[sdiy] The Owl: ARM fx pedal

Terry Shultz thx1138 at earthlink.net
Thu Apr 25 05:43:34 CEST 2013


Hi Martin,

Let's review some facts to consider for Open Source based projects.

Tools: 
	Free or near Free tools depending on Memory size limits i.e. IAR, Keil, CodeWarrior and Code Sourcery. Obviously CodeWarrior is Freescale product Centric.
Perhaps others can list other Free or Near Free tools on the Compiler side.

Debugging JTAG tools, FTDI have some parts that could be used to build up JTAG interfaces. Perhaps an open source debugger / JTAG chain?

I think Audio Processing on Cortex M4 is an interesting place to get audio hacking started to use ARM Cortex devices as a lower performance DSP/ Embedded microprocessor.

Several Cortex M4 suppliers to choose from and all have their merits and support in the Arduino camp. Much collateral to start to leverage from.

Hardware:

 the ToneCore pedal could be retasked to use a Cortex M4. Currently it uses a Freescale 9S08J64 for USB/ MCU and a DSP56364 for DSP functions. I have a good deal of the original material and we might be able to get Marcus Ryle to sell us some Tone core kits to retask to our needs. I'll send him a note and see what he says and get back to this list.

Dr. Beckmann has built up some great tools and perhaps a version could be crafted to be made available at a reduced price. 
Dr. Beckmann was correct to suggest 44.1 KHz as a target frequency.

What about a Stereo In and Out like the ToneCore unit?

General Midi could be supported via the USB and for software flashing into the memory.

I just don't want to steer this conversation to why the merits of a DSP.

The problem with the original ToneCore was it assumed people could program in assembly for the DSP56364. The Codewarrior tools supported the 9S08j64 with no real issue, but the Symphony Studio C Compiler does not really work well with 24-bit devices even though it is free and is still available.

I was plagued with calls on how to debug the DSP code and so on. Not a good place to start a Pedal Open source project.

Hopefully this steers the conversation back to your original intentions.

Thanks for all of your comments out there. Obviously some good replies and eager folks to get a project started.

 
Terry Shultz
DSP and ARM Audio Technology and Applications
thx1138 at earthlink.net



On Apr 24, 2013, at 7:50 AM, Martin Klang <mars at pingdynasty.com> wrote:

> hi hackers!
> 
> I'm involved with a project to build an Open Source, reprogrammable fx pedal based on the ARM Cortex M4 chipset.
> 
> The processor we have in mind is the STM32F405, which some of you on the list are very familiar with already:
> a 32bit powerhouse with built in DSP and floating point processing units.
> 
> We're planning to launch it on kickstarter, but we'd like to get some feedback from interested parties first.
> 
> We've got a preliminary spec sheet online, have a look and pls email me (or the list, if you think it is of general interest) with any thoughts, questions or ideas!
> 
> http://hoxtonowl.com/specification/
> 
> best,
> 
> Martin Klang
> Rebel Technology
> London UK
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> Synth-diy at dropmix.xs4all.nl
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