where to connect for extension ?

[Alessandro Sappia]

On Sun, Nov 23, 2008 at 1:40 PM, Al Johnson
<openmoko at mazikeen.demon.co.uk> wrote:
> On Sunday 23 November 2008, Alessandro Sappia wrote:
>> On Sat, Nov 22, 2008 at 11:46 AM, Al Johnson
>>
>> <openmoko at mazikeen.demon.co.uk> wrote:
>> > On Friday 21 November 2008, Alessandro Sappia wrote:
>> >> Hi
>> >> Me and some friends wants to connect the freerunner to some kind of
>> >> sensor. We saw that the debug connector give us the SPI bus.
>> >> is it a good choice ?
>> >
>> > It has been suggested in the past. I don't know if anyone's actually
>> > tried it yet though.
>>
>> which ones are the connection used in some other projects ? I wasn't
>> able to fount any
>> project involving some hardware extension.
>
> Several options have been talked about, but the only one I've seen documented
> was the DAB radio one soldered to the USB port.

We want the USB port free, even if going on USB will be easier for us.

>> >> is there a point where to take power near there (the debug connector
>> >> doesn't export it...
>> >
>> > R4701 and R4702 next to the debug connector have one end on the IO 3.3V
>> > line, but may not be a good place to pull power from. R7802 on the other
>> > side of the speaker has the 3.3V supply for the accelerometer which may
>> > be better. It probably depends on your power supply requirements though.
>> >
>> > I assume you've found the schematics:
>> > http://downloads.openmoko.org/schematics/GTA02/
>>
>> Yes, we have the schematics, but we really miss a good hardware hacker
>> between us :)
>> the 3.3V supply seems fine. le'ts give it a try. we have to give power
>> to an OPAMP.
>
> That doesn't narrow the requirements  down much ;-) What is it you're trying
> to do?
>
>> I didn't check if the soundcard is easily reachable, but we may
>> substitute the ADC on the
>> external sensor with it (opamps are always needed to get a bigger signal).
>
> Could be an option, again depending on what you're doing.

we're playing with life signals (aka heart rate)

An OPAMP connected to the 16F818 which talk SPI over the debug connector..

oh... do you know where to buy some unit of the flat cable sold with
the debug board ?


-- 
Alessandro Sappia
a.sappia at gmail.com