[sdiy] triangle hard sync

[David G. Dixon]

Hey Team!

I'm trying to retrofit hard sync onto triangle-core LFOs so I can sync them
with gates, triggers, square waves, etc.  I can get the triangle to reset to
0V with a JFET across the cap, but I also want the triangle to start in the
upward direction every time as well.  I can just about achieve it if I put
sync spikes into the comparator reference voltage input, but the negative
sync spikes cause the triangle to reverse direction, which I don't want.
This wouldn't be a problem if the sync source is a sawtooth, but a square or
a gate signal would always have negative spikes.  I suppose I could add a
rectifier to eliminate the negative spikes, but that seems too complicated.

I see that the Oakley VC-LFO does what I want, albeit in the wrong
direction.

Also, I could probably rig it such that the triangle started at its most
negative point, in which case it would have to go up.  Perhaps I'll look
into that next (that might be better).

In any case, if anyone knows how to do this, or can point me to a document
where I could learn about it, I'd sure appreciate it.  I believe that Magnus
Danielsson had a relevant document, but the link appears to be dead.