Turn FR into bike meter

Risto H. Kurppa risto at kurppa.fi
Thu Jul 2 17:34:00 CEST 2009


I bike and I have a Freerunner.

GPS apps, like omgps are able to show & record the position, speed,
length of track etc.

1) I'm missing the cadence display = the number of revolutions of the
crank per minute; roughly speaking, this is the speed at which a
cyclist is pedalling/turning the pedals.

-> any ideas how to build this, both hardware and software (=how to
convince some GPS software guy to implement it :)

I was thinking of using the audio jack or to be more specific, the
microphone line. Each revolution would connect the wires (with a
resistor maybe?) to create a pulse in the microphone line. This could
be recorded and analyzed with SW.

2) Another thing missing is a tool to analyze my GPS track on-the-fly:
show the speed vs. time plot.

Thanks for your ideas! Extra thanks if I'm able to have this up and
running in a week, planning to do a 170-200km bike trip in a day :)

(more over, I think there could be a need for proper bike-oriented app
for Freerunner. Map display's nice but many other features might come
more important for people riding bike, like heart frequency, cadence,
current speed, avg, maybe also set target length and estimate the time
to reach it (I know Navit ~does this) etc.. -  anyone interested?!)


ps. http://www.obico.de/

| risto h. kurppa
| risto at kurppa dot fi
| http://risto.kurppa.fi

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