Silicon Chip (Magazine) Digital Effects Processor

[cps]

Hi Folks,

I recently picked up the latest issue of Silicon Chip (AU) magazine. It contains a project for a digital effects processor that can do most of the standard processing tasks. It's based around a WM8731 and a PIC32MX470. The October issue of the mag doesn't seem to be available online yet (see <http://www.siliconchip.com.au/Issue/Browse>. I imagine it will appear soon. Anyway, I thought people here might be interested.

Cheers,

Chris

[Ice-9]

Thanks for the link to the magazines, I was just thinking the other day that you never seem to be able to find electronics project magazines anymore (like Practical Electronic Mag). Then I see this post, I had a quick flick through the contents of the mags there and they seem to have some interesting projects in them but you do obviously have to pay to view the whole contents of the magazine.
When it shows online for this months mag I may just have to buy it for that DSP effects project. 

[slacker]

Sounds interesting, I'm currently working on something similar, those cheap audio codecs are pretty cool bits of kit.

[g_u_e_s_t]

yeah, im definitely interested in checking out the schematic.  the online preview showed a pcb, but i couldnt see any opamps for input signal buffering.  there was also an unpopulated SRAM footprint.

i often wonder why the wm8731 is so popular.  even back in 2010 when i first started looking into this stuff, it had a lot of buzz on various forums.

[Ice-9]

Great, the preview wasn't there when I looked earlier. It is now and looks interesting, I'm not familiar with the PIC and other chips in the design but it seems the design in the magazine is restricted to 2 pot controls for parameters but I look forward to having a closer look at the schematics soon, maybe more control can be coded into the unit.

[slacker]

As there's no other chips on the board apart from the PIC and the codec they must be using the PIC's ADC to read the pots, so from a hardware point of view you can can add as many extra pots as there are spare analogue inputs, should be some left what with all those connections to the unpopulated RAM. Depending on how they are reading the pots in software it might be a trivial change or a complete rewrite of that part of the code.

It's using the same board as previous projects from Feb 2014 and Nov 2013, designed for PA/mixer applications which probably explains the lack of buffers and other stompbox friendly stuff.

[Ice-9]

Well out of curiosity I bought that edition magazine for online viewing, the schematic is basic and is just using mono in/out.  I wasn't able to download the hex or source code, when you buy the mag you are meant to be able the hex and source but it doesn't seem to be there yet.

I had to laugh at the bit in the article where they say "We haven't used the external memory on the PCB because we couldn't be bothered to implement it in the code".

Out of interest and on a different DSP does anyone know if the Elektor magazine FV-1 project docs are still available (the one with the LCD). I never got around to reading that and it is no longer on the Elektor website.

[octfrank]

Ice-9: is this it? http://serwis.avt.pl/manuals/AVT5159.pdf

[Ice-9]

Ice-9: is this it? http://serwis.avt.pl/manuals/AVT5159.pdf

octfrank: Thanks that is a bit different to the elector one I mentiond from the pictures I could find of the Elektor BUT the one you posted is the one I was thinking of. Thanks for that link just need to brush up on my Polish now. 

[octfrank]

ice-9: try this one
http://www.elektor-magazine.com/en/magazine-contents/article.html?tx_elektorarticle_list[article]=19448&tx_elektorarticle_list[action]=show
Looks like the square brackets are causing trouble making it hot in the message so you will have to copy/paste it

[Ice-9]

octfrank,  I did get that page earlier but when a link is clicked on that page for the article and other links they are all 404's missing pages. I think I may have to subscribe and be an Elektor member first.

[cloudscapes]

Thanks for the tip!

I've been trying to interface an WM8731 to a pic for years (granted it was a PIC32 MX5, not MX4) and have had miserable luck. More because of my limited knowledge on advanced/framed SPI, than a problem with the codec chip.

[MetalGuy]

This is the article from Elektor:

http://dfiles.eu/files/ge1uv5k7c

Also in my FV-1 folder I have a folder with what should be FV-1 ASM files. Please check them out and let us know if this is really FV-1 code:

http://dfiles.eu/files/cxz2m29ii

By the way I had similar project 6 years ago but then nobody was interested:

http://www.diystompboxes.com/smfforum/index.php?topic=70381.0

[potul]

Sorry to revive this old thread... but when looking for something else I stumbled on the Elektor FV-1 project again, and I found where to get the data from:

-Files (including software and gerber):
https://www.elektormagazine.com/magazine/elektor-201009/19448

-Article:

https://archive.org/stream/ElektorMagazine/Elektornonlinear.ir2010-09#page/n29/mode/2up

In fact, here you have some elektor historical numbers. Not sure if legal download, it's from archive.org
https://archive.org/details/ElektorMagazine

[Blackaddr]

For guitar effects, the ,WM8731 is a truly excellent codec. If you design a good preamp in front of it, it is very low noise.

This thread is a little old and as a former PIC programmer, I can't imagine choosing a micro that is not at least an Arm Cortex-M4F.

The key to low noise digital guitar effects is the design of the PCB routing once you take care of separate analog vs digital supplies.

[fermick]

Hello guys, I have already built some pedals with fv1 and everything works perfectly and I build the effects with spinCad. But from what you posted I seem to be able to save pressets, would that be my biggest wish for a simpler way? I would not like to use display only 2 or 3 keys to save the parameters.

[grenert]

Sorry to revive this old thread... but when looking for something else I stumbled on the Elektor FV-1 project again, and I found where to get the data from:

-Files (including software and gerber):
https://www.elektormagazine.com/magazine/elektor-201009/19448

-Article:

https://archive.org/stream/ElektorMagazine/Elektornonlinear.ir2010-09#page/n29/mode/2up

In fact, here you have some elektor historical numbers. Not sure if legal download, it's from archive.org
https://archive.org/details/ElektorMagazine

The author of that article designed a number of very interesting projects, including a few effects projects.  I made the Propeller-based B3 organ and it's really very nice (to me, who has never played a real B3).  He used to have a website, but it is sadly no longer up.  Fortunately, it is captured on archive.org as well.  Check it out!
https://web.archive.org/web/20161210222813/http://bolltone.de/

[potul]

Hello guys, I have already built some pedals with fv1 and everything works perfectly and I build the effects with spinCad. But from what you posted I seem to be able to save pressets, would that be my biggest wish for a simpler way? I would not like to use display only 2 or 3 keys to save the parameters.

Up until now I've seen 2 ways to approach the "preset" problem:

1-Use a microcontroller to manage presets and use digipots or similar to control the FV1 parameters. You don't really need digipots, just a way to control voltage of the pot inputs in the FV-1
2-Use a microcontroller to manage presets and modify the memory where the programs are saved, so that when the FV-1 is reading the program, the parameters are updated. This gives you more than 3 parameters to play with, but it gets really tricky to implement.

Mat