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 Forum index » DIY Hardware and Software » Microcontrollers and Programmable Logic
Microcontroller for Synths
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Kabzoer



Joined: Feb 07, 2011
Posts: 82
Location: Belgium

PostPosted: Mon Mar 12, 2012 1:31 pm    Post subject: Microcontroller for Synths Reply with quote  Mark this post and the followings unread

Hello everyone!

This is my first post here, I'm quite new to this stuff.
I'm really enjoying making little synth with my arduino UNO, but the
CPU speed and amount of memory is a bit limiting.
Is there an alternative that is maybe more synth-oriented
and not that hard to get started with? Because I really like the open-source
approach and the amount of examples that come with Arduino.

Thanks in advance!

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Dougster



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PostPosted: Tue Mar 13, 2012 7:01 am    Post subject: Reply with quote  Mark this post and the followings unread

You might consider the ARM Cortex M3, in particular the NXP LPC1769. There's a nice development board available from Embedded Artists:

http://www.embeddedartists.com/products/lpcxpresso/lpc1769_xpr.php

It's a little more involved than the Arduino, but it can do a lot of things.

FWIW, this board is what the latest MIDIbox projects are based on...

Regards,
Doug

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Blue Hell
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PostPosted: Tue Mar 13, 2012 9:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Or maybe http://www.raspberrypi.org/
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Kabzoer



Joined: Feb 07, 2011
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PostPosted: Tue Mar 13, 2012 9:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow, both very nice boards, the ARM Cortex M3 looks very professional,
but the Raspberry Pi looks easier...
I see raspberry Pi is especially designed for use with a pc,
you can plug a screen and keyboard in it, but I don't need that!
Can it drive an LCD display and some LED's?

Also, I maybe want to sell some units, so there should be an easy way to
get firmware updates (preferably without MIDI SysEx, like on the Shruti)

Thank you very much!

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Blue Hell
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PostPosted: Tue Mar 13, 2012 10:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Kabzoer wrote:
Wow, both very nice boards, the ARM Cortex M3 looks very professional,
but the Raspberry Pi looks easier...


I've got that same embedded artists thingie laying around here, and yeah that needs some work, although it comes with some example projects to get you started. And it will give you full controll over everything .. also meaning you need to write more code likely, and figure out how to connect up hardware.

The Raspberry thing runs an OS, which may indeed be easier for some things but also may get in the way when you want to do real time stuff. But I didnt try it (although I may get me one once the rush hour is over a bit).

But hey, they both don't cost much Smile

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Kabzoer



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PostPosted: Wed Mar 14, 2012 7:02 am    Post subject: Reply with quote  Mark this post and the followings unread

So the raspberry Pi has 256 MEGAbyte memory?
That's a lot compared to the ARM Cortex M3's 64kB...
But raspberry has no ROM so it neds an SD card? Am I right?

So, what are the cons fot the raspberry? Why doesn't everyone use it?

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emeb



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PostPosted: Wed Mar 14, 2012 8:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Kabzoer wrote:
So, what are the cons fot the raspberry? Why doesn't everyone use it?


Short list:

* you can't buy them yet.

* Documentation is limited.

* Processor can only boot from a crypto signed binary and they're not releasing the key.

* Not as much I/O or as flexible as other single-board computers in the same size / cost range.

It will be interesting to see how the community evolves around these though. There is a lot of potential, and many of the downsides listed above can/will change over time.
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Dougster



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PostPosted: Wed Mar 14, 2012 9:26 am    Post subject: Reply with quote  Mark this post and the followings unread

To be more specific, the first 10,000 sold out in 24 hours...

Also, there was a problem with the ethernet connector, so it's probably good to wait to see if there are any other issues...

Regards,
Doug

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Dougster



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PostPosted: Wed Mar 14, 2012 9:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Just to throw a couple more ideas out there...

Gumstix

Beagleboard

Pandaboard

Blackfin

Regards,
Doug

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Kabzoer



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PostPosted: Thu Mar 15, 2012 2:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Dougster wrote:

Gumstix

Beagleboard

Pandaboard

Blackfin


Those seem good, but they are a bit expensive aren't they?
I think the price should be less than €50, that way,
if you add extra components, casing, and design cost, one unit
would still be affordable (<€200)

I think I'm going for the ARM cortex! Very Happy

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Blue Hell
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PostPosted: Thu Mar 15, 2012 3:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

Kabzoer wrote:
I think I'm going for the ARM cortex! Very Happy


Keep us posted Smile

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Kabzoer



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PostPosted: Sun Mar 18, 2012 6:03 am    Post subject: Reply with quote  Mark this post and the followings unread

I looked a bit at examples for the LPC1769,
and they all seem waaaay over my head Embarassed

Maybe I'll stick a little longer to my arduino...
But when I compare arduino specs and LPC1769 specs,
the LPC looks a lot better. Shocked

And I found this:
http://hackaday.com/2011/02/01/what-development-board-to-use/
and forum post:
http://forums.hackaday.com/viewtopic.php?f=2&t=142

All pretty good alternatives, but how do I know if it's good for making synths?

Thanks a lot for all the answers I got already! Very Happy

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Dougster



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PostPosted: Wed Mar 21, 2012 9:26 am    Post subject: Reply with quote  Mark this post and the followings unread

Well, my number came up and I was able to place an order for the RaspberryPi. Estimated ship date? 8/8/12. Yep, you read that correctly, that's a five month lead time. Probably obsolete before it ships...

LOL!!!

Regards,
Doug

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JovianPyx



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PostPosted: Fri Apr 13, 2012 7:18 am    Post subject: Reply with quote  Mark this post and the followings unread

I just received a message on the music-dsp email forum indicating that the RaspberryPi has no real DAC, it uses one bit PWM instead.

My opinion: I wouldn't expect high fidelity sound from this.

$25 (or whatever it turns out to be) may seem like a great price, but I think that one does get what one pays for.

The thread title was "best board/set to do music on with minimal upstart?". The Pi was suggested along with other development board variants. All of which seem to have significant downsides, either obfuscated development setup, or pay-for-it compilers, or phone quality (or less) hardware. My personal opinion is that for decent audio quality, one really has to break free from the $25 constraint.

As Jan mentioned earlier in the thread, there also needs to be concern over the fact that there is an operating system standing between you and the hardware. While this may make coding connections to the hardware easier by using a library of functions, it doesn't address the need of DSP programmers for real-time execution.

In my view, if you already know you can code and enjoy it from using a low end board and you are looking for something better, then spend the money to get a decent piece of hardware and spend the time to learn its environment well. The benefit in that is you don't have to keep buying more boards when you realize "this ain't cuttin' it". As for being apprehensive about the unknowns - there are many folks on this forum and others that are more than willing to help you sort those out.

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Dougster



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PostPosted: Fri Apr 13, 2012 8:11 am    Post subject: Reply with quote  Mark this post and the followings unread

JovianPyx wrote:
$25 (or whatever it turns out to be) may seem like a great price, but I think that one does get what one pays for.

Indeed. The Raspberry Pi is really being sold as a small, cheap linux computer, not an audio development device. The $25 version is stripped down even further from the $35 version. It has only one USB port and no ethernet. It's a great way to get started with embedded linux though.

Quote:
The thread title was "best board/set to do music on with minimal upstart?". The Pi was suggested along with other development board variants. All of which seem to have significant downsides, either obfuscated development setup, or pay-for-it compilers, or phone quality (or less) hardware. My personal opinion is that for decent audio quality, one really has to break free from the $25 constraint.

I think that, in general, there is an inverse relationship between power and ease of use. To get the real power, you'll have to invest the time to learn.

At some point, I think you have to make a design decision. Microcontrollers are great for doing things like processing inputs (encoders, potentiometers, etc) and for displaying output (led, lcd, etc), but they aren't optimized for generating sounds. If you really want to generate and manipulate sound, some kind of DSP chip is going to be a better solution, whether it is implemented as a piece of hardware like the Freescale Symphony or as a core on an FPGA.

Maybe one of the hybrid chips would be a better solution - something with a combination of MCU and DSP functions...

Regards,
Doug (Hardest part is deciding what the real goals are...)

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JovianPyx



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PostPosted: Fri Apr 13, 2012 8:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Dougster wrote:
I think that, in general, there is an inverse relationship between power and ease of use. To get the real power, you'll have to invest the time to learn.


I love the statement: "there is an inverse relationship between power and ease of use." Too true.

Dougster wrote:
Maybe one of the hybrid chips would be a better solution - something with a combination of MCU and DSP functions...


hmm. Well, a dsPIC is just that, it's a full blown MCU and it has additional builtin DSP instructions that support at least a modicum of parallelism. The only serious complaint I have about it would be that the internal SRAM is a bit limited at 16Kbytes, but I expect this to change over time. In the meantime, I do have plans for a (more or less standalone) dsPIC project and I hope to use a dsPIC as a "front end" processor for gathering data from audio, pots, CVs and also to control an LCD and connect it to an FPGA which will do the hardcore DSP.

However, I think that the dsPIC by itself is at least a reasonable small scale DSP device, capable of a well featured monosynth or a small 4 voice synth.

Yes, there is some spool up time as there is with anything else. At least you can get them in DIP package and it is entirely possible to create your own board using stripboard (including being able to program it on that board).

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macumbista



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PostPosted: Sat May 12, 2012 4:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

I just had a little chat with Edgar from the CCRMA Satellite project. He's done extensive research, testing and benchmarking of embedded computers for audio purposes, and swears by the Beagleboards.

There's docs, code and some example projects here:

https://ccrma.stanford.edu/~eberdahl/satellite/

And this workshop listing from STEIM is an especially informative overview:

http://steim.org/event/ccrma-invention-embedded-instrument-design/

And finally a paper on the project presented at New Interfaces for Musical Expression (NIME):

http://www.nime2011.org/proceedings/papers/E03-Berdahl.pdf

Hope y'all enjoy these. And if you don't mind, I just posted a question about hybrid digital/analog synth modules here, in case anyone has some suggestions. Thx!

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alex_r



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PostPosted: Tue Jul 24, 2012 4:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi to all !

I started to develop a Soft Synth based on a STM32F4 discovery board.
It is a sample-based synth and due to the relatively simply tecnique used, the STM32F4 is capable to render up to 48 voice polyphony.
If it is of your interest, see a demo video of first release on http://www.youtube.com/watch?v=4JkhzH57Je4
So if you are oriented on a CortexM platform, I suggest you to look in the STM32F4 series.

I hope this can be usefull for you.
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cappy2112



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PostPosted: Sat Aug 04, 2012 12:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Kabzoer wrote:
So the raspberry Pi has 256 MEGAbyte memory?
That's a lot compared to the ARM Cortex M3's 64kB...


Yes, but you're comparing an SBC to a microcontroller. Not quite the same thing.

If you don't find something suitable for your project and can hold out until later this year, a 96Mhz Cortex M3 Arduino is supposed to be making its debut. Nothing about cost or features has been leaked yet, but I'd expect this to cost more than the Arduino 2560, and hopefully less than $100.

This will be the first Arm-based Arduino.

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PostPosted: Sat Oct 06, 2012 8:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Kabzoer wrote:
So the raspberry Pi has 256 MEGAbyte memory?
That's a lot compared to the ARM Cortex M3's 64kB...
But raspberry has no ROM so it neds an SD card? Am I right?

So, what are the cons fot the raspberry? Why doesn't everyone use it?


[quote]
ut raspberry has no ROM so it neds an SD card? Am I right?
/[quote]
Yes. currently it boots a custom version of Debian. You do need an SD
card.

The major con is that the I/O lines run at 3.3v, so you'll need a level translator if you're connecting to 5v.

One thing I don't like about these is the layout & packaging, but you have to keep in mind these are development boards.

There was a huge shortage for a while, but they seem to have caught up with the demand somewhat. I had to wait over 3 months- for the initial batch.
However, I recently won a second unit at a technical presentation.

The later runs of the board are already at Rev2, but the changes are very minimal.

The latest linux distribution lets you *easily* overclock the boards in 100Mhz increments. You can go up to 1Ghz, but that is way out of spec. No telling how long the board would last running that fast.

A nice little board, cheap and small.

If you see my post in the Max/MSP/PD forum, someone recently got PD running on the Rpi.

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cappy2112



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PostPosted: Sat Oct 06, 2012 8:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Kabzoer wrote:
So the raspberry Pi has 256 MEGAbyte memory?
That's a lot compared to the ARM Cortex M3's 64kB...
But raspberry has no ROM so it neds an SD card? Am I right?

So, what are the cons fot the raspberry? Why doesn't everyone use it?


No rom/bios. Yes. currently it boots a custom version of Debian. You do need an SD card.

One con is that the I/O lines run at 3.3v, so you'll need a level translator if you're connecting to 5v.

One thing I don't like about these is the layout & packaging, but you have to keep in mind these are development boards.

There was a huge shortage for a while, but they seem to have caught up with the demand somewhat. I had to wait over 3 months- for the initial batch.
However, I recently won a second unit at a technical presentation.

The later runs of the board are already at Rev2, but the changes are very minimal.

The latest linux distribution lets you *easily* overclock the boards in 100Mhz increments. You can go up to 1Ghz, but that is way out of spec. No telling how long the board would last running that fast.

A nice little board, cheap and small.

See my post in the Max/MSP/PD forum, someone recently got PD running on the Rpi.

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