Hi Johannes,
Thank you for the reply. If I wanted to run the whole loop faster (by shortening the period during each voice), do you see any reason why it wouldn't work? For example, will the antilog filter setting quickly enough? Will the pitch compensation circuits keep up?
My goal for speeding up would be to increase the immediacy of the "press a key, get a note". At the current loop rate, it could take up 6 ms for that note to come out.
Since I'm now adding a MIDI chain between my keybed and the key assigner, I'm adding even more latency. If I could compensate for the addition of the MIDI latency by pulling latency out somewhere else (by shortening the Polysix's internal loop by a few milliseconds), that would please me.
Thoughts?
Chip
--- In PolySix@yahoogroups.com, Johannes Hausensteiner wrote:
>
> Hi Chip,
>
> 1) Probably it should be "NC" for "no connection". If you look at the
> schematics of the "New Production" you can find this.
>
> Maybe it has a meaning in another keyboard of this era. The same
> key assigner (8049C-217) was used in the MONO/POLY and the first
> generation Poly-61 ("old production").
>
> 2) I think things were not much faster those days. The MCU runs off a
> 6MHz resonator. Due to internal timing this is divided by 15 giving
> a core frequency of 400kHz / 2.5usec. The timer is set to 640usec,
> which matches your measurements (676usec). All the recurring stuff
> (KBD/button scanning, voice CV output, etc.) is done within the
> timer interrupt service routine. Due to different code in different
> phases:
> - slot 0..5 (voices)
> - slot 6..7 (calibrating the antilog amplifier)
> - slot 8 (kbd/button scanning plus other housekeeping)
> slightly different times occur. The timer ISR itself does not take
> that much time but the 4051 muxes are only updated at this rate.
> There is a lot other code outside the timer running - it is pretty
> much stuffed up to the last byte...
>
> Have fun with your project!
>
> Johannes
>
>
> On 2013-02-08 19:06, chipaudette wrote:
> > Hi All,
> >
> > I've started my project to add aftertouch and velocity functions to my Polysix. After studying the schematics and planning out the circuitry needed to implement these functions, I went ahead and ordered the new keybed.
> >
> > To implement the velocity portion, I need to know which Polysix voice goes with each key press. So, I'm pretty sure that I need to replace the built-in key assigner with my own key assigner...this will allow me to have total control over which key press goes with which voice. Since many of the MIDI kits for the polysix already do this, I'm thinking that I'm up to the task.
> >
> > I've started to probe all the signals generated by the Key Assigner microprocessor. I've documented my results on my blog (link below) to show graphs and timing values. I have some questions that you might know...
> >
> > http://synthhacker.blogspot.com/
> >
> > My questions for you all are:
> >
> > 1) What does the "MC" line do? I can't find where it links to anywhere.
> >
> > 2) Why are the voice periods so long (676 usec). If they just wanted to latch in the pitch CV into the S-H circuit, couldn't they have used a much shorter period? If they used a shorter period, wouldn't they be able to greatly increase the update rate?
> >
> > Thanks for your thoughts!
> >
> > Chip
> >
> >
> >
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
>