Waveform starting point when changing patches/engaging effect

Software questions and issues with the FV-1

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zandercircuitry
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Waveform starting point when changing patches/engaging effect

Post by zandercircuitry »

I'll try and keep this rather lengthy story as short a I can... I had originally asked this question over at the SpinCAD forum but Larry said its probably one for this group to tackle.

In short, I'm developing a multi-modulation pedal, with all the patches designed in SpinCAD.

We're trying to implement an external tap tempo switch and LED via a microcontroller, but we are having a few issues figuring out where to start.

Basically we need to know at which point the waveform is at when the effect is engaged or a patch is changed? (ie top, bottom, somewhere specific in the middle)

Im not sure how Larry developed the blocks for the LFOs, and I realise this is a bit of a tall order asking for this, but we're kind of stumped.

The issue isn't so much with the tap tempo switch, its more the LED. If we aren't bang on with knowing where the waveform starts there is a chance the LED will gradually drift over time and cause it to be completely out of sync with the rate of the effect. We tried just listening to it to see it we would tell but didn't figure out anything conclusive.

I assume if I was coding this directly in ASM theres probably an instruction to determine this, but alas... I cannot seem to get my head around writing it.

Any help anyone can offer would be greatly appreciated.

Alternatively, if anyone has any better ideas of how to implement an external tap tempo control it would be great to hear...
frank
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Re: Waveform starting point when changing patches/engaging effect

Post by frank »

In FV-1 the LFOs are continuously running so there is no way to know where the waveform when you engage the effect.
Frank Thomson
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zandercircuitry
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Re: Waveform starting point when changing patches/engaging effect

Post by zandercircuitry »

frank wrote: Mon Aug 19, 2019 8:10 am In FV-1 the LFOs are continuously running so there is no way to know where the waveform when you engage the effect.
Damn, I guess we'll have to try and tackle this from a different angle.

It's definitely achievable as there are several pedals out there with an external tap, just gotta figure out a way to make it work.

The tap itself isn't the issue, its synchronising the LED
Digital Larry
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Re: Waveform starting point when changing patches/engaging effect

Post by Digital Larry »

I'm a little curious - sound s like you want the external micro to run the LED, or is the FV-1 going to run the LED? Because you can connect one of the FV-1's audio outputs to a transistor and couple resistors to drive an LED. Of course you have to scale the voltage properly. Just watch the pin's output current limitations. That way, you send the LFO to the effect at the same time as the LED, there's no chance of it getting out of sync because it's the exact same signal.

If the problem is achieving real sync between an external micro that is doing tap tempo and converting this to a voltage that the FV-1 control input ADC reads, and subsequently converts to a value to use with an LFO, the problem seems more one of calibration at that analog voltage interface.
igorp
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Re: Waveform starting point when changing patches/engaging effect

Post by igorp »

What is about JAM instruction? restart LFO and restart led in MCU
frank
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Re: Waveform starting point when changing patches/engaging effect

Post by frank »

JAM only works with ramps, since the OP said they were doing modulation I assumed they are using the SIN LFOs
Frank Thomson
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igorp
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Re: Waveform starting point when changing patches/engaging effect

Post by igorp »

Hm... It's a good way to get sine LFO off battling LFO''s. only 8 lines and range wider than 20Hz
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