electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
Live streaming at radio.electro-music.com

  host / artist show at your time
<on air> Jez Adventures in Sound
Please visit the chat
 Forum index » DIY Hardware and Software » Developers' Corner
Simple DIY dsPIC Project
Post new topic   Reply to topic Moderators: DrJustice
Page 3 of 6 [147 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Goto page: Previous 1, 2, 3, 4, 5, 6 Next
Author Message
Blue Hell
Site Admin


Joined: Apr 03, 2004
Posts: 20697
Location: The Netherlands, Enschede
Audio files: 156
G2 patch files: 318

PostPosted: Sun Apr 17, 2011 8:31 am    Post subject: Reply with quote  Mark this post and the followings unread

JovianPyx wrote:
Ok, here is the Mozart piece.


Nice one Scott!

_________________
Jan
Back to top
View user's profile Send private message Visit poster's website
emeb



Joined: Dec 16, 2008
Posts: 27
Location: Arizona

PostPosted: Sun Apr 17, 2011 9:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,

I've been lurking on this thread for a while and thought I'd throw out a few comments:

* First, kudos to Scott. He does amazing things with FPGAs and I'm looking forward to what he can do with a dsPIC.

* For what it's worth I've got a bunch of dsPIC and FPGA related projects documented on my website here:

http://members.cox.net/ebrombaugh1/synth/index.html

Schematics, PC boards and source code included for most of them.

* It's worth noting that several of the dsPIC designs at the site linked above are the basis for the Synthesis Technology E3x0 and E5x0 series of Eurorack modules. I did a lot of the software prototyping on these little boards before we went ahead with the form/fit/function development. Based on my experience with those modules, the direction you're going using dsPICs in this thread seems feasible.

* Sample rates for the '802 DAC - The clock rate for the on-chip DAC is closely tied to the rate that the processor runs, although there is some flexibility due to the various dividers in the clock generator. In some of my oscillator applications, I usually run the dsPIC CPU at about 39MHz and then run the DAC at about 98kHz - this seems to give a good balance of sample rate vs processing throughput. For audio effects the sample rates don't need to be as high because you're not as worried about aliasing, so those will typically run the CPU at 23 or 39MHz and then clock the DAC in the 30 - 40kHz range.

* Programming language: MCHP has a decent (not *great*) C compiler for the dsPIC available for free. It integrates nicely with MPLAB and I've had pretty good luck using it for some of my more recent projects. You don't want to try using it to do high-performance DSP coding, so I use assembly for that, but I've found it works nicely to code interrupt service routines which handle signal processing in assembly, and then the low priority 'big loop' code for housekeeping works fine in C. I also have had good luck building up a personal library of C callable assembly functions for common calculations, like exponential conversion, filtering, nonlinear functions, etc. Also, parsing MIDI in C is worlds easier than trying to do it in assembly...

* Someone mentioned that the DACs can be noisy. True. Also from time to time you may come across a dsPIC with bad DACs. I've got no idea how those slip through the manufacturing testing process, but usually just swapping them out works.

Keep up the good work. I'll be lurking so if there's any way I can contribute just gimme a shout...
Back to top
View user's profile Send private message
loss1234



Joined: Jul 24, 2007
Posts: 1535
Location: nyc
Audio files: 41

PostPosted: Mon May 09, 2011 12:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

I will be watching this post with excitement! I would love to find a SIMPLE SDIY DSPIC project!

I have been finding tons of synth related AVR projects...But everyone keeps telling me the DSPIC has the power to do amazing things...sadly, unlike the AVR, it seems much harder to find projects to learn from, and the code seems more complicated...(hence the need for projects to learn from Wink


anyway, thanks for doing this!

_________________
-------------------------------------------- check out various dan music at: http://www.myspace.com/lossnyc
http://www.myspace.com/snazelle
http://www.soundclick.com/lossnyc.htm http://www.indie911.com/dan-snazelle
Back to top
View user's profile Send private message
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Mon Nov 07, 2011 5:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've added DDR SDRAM to the FPGA design for this. 41+ seconds of delay.

I also bought some Microchip 23K256 ICs, these are 32K byte SPI SRAM ICs. Using the CS pin to select the RAM being accessed, I should be able to put 2 of them on the SPI port of the dsPIC and have 32K words for a 740 mSec delay at 44.1 kHz sample rate. This lives all of the internal dsPIC SRAM free for DSP magic.

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Tue Sep 18, 2012 1:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

I now have a working dsPIC bench-test environment board. It has power supply, 3.3v reg, LED (top row left) input power connector, 6 pin RJ11, 28 pin socket for dsPIC and all support circuitry. It needs only be connected to a programmer such as PICkit-2.

I've just tested it at 40 MIPS with a 20 MHz crystal. I followed rule of thumb RF technique of keep the wires as short as possible. One of the capacitors is actually on top of the crystal with short spaghetti to keep from shorting on the xtal can.

There is a LED (bottom row center) with 200 ohms on pin 21 which is RB10. This is here for testing and experiments.

This is mainly a programmer, the application will be on it's own board without the programming hardware.

Thank you to Tom Wiltshire.


dsPIC_DIY_Programmer_and_Testbench.jpg
 Description:
dsPIC DIY Programmer and Testbench
 Filesize:  48.37 KB
 Viewed:  186 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

dsPIC_DIY_Programmer_and_Testbench.jpg



_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
Dan Lavin



Joined: Nov 09, 2006
Posts: 620
Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Fri Sep 21, 2012 1:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

Scott: this is still the flute you're porting over to the dspic, correct?
_________________
Synth DIY since 1977!
Back to top
View user's profile Send private message
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Fri Sep 21, 2012 2:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Actually, no, I'm being more adventurous. This will be a 3 dsPIC project that will hopefully be a 12 voice Karplus-Strong harp synth.

I have the MIDI hardware working along with a TTY port, I can so far send the hex value data from MIDI messages to a UART/TTY output which I connect a COM port on my PC.

This will soon turn into a MIDI controller (I have PicoBlaze uC code I can convert).

Trying to get the MIDI UART to interrupt...

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Tue Sep 25, 2012 7:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've now got a board that can receive MIDI data on one port and send the same data at 115.2 kilobaud to a PC COM port. The MIDI receive stream is interrupt driven. The application reads MIDI bytes and translates them to hex ASCII characters sent to the output UART.

Thank you to Blue Hell.

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Fri Oct 05, 2012 6:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

Second board is partially built and tested. The board will eventually have 2 dsPICs. Currently, one is installed and working at 40 MIPs.

The socket on the right side of the board is for the other dsPIC.

The power supply generates 3.3v and +8 volts. I just got the -8 volt regulators today. +/- 8 volts will power an opamp.


P1010375.JPG
 Description:
Stripboard dsPIC project
 Filesize:  120.51 KB
 Viewed:  183 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

P1010375.JPG



_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
Dan Lavin



Joined: Nov 09, 2006
Posts: 620
Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Fri Oct 05, 2012 7:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

So even with 3 dsPICs it looks like a low parts count, or maybe I'm just wishful thinking here!?
_________________
Synth DIY since 1977!
Back to top
View user's profile Send private message
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Fri Oct 05, 2012 8:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

My hope is to get 8 voices minimum out of the synth. In this case, one dsPIC will be a MIDI controller and voice assigner, the other 2 will be voice engines.
_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
Cynosure
Site Admin


Joined: Dec 11, 2010
Posts: 716
Location: Toronto, Ontario - Canada
Audio files: 42

PostPosted: Fri Oct 05, 2012 8:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

It looks like it is coming along well. I can't wait to hear it!
Back to top
View user's profile Send private message
bubzy



Joined: Oct 27, 2010
Posts: 558
Location: United Kingdom
Audio files: 63

PostPosted: Sat Oct 06, 2012 3:51 am    Post subject: Reply with quote  Mark this post and the followings unread

looks like an arduino would be neater
*hides*

_________________
_Richard_ Smile
Back to top
View user's profile Send private message
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Sat Oct 06, 2012 5:35 am    Post subject: Reply with quote  Mark this post and the followings unread

Probably would be neater, but then it would be dsPICable. And just think of all those MIPS...
_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Thu Oct 11, 2012 3:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

I now have 2 dsPICs running at 40 MIPS with a 10 megabit per second one-way SPI link between them.
_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
Dan Lavin



Joined: Nov 09, 2006
Posts: 620
Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Thu Oct 11, 2012 6:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

Good job, Scott. I'm guessing this is the hard part and it's all downhill from here....or am I being overly optimistic? Wink
_________________
Synth DIY since 1977!
Back to top
View user's profile Send private message
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Thu Oct 11, 2012 6:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

Dan Lavin wrote:
Good job, Scott. I'm guessing this is the hard part and it's all downhill from here....or am I being overly optimistic? Wink


The dsPIC SPI module was designed to be versatile enough to connect to any sort external SPI device that can run at 10 megabits per second or less. This means the module accepts many parameter choices - all of which have to be correct or it won't work. I was also a bit worried about the electrical end of things. 10 megabits per second is essentially RF and as such, RF practices need to be observed. Clock and data lines should be the same length - but not too long. Under some conditions, buss termination resistors might be required (for long wires). Fortunately, it works with an 11 inch cable and no termination resistors. The signals (clock and data) look very clean and crisp on an oscope.

So for me, this was a big deal and yeah, it should be easier here on out.
Next is to get the DAC making a signal.
After that to get the ADC to acquire CVs from dsPIC pins.
And finally, I get to write the synthesizer. Smile

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
Dan Lavin



Joined: Nov 09, 2006
Posts: 620
Location: Spring Lake, Mi, USA
Audio files: 21

PostPosted: Thu Oct 11, 2012 7:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
After that to get the ADC to acquire CVs from dsPIC pins.
Is this for knob tweaking of timbre parameters or 1V/octave pitch control like an analog synth? I guess I figured it would be midi controlled, but hey whatever!
_________________
Synth DIY since 1977!
Back to top
View user's profile Send private message
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Thu Oct 11, 2012 7:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

This first project will be a MIDI controlled polyphonic harp synth based on Karplus-Strong string models. Two parameters that affect the synth's timbre are the loop's lowpass filter cutoff frequency and a linear damping value. These two parameters will be set by pots (supplying the CVs to the dsPICs). It could easily be modified to accept CVs generated by other devices. I am also considering a module that will accept an additional CV for pitch. In the modular version, the pitch CV would be captured and stored when the trigger occurs. Because it will have a sustain pedal input, it would be possible for a modular owner to use a sequencer to play the harp - even in polyphony because of the sustain pedal. Chords could be played with a sequence of pitch-change and triggers that are closely spaced in time. I will have to talk with modular friends to determine if this is feasible with the kind of equipment that they already own, so at this point the module version is only an idea.
_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Fri Oct 12, 2012 1:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Data reliability test passed.

The test was designed as follows:

A transmit dsPIC was programmed to generate a 16 bit pseudorandom number using a 32 bit LFSR. The low word is used as data. The 32 bit SPI message was create using the low word and it's ones complement. This is then sent to the receiver with 1 uSec of dead time between transmissions.

A reciever dsPIC was programmed to receive the 32 bit messages (using interrupts). The received 32 bits of data is loaded into 2 registers. One of the registers is ones complemented and the two are then compared. If equal, the transfer was good. Errors cause a period to be sent to a terminal session using a UART set at 115.2 kbaud. As long as the terminal session has a blank screen, everything is fine. I tested the system by running it for awhile noting the blank screen. If the SPI connection is disconnected and reconnected, I get dots.

Both dsPICs were run at 40 MIPS with SPI set for 10 megabits per second.

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Mon Oct 15, 2012 9:56 am    Post subject: Reply with quote  Mark this post and the followings unread

During my testing of SPI reliability, I found that a flourescent work light near the boards would cause SPI errors when switched off. I will add termination resistors to hopefully abate that behavior.
_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Mon Oct 15, 2012 2:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

After reading about termination, I decided on 1K resistors to ground and +3.3 on both SCK and SDI. The resistors are on the receiver end of the cable.

When testing after I added these resistors, the errors generated by turning off my flourescent work lamp stopped. I do not know if this termination will work in other environments. From what I've read, 1K is a rather light termination. I want the current as low as possible.

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
Blue Hell
Site Admin


Joined: Apr 03, 2004
Posts: 20697
Location: The Netherlands, Enschede
Audio files: 156
G2 patch files: 318

PostPosted: Tue Oct 16, 2012 7:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Ideally termination is on both sides and has the same impedance as your cable ... a twisted pair cable impedance calculator :: http://www.eeweb.com/toolbox/twisted-pair . It'll all be a bit of an approximation of course, when your cable is shorter than about lamba / 6 it should not matter too much anyway ... hmm10 MHz is 30 meter or so ... so for cables over about 5 meter it might become an issue.

Two times 1k means 500 Ohm termination, which is not really that high I think.

_________________
Jan
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Tue Oct 16, 2012 7:50 am    Post subject: Reply with quote  Mark this post and the followings unread

As I said, my termination is light and doesn't represent a "fix all" for all environments. Readers should not take it as the absolute best solution, only that it worked for me in my lab.

Since the SPI signals look very clean on my oscope (no reflection that I can see), my intention was mainly to surpress external noise effects, which apparently it did. My reading regarding termination would have put the resistors at around 270 to 330 ohms, but I didn't want that much current if I can help it.

In reading about SPI in particular, most opinions were that no termination is necessary at all given a short enough transmission line. 11 inches is considered quite short at 10 MHz and it ran fine with no termination - as long as I didn't turn that flourescent lamp off. Also, the SPI articles I read did not mention using termination at both ends (as is the case for a bus like DEC's Unibus - but this is an open collector bus). I did think that was odd, but went with a terminator at the receiving end only (as was described in several articles). I looked at the schematic for the Spartan-3E Starter Board (FPGA) SPI circuit which is spec'd to run at 50 MHz and has 100 ohm termination resistors to both rails at one end only. Works quite well.

There are many factors to consider with transmission lines, length being one of them. I do understand the theory, and surely a best effort terminator may well be at both ends and a much lower resistance, especially for a more significant length of wire - however, what I did works.

As always, your particular milage may vary. If you play with this stuff, you may indeed need heavier termination than I used.

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
JovianPyx



Joined: Nov 20, 2007
Posts: 1252
Location: West Red Spot, Jupiter
Audio files: 161

PostPosted: Thu Oct 18, 2012 12:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's the state of the lab. The two pots supply CV values to two pins on the dsPIC. I am currently working on getting the ADC to read the pot voltages.

Currently, I have MIDI, SPI and DAC working. ADC is the last of 4 elements I need for this synth before actually coding the synth.


2012_10_18_P1010388.JPG
 Description:
Current state of my dsPIC lab.
 Filesize:  192.34 KB
 Viewed:  175 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

2012_10_18_P1010388.JPG



_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic Moderators: DrJustice
Page 3 of 6 [147 Posts]
View unread posts
View new posts in the last week
Goto page: Previous 1, 2, 3, 4, 5, 6 Next
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » Developers' Corner
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use