Jump to content

porting parts of MIOS to a dsPIC ?


ztutz
 Share

Recommended Posts

I'm looking at using a dsPIC 30F6014 as the core of a small special-purpose single board synth, and I'm wondering whether the code for MIOS would be a good place to start for the tools and control side of things. The synth would have control surface demands not unlike a MIDIbox, although the UI might be a bit wackier than some.

Seems to me that the bootloaders and sysex comm/dump stuff, along with the support for AIN, DIN, DOUT, and possibly AOUT boards could potentially be reused. But rather than converting control movements into MIDI, this box would take the values and use them as parameters while performing DSP synthesis algorithms (and then shipping the results off to a DA converter -> an amp -> and a speaker....)

I'm not yet sure whether the dsPIC is up to overall size of the task, nor am I sure that it is architecturally close enough to the 18F452 to make porting the right thing to do, nor am sure that I have the expertise to pull this off, but before I do the big investigation, I'm curious whether people think that this would be an appropriate thing to do with the MIOS code.

This would be a non-commercial project, of course. A DIY digital synth, similar in spirit (if not implementation) to the AVRSynth or other such projects. The other construction option is to build it from a small form factor PC board, but that seems like a far less entertaining construction project!

Anybody got input for me? Thanks!

Link to comment
Share on other sites

Hi,

I took a look at both the dsPIC and the PIC24H chips and they are pretty much the same except, of course, the dsPIC has the DSP engine. Porting MIOS to either of these chips certainly looks doable. However, since these chips have a richer instruction set I would seriously consider a new design for the firmware that takes advantage of things such as 16 bit data memory, a true hardware supported software stack, 16 working registers etc.

Take a look at the new Explorer 16 demo board on the Microchip website for the PIC24. One board comes with both a dsPIC and a PIC24 chip so that experiments could be done on both to determine which might be most appropriate for a particular application. And, considering that the board supports USB, RS232, LCD and more, it is relatively inexpensive, only $129 USD.

Keep in mind that these chips come in surface mount packages only. This presents a challenge if you plan on building your own circuit boards.

Regards,

Synapsys

Link to comment
Share on other sites

Thanks for the replies.

I agree that from the perspective of MIOS as a general purpose platform, the PIC24 would make a lot of sense. However, for what I'm thinking of doing the DSP functions would be invaluable, since the synth code that I'd be executing is essentially a wad of vector math, filtering, and DFT stuff. Is anyone thinking about moving MIOS to the 16 bit PIC processors anytime in the near future?

Even with the DSP ops in the 30F, I'm a little worried that the timings might be too slow for my purposes. I'm not sure; I need to experiment or simulate a little to find out. A single sample of a mono CD-quality signal takes 22 microseconds, which means that you've got to be pretty quick about your math in order to do interesting stuff *and* also process your inputs and outputs. I took a look at the published timings for the Microchip DSP functions, which seemed to imply that these operations would suck up a significant chunk of my overall processor cycle budget.

I've had a chance to look over MIOS as well as the dsPIC stuff a little more - seems as though the bootloader and in interop with the DIN, DOUT, and AIN boards would be the most useful for my application. My analog out is very application specific: one or two channels of 44.1K sound. However, since timings are tight, I may be forced to write something very specific to my app; I can certainly learn from what the MIDIbox community has done even in this case!

--z

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
×
  • Create New...