[sdiy] Arpeggiator1 / Arduino UNO

[Roman Sowa]

How does your 8+8 bit PWM DAC perform in terms of DNL at the MSB 
boundary? I mean when for example it goes from 40FFh to 4100h, as well 
4000h to 3FFF.

Roman

PS. I put so many tehnical sounding mumbo jumbo in first sentence that 
it sounds even funny :)

W dniu 2015-04-10 o 01:03, Rick Jansen pisze:
> Hi all,
>
> Well, at long last I'm a bit back to synth-diy-ing. Here is my first
> Arduino UNO based project: an arpeggiator:
> <http://dropmix.xs4all.nl/rick/Emusic/Arpeggiator1/>
>
> It serves two purposes: 1. getting to know the Arduino, and 2. finally
> using that 1-octave piece of keyboard that was in a box for 20 years.
>
> It's still in the breadboard phase, as a tryout for the upcoming
> sequencer, but it works, and I'm having a lot of fun with it.
>
> A longer writeup, images and sketch are in the web page
>
>    <http://dropmix.xs4all.nl/rick/Emusic/Arpeggiator1/>
>
> Here are some keywords:
>
> - I2C 8574 ic's as in/out expander: 2 chips to read the 12-key 1-octave
> keyboard, interrupt based; 4 bits spare;
> - I2C 8574 ic's as LED outputs: 12 LEDs, one per key, displaying the
> note playing as a sequencer; 4 bits spare;
> - Can easily be expanded to 64 keys in + 64 LEDs out, or 128 things in
> or out, or whatever. (I2C is great!)
>
> - ~16 bit "DAC" without a DAC: using two PWM pins combined, and
> RC-filters, to produce the control voltage;
> - gate signal; gate may be shorter than the note duration for
> "staccato", etc;
>
> - TimerOne interrupt based timing, 120BPM, 24 ppqn, like midi does, if I
> understand that correctly;
>
> - sequence mode: up / down / up-down / random ;
>
> - For each note there's a pitch, a duration and a gate duration,
> internally, although for the arpeggiator note and gate duration are
> currently fixed value (all quarter notes, @ 24 ppqn)
>
> - Operation:
> 1. press START
> 2. press one or more keys of the keyboard
> 3. while you keep the keys pressed the machine loops through the
> corresponding notes
> 4. press STORE to store the melody; you can now release the keys
> ...
> 8289. press STOP
>
> rick
>
>
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