For example if I wanted to lookup the purpose of the ‘ratio’ parameter in the LFO module, where would I find this information?
it doesn’t really exist…
I decided to get off my a*se and do something about this, as I have been meaning to create a wiki for this for quite some time…
so here is the start :
https://forum.percussa.com/t/community-documentation-wiki/
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Excellent! I’ll help!
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cool, I think if we get a few involved then we can get the basics in place pretty quickly.
if there are any parameters etc on modules that you don’t know about ,then please feel free to include, and just put a ? beside it,
then, we can then go through and sort out any where there are questions.
similarly, I think if we can get in some basic descriptions, then we can go back later and fill out with more details etc.
I’ll also adopt the same ‘style’ for my modules…
(so need to include parameters/input/output section)
but for now, I just included what Id already documented.
anyway, a little bit at a time for a few users, and I think it’ll be surprising how quickly we build up something very useful.
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@jcgam did you add the LFO documentation - if so - thanks.
its better to not to refer to external images if possible - you can upload images to the SSP.wiki repo directly - Ive mentioned this in the contributing guide (with a link on how to)
I’ll move the image. FYI, I see the same signal if I use a cable directly connected to the scope, or a grounded probe, so the ringdown at voltage changes appears to be in the actual output.
Ive already moved it… as I wasn’t totally sure how it worked 
ring down? the wave shape is because its using bandwidth limiting… this is so it doesn’t alias (as it would if its a mathematical wave)
this was a bit of a surprise to me, as I didnt think they were bandwidth limited… as when I look on the SSP scope and also in my DATA plugin - I didn’t see the edges.
BUT, Ive not realised this is simply the resolution thats being shown on these two scopes… as those edges are only a few samples. -
I did verify on my own scope to check as well, and can clearly see on the output , for both SQ and SW… (others do not need it)
so I learnt something today, so its a good day
btw: I think Ive done all factory modules except GRA, SAM and STE…
but now I need a break from it… spent a lot of time on this today 
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btw: Im not sure what you mean by scale on lfo?
the Pitch Input is v/oct…
the way to view this is…
we have +/- 5v input ,
this translates to -1 to 1 internally
so 0.2 = 1 octave.
viewing it any other way, I believe is very confusing
frequency, is similar but, Id have to check its range and if its linear/exponential
unfortunately there is a bit of a bug (*) on the coarse tuning and the way it works…
a bit complicated to explain, but really you just don’t want to change it if your using Pitch at the moment
(*) basically when you go from a linear scale (like v/oct) to frequency, you do so by going via a base frequency… unfortunately, this is not being done correctly here.
more basically, we can say users should connect pitch->pitch , frequency->frequency, you generally don’t really want both, unless, your doing something like small modulations.
also connecting other things to pitch/frequency needs a bit more ‘thought’ as the scaling might not be what a user thinks… again, unless its small amounts in which case all is good !
we could probably do with a small topic on pitch/frequency in the wiki…
Feel free to change it to something that makes sense. I thought it would be useful to know the correlation between the input voltage and the resulting output frequency.
I guess, but I think most would just see this as v/oct
but we should indeed be mentioning the reference voltage (i.e. 0v = C5 = x hz) , that is important.
see this update
I do, however, think the frequency input and scaling would be useful to know what it is using… since thats something Ive not checked… though Im not sure its that useful from outside the SSP module?!
I’ll also say, Im never quite sure if to talk in voltages internal to the SSP of +/- 1.0…
I know voltages makes sense from a eurorack perspective but we see this +/- 1.0 all over the place.
(unfortunately, this is due to DSP talks -1…1, and physical = volts )
… but again perhaps a quick ‘topic’ on that will show they are equivalent !
If the wave shape was caused by bandwidth limiting we would see relatively uniform oscillations. What we actually see is decreasing oscillations at extreme voltage changes, likely caused by resonant inductive coupling in the circuitry. You see the same signal on your scope?
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ah, sorry yes you are right…
yes, Im seeing the same on my scope (analog discovery 2) , only on square and saws, as you say caused by the extreme edges…
actually this is interesting perhaps I was right before… they are not bandwidth limited then…
would this help reduce this effect?
I passed the output of the DCG module to another output jack and measured the voltage directly.
The only way to eliminate it is a redesign of the output circuitry.
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ok, just checked the square wave is a mathematical wave , no bandwidth limiting.
Id like to compare this to the waveforms from PLTS which are bandwidth limited.
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Interesting, so PLTS also has this ringing… as you say, when we get extreme changes.
PLTS however has an ‘ace up its sleeve’, you can shift the waveform, e.g take a SAW, then you can morph it slightly to a triangle, thus removing then edge… and so the ringing.
interestingly, it takes very little to actually get rid of it…
similarly you can do things like ‘round’ the square wave a bit.
of course, we will only see this on the physical outputs … as a USB audio interface its all transferred digitally… so its then down to what you output it on from there
anyway… back to what I said, learning something today … even if its different from what I thought earlier!
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Zooming in to the top corner of the square wave we see random oscillations that appear to be caused by the analog circuitry: Imgur: The magic of the Internet
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can this resonant inductive coupling also be the reason why bringing any other module (digital or analog) into the same power circuit causes a huge buzz on the outputs ?
I think this is more about the sharp transients inducing ringing…
Ive noticed if you soften the transient even very slightly, it disappears very quickly.
from what Ive seen, the noise is more related to the conditioning on the grounding…
unfortunately, digital modules are prone to putting switch noise on to the ground, the higher W consumption on the MCU/CPU the worst this is.
Ive created physical modules using Bela/BeagleBone Black, and rPI (*) and they have the same issue - you can only really improve it by putting a very large inductor on between voltage source and ground, and trying to pick out the ‘right frequency’ to filter it.
the issue is eurorack does not differentiate between a proper audio ground and general purpose ground, and carry ground over tiny small traces e.g. bus boards/ribbon cables … is an inherent design flaw.
(introduce USB ground loops as well, and it can be a nightmare)
(*) using something more modest like an STM32F4 (which many modules use) and its much more modest, and so easier to manage.