interactive media Archives - Page 5 of 28

January 19, 2013June 25, 2014

Raspberry Pi with Pd: audio test

notes

In an audio pass-through test using Pd, with a USB sound card (Griffin iMic), the maximum stereo sample rate before ‘breakup’ is 32000.In mono, it sounds “ok” at 44100. Latency seems low enough to use for music but I’m too sleepy to figure out the numbers.

I don’t know enough about Linux audio to say if the performance deficit is due to ALSA drivers, the sound card, background processes, pd, the CPU, or what?Anyway I ‘m guessing R-Pi will spawn interesting synths and lo-fi FX processors. They’re cheap enough you could use them in parallel.

Prediction: They’ll double the speed, and sell a million more by the end of the year. We’ll see a range of ‘Pi’ clones which run the same Linux distributions, but offer various speeds and IO options. It feels like the democratization of manufacturing has taken another huge leap.

January 18, 2013June 18, 2014

pd-extended on Raspberry Pi

notes

Using installation instructions from Pd site:

http://puredata.info/downloads/pd-extended-0-43-3-on-raspberry-pi-raspbian-wheezy-armhf

Installation worked fine. I tried running the GUI under xterm and it was a disaster. Then, using this post, I was able to get a test patch (sine wave with LFO) running in terminal mode:

http://log.liminastudio.com/programming/running-puredata-on-the-raspberry-pi

Note: I changed the actual command to this due to the fact I’m running pd-extended and a USB sound card:

pd-extended -nogui -noadc testPatch.pd

This post from same source has instructions for installing pd-extended (disaster) but a very nice version of the test patch called testPatchExtended.pd

http://log.liminastudio.com/writing/tutorials/how-to-build-pd-extended-on-the-raspberry-pi

(another update) running Midi:

To run midi you need to specify the device on the command line. First I plugged in the m-audio key station 49 and rebooted RPi

To get a list of devices use:

pd-extended -nogui -listdev

Then to run a patch with midi

pd-extended -nogui -noadc -midiindev 1 testMidi.pd

Here is a page with more information on command line options

http://crca.ucsd.edu/~msp/Pd_documentation/x3.htm#s4

(another update) Testing with Griffin iMic. Bad news when doing an ADC->DAC passthrough, sample rates above 32000 don’t work in stereo. However 44100 and 48000 sound fine in mono.

At the higher rates in stereo, the audio breaks up. Oh well. Need to try the Behringer audio box, but I’m assuming there will be no difference. Only possibility would be to somehow devote more system resources to audio.

January 18, 2013February 3, 2013

raspberry pi – external sound card sucess

Installed a Griffin iMic USB sound card on Raspberry Pi today.

Here’s how:

plug in imic
Edit alsa config file so that imic is default sound cart
test

Details

For editing alsa, follow instructions at beginning of this post for editing /etc/modprobe.d/alsa-base.conf

But you can stop following the instructions after the first reboot.

http://www.jackenhack.com/raspberry-pi-usb-audio-quality-problems/

For testing, use this command:

sudo aplay /usr/share/sounds/alsa/Front_Center.wav

January 18, 2013June 16, 2014

Xbee guide

A comparison of various xbee radios. You can get up to 15 miles, probably more with line of sight, but the disadvantage is that you can’t rely on outside help, like ham radio operators to help decode the telemetry signal.

From Sparkfun

https://www.sparkfun.com/pages/xbee_guide

January 18, 2013June 24, 2014

Arduino INPUT_PULLUP mode

notes

When reading the value of a switch with Arduino, its useful to set the INPUT_PULLUP mode so you don’t need to use an external pullup resistor. By the way, the internal pull-up resistor is 20K ohms.

See this tutorial:

http://arduino.cc/en/Tutorial/InputPullupSerial

If its not clear what a pull-up resistor does, read the links on this forum post.

http://arduino.cc/forum/index.php/topic,22274.0.html

Everybody has their own way to explain it. I would say that when the switch is open, the pull-up resistor weakly pulls the logic value high, so you don’t get random signal readings.

January 15, 2013June 18, 2014