This would tally with my experience above.
Check above for a discussion of this issue. 
FYI, I have been working on a new scheduler core that uses custom timer adjustments with CPU cycle count feedback adjustment that does everything on a single timer. It would be millisecond accurate for all DEL, TR.P and METRO, and could guarantee execution priority and predictable timing, even with triggers (the trigger ISR flips a bit and the trigger is processed only when it wouldn’t interrupt the timing of M, DEL, etc).
CV slew update throttling is a current bugbear, insofar as producing predictable results in busy patches.
I had previously shelved the design as I read that timers were adjusted in a subsequent release and thought they might have been good enough for most applications.
If a millisecond-accurate Metro is still desirable, I could try to finish up work on it. It would have to be experimental for some time as it is a significant departure from the current scheduler.
Let me know.
7 Likes
20 characters of 
Edit: I am also signing up for detailed testing with my recently upgraded Rigol scope.
1 Like
Asking here since someone here likely knows the answer:
Where in the H - E - double chopsticks is INIT_SCRIPT set!!! ??? No luck with grepping around at all …
Strangely, it is in turtle.h, accompanied by a comment on the misplacedness of this enum: https://github.com/monome/teletype/blob/38668cacaf64d696023430250339c936df6b2653/src/turtle.h#L43
1 Like
Hah, I was looking right at it but only saw the single line that grep matched–I was looking for a #define!
Adding A, B, and C scripts (and making them callable with $/SCRIPT) was pretty easy once I found that. Thanks so much!!
1 Like
You may have already found this, but while you’re modding firmware it should be straightforward to change the behavior of P.RM and P.POP to do what you want.
1 Like
Thanks! I just spent a few minutes getting USB disk mode to save the new scripts, though reading them back in is proving to be a little fussy.
After that I think I’ll stick to the mainline code for the time being, it’s not that fun to be off in the wilderness when so many smart people are adding cool stuff.
What’s the current status on this @sliderule (or other TT devs) ? I’m starting to want to use TT for more master trigger / clock divider duties, and would like it to thwack tightly.
I would love to try any improved TT firmware, I’m still bitten occasionally, and trying various work-arounds…
If you need really tight timing, I don’t think Teletype’s metro is going to work as a master clock. The inherent jitter isn’t too bad according to some tests: about +/- 1ms. But activity like scrolling around in pattern mode and interacting with the grid sim/preview screen introduces hiccups that will cause havoc with things like clocked delays. I use external clocks: TXo is very stable.
Teletype’s responsiveness to trigger inputs and overall speed is quite good! I’d put it up against a 4ms RCD, which I measured at ~130us latency with about 50us of jitter.
@a773, what kinds of workarounds are you having to use?
My issues are related to i2c triggers being transmitted on later M cycles. I believe this post came just after my post (hence the title), I’m replying here because in my naive book, everything that improves timing might affect/improve/fix my problem…
Haven’t been able to make it work reliably, currently I’m testing clocking $1 from an external source and triggering $2-7 from $1, no conclusion yet. Other workarounds include abandoning completely or partially i2c and resorting to cables (major bummer)…
The problem takes a while (about an hour) to build, making it hard to troubleshoot.
Thx. I have a TXo so will give that a spin.
EDIT : This works a treat! TXo for 4 separate sync’d clocks, with TT as various clock div / mult / etc. utils. Fun times
1 Like
Do you have this code living anywhere online @sliderule? I’ve been thinking about Teletype timing a lot lately, and I’d love to see what you did before I start my own experiments in the area. Maybe I can even attempt to pick the fork up and run with it?
I’m looking for millisecond accuracy with DEL.R, is this scheduler core available now?