talk equally well to my Linux desktop with an abicom BT adapter as I can to my Powerbook with its built-in bluetooth.

One thing that no one has mentioned yet about the new Python release is the Bluetooth console. It took some doing, but I finally got it connected to my Linux desktop, and found an app that will let me connect to the port. Now, I basically have a way to tell my phone what to do over Bluetooth:

[crschmidt@peanut ~]$ sudo cu -l /dev/rfcomm0 
Connected.
Python 2.2.2 (#0, Dec  2 2004, 18:12:32) 
[GCC 2.9-psion-98r2 (Symbian build 540)] on symbian_s60
Type 'copyright', 'credits' or 'license' for more information.
Type 'commands' to see the commands available in this simple line editor.
>>> 

This has sped up my application development significantly: with this in place, I can start to experiment with different code at a rapid rate: without sending almost identical files to the phone several dozen times to test them, nor typing on the 3650’s keypad to enter my code. I just type into a normal tty, and it acts exactly like a local python interpreter.

This is also possible, and documented as such, using TCP/IP over GPRS instead of Bluetooth. However, the speed restrictions of that cause it to be much less practical. It’s like typing into ssh over bluetooth: sure, it’s okay, but you almost never want to do it if you can avoid it.

Here’s what I ended up doing to get it working:
– Get a working bluez install. Bluez is the standard Linux protocol stack, and is built in to most recent kernels.
– Test that you can talk to the phone, using hcitool scan, hcitool info.
– Register an “SP” (serial port) service with sdpd. sdptool add --channel=3 SP
– Ensure that sdpd is running
– Set up an rfcomm port to receive the communications: rfcomm listen /dev/rfcomm0 3
– (On Phone) Open Python, then bt_console.py
– On the computer, you should see:

[crschmidt@peanut ~]$ sudo rfcomm listen /dev/rfcomm0  3
Waiting for connection on channel 3
Connection from 00:60:57:41:86:C2 to /dev/rfcomm0
Press CTRL-C for hangup

– Using taylor-uucp, type cu -l /dev/rfcomm0
– Welcome to the phone!

If you want to test to make sure it’s working, you can do something simple like:

import appuifw
appuifw.note(u'Howdy!', 'info')

from there, refer to the excellent Nokia documentation for more tips and tricks on what you can do. I think this is definitely a great example of what power the distribution has, and I’m surprised that more people haven’t been writing about it. Has anyone besides me (and Nokia employees) gotten this working?