Author Topic: DSP for detuning  (Read 4157 times)

swinginguitar

DSP for detuning
« on: October 21, 2011, 11:56:57 AM »
Is there a DSP out there that would do detuning (like say +/- 1 to 12 cents) ready to go with minimal fuss getting it into a circuit (preferably with on-board or easily integratable ADC/DAC)?

Would like to add stereo detuning to a project...

octfrank

Re: DSP for detuning
« Reply #1 on: October 21, 2011, 12:43:21 PM »
The Spin FV-1 is the only one I can think of, and not just because my company is the distributor but I really can't think of another DSP with a pitch shift program built in along with ADC and DAC in stereo. See the data sheet http://www.spinsemi.com/Products/datasheets/spn1001/FV-1.pdf The shift program built in is +/- 4 semitones but if you want to limit it to +/- 12 cents then you can mod the code an burn it to an eeprom that the FV-1 can read from.
Frank Thomson
Experimental Noize

swinginguitar

Re: DSP for detuning
« Reply #2 on: October 21, 2011, 02:54:04 PM »
That's what I'm looking for

however

I may have to put it on the backburner since I'm knee deep in PIC code right now and will have to defer learning enough about DSP to do this until I have more time to throw at it.

Otherwise, that's pretty much a turnkey solution.

How difficult would it be to code it for +/- cents and have the left and right signals independently configurable? And also, can you have an overall mix knob?


octfrank

Re: DSP for detuning
« Reply #3 on: October 21, 2011, 03:55:19 PM »
There are docs on how to write the pitch shifting code and the equations used to calculate the pitch amount at the Spin site so it is rather simple if you understand basic programming concepts.

The 3 POT inputs can be used for anything basically so you could do left and right independently and mix as well or mix externally.
Frank Thomson
Experimental Noize

swinginguitar

Re: DSP for detuning
« Reply #4 on: October 21, 2011, 05:13:55 PM »
Do I need any gear to flash the DSP, or just flash an eeprom and the DSP will read it as is?

Is there a list of compatible eeproms in the docs somewhere?

octfrank

Re: DSP for detuning
« Reply #5 on: October 21, 2011, 05:23:12 PM »
Just flash an eeprom, a 24LC32A.  The SpinAsm assembler is free on the Spin site and will produce an Intel HEX file for device programmers.

Set the FV-1 to external mode (just a pin on the chip), connect the serial clock and data pins between the FV-1 and eeprom and it will read the programs from the eeprom. You can have up to 8 programs in the eeprom, SpinAsm will assemble and build them into a single HEX file.
Frank Thomson
Experimental Noize

swinginguitar

Re: DSP for detuning
« Reply #6 on: October 24, 2011, 09:45:04 AM »
I see that the 24LC32A is on the compatibility list for Pickit 2. I've never done an EEPROM before - is there any documentation out there on which pickit pins go to which eeprom pins (and any other circuitry involved) for flashing those? the eeprom datasheet wasn't too helpful....

Also, does that DSP have enough power to run the detuners as well as a short (<150ms) pre-delay on each side?

slacker

Re: DSP for detuning
« Reply #7 on: October 24, 2011, 12:52:00 PM »
Here's a schematic for programming the eeprom, Pin 1 on the programmer is the one marked with the white arrow.



47k might not be the best resistor value but it works for me.
If you need any more info there's a "README" file on the Pickit Starter CD that explains how to hook it up to all the supported chips.

Quote
Also, does that DSP have enough power to run the detuners as well as a short (<150ms) pre-delay on each side?

Yeah, it will be able to do that.

swinginguitar

Re: DSP for detuning
« Reply #8 on: October 25, 2011, 02:07:55 PM »
Awesome! Thanks everyone.

OCTFRANK: any of the major electronic suppliers (local or mail) sell these?

octfrank

Re: DSP for detuning
« Reply #9 on: October 25, 2011, 03:54:39 PM »
OCTFRANK: any of the major electronic suppliers (local or mail) sell these?

No but we do sell direct to end users, email me at frank (at) oct-distribution.com with the quantity, shipping address and shipping method (USPS, UPS ground, FedEx, etc.) and I'll get an invoice to you with the total. We accept PayPal so no need to email or call with credit card, with the invoice will be our Paypal payment address.
Frank Thomson
Experimental Noize