Simple DIY dsPIC Project

JovianPyx · Posted: Sun Nov 11, 2012 11:21 am Post subject:

The last sample has clipping. The clipping came from the output amp having too much gain. This sample is the same piece, but played on the synth with lower gain and the clipping is gone.

My_Brain_Is_An_Electron.mp3

Description:

My Brain Is An Electron

Filesize:

1.49 MB

Duration:

1:38

Viewed:

2452 Time(s)

JovianPyx · Posted: Sun Nov 11, 2012 5:04 pm Post subject:

Here's a sample of what it might sound like to have 2 Harpies. I generated a recording of this sequence and then again at an octave higher. I offset the higher one in time from the lower one by some milliseconds and made this mix in Audacity.

Sometimes_I_Repeat_Myself.mp3

Description:

Sometimes I Repeat Myself

Filesize:

2.36 MB

Duration:

2:35

Viewed:

2482 Time(s)

Cynosure · Posted: Sun Nov 11, 2012 5:45 pm Post subject:

It sounds awesome. Amazing job!

JovianPyx · Posted: Tue Nov 20, 2012 3:14 pm Post subject:

I have two more samples. They are both from a MIDI file I adapted for the Harpie.

One has the reflection filter Fc low, the other has the setting higher.

The piece is "Entry of the Gladiators" by Julius Fucick. Many of you will recognize it. I was playing different MIDI files through the Harpie and twizzling the timbre knobs and I like the way it plays this. If you listen, I hope you like these.

Fucick_Entry_of_the_Gladiators_lower_filter.mp3

Description:

Lower reflection filter setting
Entry of the Gladiators by Julius Fucick

Filesize:

2.74 MB

Duration:

2:59

Viewed:

2337 Time(s)

Fucick_Entry_of_the_Gladiators_higher_filter.mp3

Description:

Higher reflection filter setting
Entry of the Gladiators by Julius Fucick

Filesize:

2.76 MB

Duration:

3:01

Viewed:

2299 Time(s)

elmegil · Posted: Tue Nov 20, 2012 7:52 pm Post subject:

Got any Scott Joplin files? Very Happy

That sounds awesome. I know, I need to find a new adjective.

JovianPyx · Posted: Fri Nov 23, 2012 9:15 am Post subject:

I would like to thank Tom Wiltshire (who may be a member here) and Blue Hell for their help in getting things started up with dsPIC development.

elmegil · Posted: Fri Nov 23, 2012 9:20 am Post subject:

And thank you for documenting your steps, so there's a chance some of us might follow (eventually...backlog.... Smile

)

blue hell · Posted: Fri Nov 23, 2012 12:30 pm Post subject:

Glad I could help Scott, you're doing great stuff with it!

JovianPyx · Posted: Mon Nov 26, 2012 4:41 pm Post subject:

I've built another DIY stripboard dsPIC with a Microchip 23K256 SPI SRAM. This is a 32 kilobyte SRAM organized in bytes. I connected the SRAM to the dsPIC with 2.5 inch wires and used no termination. The SPI SRAM operates nicely at an SPI data rate of 10 megabits per second (max for the dsPIC).

One thing I discovered is that the SRAM bar-CS pin cannot be tied low to force the IC to always be selected. The documentation could be a bit more clear about the actual function of bar-CS. They call it "chip select" which indeed it is, but it also serves to terminate the previous command. If bar-CS is simply help low, the SRAM does not function correctly. Each full transaction to or from the SRAM requires:

1) Bring bar-CS low
2) Send command
3) If write, send data. If read, accept the read data
4) Bring bar-CS high

In the documentation it is mentioned that bringing bar-CS high terminates the previously executed command. It does not clearly state that each SRAM transaction must be bracketed by a bar-CS low and bar-CS high. When bar-CS is low, it selects the SRAM and causes it to enter command mode. When bar-CS is raised, the SRAM terminates whatever it was doing (which is fine if it is timed so that the previous transaction is fully completed).

EDIT ADD:
In order for read from SRAM operations to be successful, it is necessary to make sure that the data being read from the SRAM SDO pin remains synchronized at all times. The dsPIC will shift data on SDI in whether it is a read operation or not. It is up to the driver to figure out how to do this. In my simple test program, I just wrote code to read the buffer register for each byte written to SDO. Most of these are dummy reads, but they keep the register synchronized so that when the real read data is there, it can be read out of the register. This is a bit confusing because one might think that if they are in the process of sending command data to the SRAM, then there's no valid data to read - and that is true, but if the dummy reads are not done, the SPI overrun indicator bit is set and further attempts to read the SDO line will fail. I am now looking into using DMA so that perhaps I can avoid using up CPU cycles to manage these reads. If the reads can done by the DMA controller, then this is work that gets done "for free" so to speak. (I do hope this last paragraph makes sense, it's late and I'm very tired, but wanted to add this information).

JovianPyx · Posted: Tue Feb 12, 2013 3:59 pm Post subject:

Here is a sample of an experiment I did in C that I wish to apply to the Harpie synth. It is a bowing algorithm. In the sample, what you hear is an arpeggio that is repeated several times. Each time it repeats, the reflection filter for the karplus-strong system is "opened" allowing more high frequency energy to be retained. The model I developed allows control over the bow speed, bow pressure and KS reflection filter cutoff. In the Harpie hardware, the filter would be controlled by a pot. Bow pressure would be controlled by channel pressure and bow speed by modultion wheel.

karplus-strong_bowing_algorithm.mp3

Description:

bowing algorithm test from C program

Filesize:

638.85 KB

Duration:

0:41

Viewed:

2234 Time(s)

JovianPyx · Posted: Mon Jul 29, 2013 2:53 pm Post subject:

Been a long time since I've added anything.

I've made a simple synth board with a dsPIC33F (28 pin DIP), 2 TL074 and 1 6N138 to make a MIDI synth. I'm using both ASM30 and C30. Some of the synth components are coded in assembly language and all of the synth logic is written in C.

Currently, the synth consists of 2 oscillators, each oscillator drives 2 wavetables. the 2 wavetables are sinewave and distorted sinewave. Velocity pan-interpolats between the two tables. The 2nd oscillator is tuned an octave above the first and is more prominent with stronger velocity. The result is a fairly convincing flute sound. It seems that I have more CPU power (about 100 free CPU cycles), so I will add some noise for a bit more fun.

Dan Lavin · Posted: Mon Jul 29, 2013 6:07 pm Post subject:

Cool Scott! Hopefully you'll post the code when complete. This sounds like it would make a nice addition to my studio! Very Happy

JovianPyx · Posted: Tue Jul 30, 2013 3:50 pm Post subject:

Hi Dan,

As much as I have enjoyed posting such details in the past, I am seriously considering moving my projects into a commercial realm, so I really cannot publish the full details of this.

I would like to make this project and others like it available to people at a fair price, that being one that contains the cost and also compensates me (to some small degee) for the work I put into it. I am considering a range of options including, bare boards, assembled boards, assembled boards with a pre-programmed dsPIC IC as well as just the pre-programmed dsPIC IC.

Right now this is in the "proof of concept" stage. The testing has shown that I can embed a MIDI controller in the dsPIC along with a voice engine and the two seem to play nicely together. I am not finished with all of the "what if" stuff yet, but soon. What I have at this point is a basic functional synthesizer that sounds pretty good. I plan to post some sound samples when I get the design more complete.

Dan Lavin · Posted: Tue Jul 30, 2013 7:21 pm Post subject:

That's fine Scott! I certainly don't mind paying for it. I've done that with my Shruthi, Sammich FM, bass boy and a few more things. A flute-like synth would be cool for the home studio!

JovianPyx · Posted: Wed Jul 31, 2013 4:56 pm Post subject:

Here is a sample of what is currently developed for my Additive Flute Synth.

I processed the dry synth signal with some Audacity gverb.

All of the timbre control so far is velocity. I have plans for more and better control. Currently the synth operates at 89 kHz.

dsPIC_Additive_Flute_Model_demo_000.mp3

Description:

Some note diddles on my Additive Flute Synth (single dsPIC).

Filesize:

2.33 MB

Duration:

2:33

Viewed:

2371 Time(s)

JovianPyx · Posted: Thu Aug 01, 2013 4:55 pm Post subject:

Please note that the above sample has some rather generic settings. This is also a "budding prototype". When I did the sample I was excited that the damn thing worked at all and just did some crazy numeric trimming to get what is in the mp3. I've been told that the sound has too much "chiff" from the noise generator. This makes it sound a bit like a pipe organ thing.

I plan to have 4 pots to control how things are mixed, chiff amount would be one of those things. Such a set of controls would allow more control over exactly how this sounds. The pot inputs are already wired, I just need to buy some pots and wire them up.

Still a work in progress...

elmegil · Posted: Thu Aug 01, 2013 6:44 pm Post subject:

I did get the sound of pipe organ out of several bits of it, but it still sounded cool. As far as "chiff" goes, I'll call that my vocabulary word for the day Very Happy

JovianPyx · Posted: Thu Aug 01, 2013 7:44 pm Post subject:

Well, none of that sounds bad at all. This (so far) is a very basic design and I plan much more user control over the sound. I call it a flute synth, but I'd prefer it to wind up being a pipe synth, as in lots of different pipes. One of the knobs will control the amount of "chiff", another will probably control the amount of sine versus sine plus 2nd and 3rd harmonics. another knob may control the timing of the ADSRs.

At the moment I'm working on portamento and pitch wheel. Still deciding how to implement mod wheel.

JovianPyx · Posted: Mon Aug 05, 2013 3:12 pm Post subject:

I've made some good progress. I've added (at least) portamento, pitchwheel and other changes.

The attached piece is just me playing a keyboard using the mod wheel as an expression tool (as well as velocity) and the right hand is trying to play melodies.

I try to "express" in the piece, as if the flautist were blowing harder and softer in an enveloped LFO fashion.

dsPIC_Additive_Flute_Model_demo_001.mp3

Description:

Single dsPIC MIDI Synthesizer (Additive Flute Model) demo 001

Filesize:

2.33 MB

Duration:

2:33

Viewed:

2289 Time(s)

blue hell · Posted: Wed Aug 07, 2013 6:07 am Post subject:

Sounds good to me.

JovianPyx · Posted: Mon Aug 19, 2013 5:15 pm Post subject:

Here is another piece of music as a demo. It uses the single board flute synth with the Ninja Harp (also called Harpie). The flute is a monosynth using a single dsPIC33F. The Ninja Harp is an 8 voice polysynth using 3 dsPIC33F ICs.

The music is a sequence played by Cakewalk. During the sequence, I "play" the two knobs on the Ninja Harp (which are Damping and Lowpass Cutoff) which gives the very obvious timbre changes you hear. Since these are pots, their performance data is not recorded as MIDI information.

10230818.mp3

Description:

Ninja Harp and Jovian Floot

Filesize:

2.03 MB

Duration:

2:13

Viewed:

2365 Time(s)

Cynosure · Posted: Mon Aug 19, 2013 5:23 pm Post subject:

Awesome song. I love the variations that the harpie does.

JovianPyx · Posted: Mon Aug 19, 2013 6:21 pm Post subject:

Here's another take - this time I used the portamento ability of the floot.

10230818a.mp3

Description:

Ninja Harp and Jovian Floot (with portamento)

Filesize:

2 MB

Duration:

2:11

Viewed:

2325 Time(s)

JovianPyx · Posted: Mon Aug 19, 2013 6:44 pm Post subject:

I will leave you with this -- a mix of both of those tracks Smile

10230818_both_1.mp3

Description:

Both

Filesize:

2.03 MB

Duration:

2:13

Viewed:

2385 Time(s)

JovianPyx · Posted: Tue Aug 20, 2013 6:53 pm Post subject:

Spent more time on the mix... I like this one better...

10230818_both_3.mp3

Description:

Ninja Harp and Jovian Floot

Filesize:

2.03 MB

Duration:

2:13

Viewed:

2358 Time(s)