cheap dsp

[Maneco]

interesting!

http://elm-chan.org/works/vp/report.html

[Mark Hammer]

Congrats on having your looper included in the looping article in the current Guitar Player.  They didn't really talk about it specifically but it was quite visible, smack in the middle of a pile of all the competition (Loop Station, Boomerang, etc.).

[Maneco]

Oh! i did not know (the magazine is not available here!) but i knew there was an article...

Thanks Mark!

BTW ,this new forum rules,many new things to learn and share...

Maneco

[Peter Snowberg]

Congratulations Manceo!, and thanks for the link too!

That's a GREAT link!

===========================

I have those very DRAMS for anybody who wants one. All you need to do is to send me a self addressed, stamped envelope. Send me a PM if you're going ot build this project.

[The Tone God]

Seriously.

Andrew

[Maneco]

i found incredible how much this guy does with such a minimum hardware ...except for the dram,everything is on board...a/d,and pwm as d/a...that sounds ok if done fast enough,which those tiny's are capable of...i'm fascinated too

[Transmogrifox]

The only thing that raised a question is that he alluded to a 16MHz clock, and 250kHz PWM.  He can't use any greater than about 62.5kHz PWM if he wants 8-bit resolution on the output.  The 38ksps rate is reasonable.  You could theoretically have one sample per PWM period, but you wouldn't get 8-bit res. on a 250kHz PWM clock...just aren't enough clock cycles in that period to produce 256 discretely different pulsewidths.

Still a cool thing to try.  I think I'll get a DSP demo board when I start doing DSP, though...I could do a lot more cool stuff.  I was pretty excited looking at ATMEL's new high performance DSP & supporting demo board they offer.  Unfortunately it is very likely that the demo board is better than $900, and the DSP alone is likely in the $150 range.

[Mark Hammer]

Oh! i did not know (the magazine is not available here!) but i knew there was an article...

Thanks Mark!

BTW ,this new forum rules,many new things to learn and share...

Maneco

Send me a PM and I will try and scan the article for you to see.  It's actually a whole article on guitarists who use looping as a major part of their style, not a "looper shootout" or review of equipment..

[Maneco]

Always generous,Mark,thanks again!

BTW here's an interewsting link to a programmer,that supports pics and AVR ,easy to build,easy software...i'm a PIC man,but i will order some attiny26's to play,and will build a programmer like this...

http://www.lancos.com/prog.html

here's Olimex version...

http://www.olimex.com/dev/avr-pg1.html

[Dave_B]

http://www.olimex.com/dev/avr-pg1.html

That's the one I built that eventually stopped programming chips.  Others have apparently used it with a lot of success, so take my experience for what it's worth.

[RaceDriver205]

Awesome, if I get this thing to implement pitch shifting for me Im going to be so pleased!
Only effect I havent got (all mine are DIY).

[Primus]

I love this concept because it is small, cheap, and requires a minimum of parts. Not more than a fuzz! If this were 16-bit or higher, it's something I could really jump on. Then add knob twisty function and I am very happy. I don't suppose this guy can do the cool reverb, hall, etc. effects on a dedicated DSP though...

[idlefaction]

The only thing that raised a question is that he alluded to a 16MHz clock, and 250kHz PWM.  He can't use any greater than about 62.5kHz PWM if he wants 8-bit resolution on the output. 

Another reason why AVRs are cool!  This one has a 'fast peripheral clock' which is a PLL fed by the system clock, that you can put a hardware divider into the phase loop.  So you can multiply the ystem clock for use with the PWM.  It's great on the 8-pin low-power units, you can run them at 1.6MHz and use Fck *16 = 25.6MHz for the peripheral clock, giving you 100kHz PWM.  :-)

HTH!

[RaceDriver205]

New info for an Old thread:
Unfortunately, the RAM used is no longer in production. Nor is anything with similar pinouts available (for me at least). This means that it will require either modifying to use a modern serial ram like the 24LC256, or my prefered way - use a bigger AVR.
Furthur, this means decyphering the code (which I am attempting, its not that thoroughly documented). I have never heard of using a PWM to act as a DAC, so I am not aware how this method works. I intend to try to alter the RAM read/write section only, as the code fortunately implements these steps in separate code procedures.
No one can tell me that a proper DIY Pitch Shifter would go amiss here. 

[Peter Snowberg]

I have those very DRAMS for anybody who wants one. All you need to do is to send me a self addressed, stamped envelope.

PM me your address and I'll send you a couple.    (they're even the ZIP package)

[RaceDriver205]

Serious! To have those, you must have been in this game a while, Peter. Thanks for the offer.
Given that there may not always be a kind person to deal out the RAMs though, and that ill have to modify it for a guitar-style effect, I'll work out a design for a 'modern' version. Then everyone will have access to the parts if they decide to make it in the future.
Thanks anyway.

[Peter Snowberg]

Serious! To have those, you must have been in this game a while, Peter. Thanks for the offer.

Yep.... long time. 

I remember when 16K*8 cost $270(US)

I actually have a few rails of those DRAMs that came from a discontinued military data logger at Ampex. They were clearing the stock room of "garbage" and I got lucky.

You could just use a big SRAM these days. A battery backup becomes an option then too.

[Michael Allen]

So what exactly do you have to do? You have to program the ATtiny26 right? How?

[Peter Snowberg]

So what exactly do you have to do? You have to program the ATtiny26 right? How?

You'll need to build one of these...

http://elm-chan.org/works/avrx/report_e.html

...or you'll need to buy a commercial equivalent like the Atmel AVR STK500, which is what I have. ($79 at Digikey )

If you get the ATtiny26 and send it to me, I'll be glad to program it and send it back with the DRAM.