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Author Topic: Arduino?
MichaelM

Posts: 17
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Post Arduino?
on: December 19, 2012, 16:41
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Has anyone played with Arduino microcontrollers for guitar/effects stuff?

We've been using them at work for hardware prototyping (computer input devices and stuff). However I've been given an LeoStick as a Christmas present, and I thought it would be cool to discuss how these things could be used in guitar effects.

This particular unit has 14 digital I/O pins (each pin is either input or output). These could be used for switching, controlling relays, LEDs, or reading the state of switches and buttons. It also has 6 analogue pins. The microcontroller doesn't have enough power to do do any real signal processing, but you could use the analogue pins to do things like read potentiometer values, or maybe use pulse width modulation to control things like the rate and shape of a tremolo effect using the microcontroller.

Anyway, I guess I'm just curious as to whether anyone else is using these things?

MichaelM

Posts: 17
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Post Re: Arduino?
on: December 19, 2012, 21:50
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Apparently I was wrong, Arduino boards can be used for some realtime signal processing. These guys have it working, though only with a 15Khz, 8bit sample rate.

https://interface.khm.de/index.php/lab/experiments/arduino-realtime-audio-processing/

Digital-
Larry

Posts: 192
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Post Re: Arduino?
on: December 20, 2012, 07:07
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I HAVE an Arduino, and I hooked it up and made it blink an LED (just to make sure it knew who was boss around here) but since then it's been sitting around awaiting its opportunity.

The most interesting projects I've seen include a little signal generator for audio testing, and doing an FFT (spectral analysis) in real time. I don't have that much interest in processing digital audio directly with it, but who knows... could happen...

https://www.instructables.com/id/Arduino-Waveform-Generator/

https://www.openmusiclabs.com/2012/08/arduino-fft-get-your-freq-on/

MichaelM

Posts: 17
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Post Re: Arduino?
on: December 20, 2012, 13:15
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Yeah I guess I was more thinking using the Arduino to control various aspects of an analogue signal chain. There's a lot you can do with the digital pins and some transistors. Even more if you use pulse-width modulation.

I've ordered some JFETs so I can mess around with switching the signal path in various ways. Will post results.

joe
Administrator
Posts: 224
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Post Re: Arduino?
on: December 21, 2012, 10:46
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Oh man — I am so interested. I have two Arduinos here that I've been MEANING to explore for, like two years. 🙁

I want more hours in each day, please!

Digital-
Larry

Posts: 192
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Post Re: Arduino?
on: December 21, 2012, 11:41
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The programmable tremolo.

Somebody's already done it! (but of course)

https://www.diystompboxes.com/smfforum/index.php?topic=95586.0

mwseniff

Posts: 149
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Post Re: Arduino?
on: December 21, 2012, 16:04
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I've been meaning to get an Arduino or Raspberry Pi to play with myself for a while. I've mostly played with Stamp processors which are less powerful but still cool. I designed a Stamp based circuit to control video projectors via their serial port for power, input switching etc. It is a very cheap solution for the university I worked at we also built and sold them to other users generating some income for our classroom technology dept. It has been very popular with people having permanent installs of video projectors. It worked on all projectors except Sonys which are great units but a pain to interface with almost any system available due to their serial port protocols. I also built a similar system to control switching for a couple of bars in town to control the audio system switching for PA, video and paging. You can idiot proof stuff easily with them. The newer generations like the Arduinos and Raspberry PI are much more capable but if I was doing any signal processing I would use some of the new generation DSPs that are very economical, easily programmed and easy to interface. I am helping a buddy that designs speakers to implement a DSP based audio processor for PA speakers. He designed and built some cool 5" drivers with massive magnets that sound great when used with a sub and some tweets. I have also seen some great Arduino based synth and midi controller circuits on the net lately. Sure beats the heck out of the 8 bit cpu systems I started fooling with.

Digital-
Larry

Posts: 192
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Post Re: Arduino?
on: December 21, 2012, 16:45
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I did get a Raspberry Pi a couple months back. As it is generally running Linux it is questionable whether it would be useful at the heart of an embedded system like an effects controller (because of Linux's occasional, unpredictable processing latency). I had more dastardly things up my sleeve and tried to get the Linux JACK audio subsystem working, so I could run things like SooperLooper. But ultimately, the audio drivers on this thing don't like to play well with JACK and I don't think it's a high priority for anyone to solve that.

The Raspberry Pi, when running a Linux graphical desktop is just CRAWLING - open up the web browser and watch the CPU redline for two minutes. So up to now I have just written some programs in Python for keeping track of how much time my kids spend playing video games and a kind of cool screen saver. Next up is setting my brother up to use one to sense temperature and humidity for his orchid growing operation. And I'd like to use it also for doing time lapse on the cheap with a webcam, to get the kids interested in the inventing part of technology.

I also just got a CubieBoard which is targeting an Android experience out of the box. I've just started writing some Java apps for Android and so who knows how far I will get? More interested in musical applications recently. The BeagleBoard has a TI DSP built onto it but that's like a $179 experimenter board compared to about $35 for RPi and $50 for CubieBoard.

mwseniff

Posts: 149
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Post Re: Arduino?
on: December 22, 2012, 20:07
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Those are the sort of things I was thinking of doing with a Raspberry Pi. It's a drag that the JACK subsystem is not stable. Is it possible to dump the graphical interface and just run command line stuff to speed it up? Heck I always thought a graphical desktop was a bit heretical on any form of unix but I am an old guy after all. Tho' I will say I liked running Sun Solaris for the chemistry instruments as it let me spend a lot less time holding the hands of PHDs when they were using the instruments they spent a fortune on. I need to look at the Cubie board especially if the real time capabilities of Android have gotten to a useful level.

Digital-
Larry

Posts: 192
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Post Re: Arduino?
on: December 22, 2012, 22:45
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Yes, I am running my programs just from the console. I used Python and the Pygame library for graphics, timing and sound routines. I have the same thing installed on my PC so I develop on the PC and then bounce the code to the Pi through a Subversion repository. Even without running the OS GUI, Python timing is not accurate - maybe 5% slow. Under the GUI it's more like 20% slow.

I think less of the Pi in terms of the real I/O powerhouse and more something you want to use BECAUSE you want to use Linux in what amounts to a pretty stripped down environment. For example, any sort of sensor monitoring that presents the results on a web page is a good Pi project. I have it connected to my wireless LAN and I can get a console over SSH and do all sorts of development that way really conveniently.

I'm getting a new "B" version Pi with 512 MB RAM (double what I have now).

Regarding Android, supposedly, in 4.2 Jelly Bean improved audio performance and even support for USB devices was added? But nobody's treating Android as a media platform so it may be a long time coming. One guy supposedly came up with his own workaround...

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