[PD] [SPAM] Re: gpio on the raspberry pi from within pd ?

[Dan Nigrin]

On 7/24/13 7:16 AM, "Charles Goyard" <cg at fsck.fr> wrote:


>J Oliver wrote:
>> > So from your post, it seems quite straightforward to be able to
>> > access the GPIO pins from within Pd.  But I need to be able to
>> > create variable voltages (between 0 and 5v) on those pins.  In the
>> > post above, you mentioned that you send a float to the gpio object
>> > to write a value to the pin - would sending a 0.5 for example give
>> > me 2.5v on the pin?  Or is it only on/off (0 or 5v)?   If the
>> > former, I'm all set!  If the latter, I'll need to figure out how to
>> > simulate a reduced voltage at the pin (likely using PWM or something
>> > ­ but I'm not really sure how I would do thatŠ)
>
>You can add a resistor and capacitor to build a RC filter, and you'll
>get a voltage out of pwm. You will have to experiment with different
>values to get something stable and fast enough.
>
>See these pages for some information about that:
>http://jeelabs.org/2013/06/30/from-pwm-to-voltage/
>http://dev.emcelettronica.com/how-to-use-pwm-to-generate-analog-or-analogu
>e-voltage-digital-circuits-part-2
>http://sim.okawa-denshi.jp/en/PWMtool.php
>
>As of 3.3V to 5V you can use a transistor before the RC filter.

Thank you, those links are very helpful!!

Dan
-- 
Dan Nigrin / Defective Records / http://defectiverecords.com
CycliC, M185 & Klee Sequencers / MC-4 & MC-202 Hack / Audio Plugin Player
/ General MIDI Player / Major Malfunction
Jack OS X / http://jackosx.com