Maybe it depends on the choosen retract speed if you get blobs or not.
I started to think about a new way of extruder ISR timing calculation that should be >20% faster than the current one with enabled LIN_ADVANCE. Instead of calculating the frequency (which consumes “alot” (~17µs) of time), I want choose only between two extruder ISR speeds. One at full speed for normal operation and a slowed down one for hughe pressure adoption moves like they happen on some line junctions due to the jerk setting. During a “pressure adoption move” I want to disable the normal stepper interrupt loop for a few cycles until the extruder is finished, so that the extruder has time to do it’s job and to prevent CPU overload. Up to know it’s experimental, but maybe I will know if it works stable in the next 12 hours…
You could try my new version, see attachment. It should run much faster and prevent blobs and voids. I’m just finishing a test print with nGen, that was never working before due to the needed high K=150. Seems to look good now 
Marlin_20160704.rar (106 KB)
You are awesome!
I will try it for sure… But I’m out of town now til the 19th visiting my sister. I may go into 3D printer withdrawal!!!
Hi Sebastian
maybe a stupid question:
Do you see a chance to adapt your advanced firmware to the Mini?
I would love to dive into it if you say it would make sense.
All the Best
Frank.
Basicaly it will run on at last every direct drive extruder printer. But I don’t want to do a version for the Mini now, because I don’t have one so I can’t help with specific issues. Up to now, I’m not 100% satisfied how the code is running, even with the latest version posted above.
It’s a hard thing to find the balance between even step distribution and not overloading the CPU which is already running on it’s limit with stock Marlin in some situations. I hope to find a solution in the near future!
Finally got an opportunity to try the RC firmware. Thank you for posting it. I like the sharper corners and the smoother top, however…
When I print with the RC firmware, it’s like every layer is shifted one direction or another (both X and Y). I went through and made sure all bolts were appropriately tightened. No help. I reloaded the “official” firmware and the shifting problem goes away (but I see more “flaring” at the corners - boo).
Is there something I’m missing? Some setting I need to adjust?
I’m not very active here at the moment, so sory for the late answer.
You are the first one writing about X/Y layer shift issues with the FW mod, therefore I would expect a mechanical problem (sticky axes) first. I think the stock FW still uses 500mm/s² acceleration for all movements, where my firmware uses 1200mm/s² for travel moves. That might be a source of your problem if your axes already are not that smooth.
So I would suggest trying to move the axis by hand if they move smooth, and if yes check if you still have the problem if you use my firmware with advance disabled (M905 K0).
Sebastian!
Just wanted you to know that I finally tested the new(ish) version. It is working great so far. No blobs! Printing at about 65mm/sec with PLA and K75.
Best,
Joe
Sebastian,
Can you post the IDE files? I need to edit them to add in auto leveling.
Ay chance we can get the source files for the latest version sebastion? The hex does me no good too many customizations…
I love the advance feature. Really works well. It would be great to have on screen menu access to adjust K, as well as a disable for the advance (maybe K=0 accomplishes this?). Don’t know how easy it would be to add that to the parameter adjust menu.
Following so I can try the next build.
That would be great!
1 thing I’ve noticed - everything is better with advance…well almost everything!
Bridging seems not to work as well…I think the variation in pressure over an open space is causing some globs and ‘hiccups.’ Maybe it would be best to add a M905 K0 to the gcode just before the bridging starts…then revert after.
I haven’t tested this exhaustively…but anecdotally it seems to be the case.
J
I am using Taz4 with Lulzbot firmware verion 2014Q3 and plan to upgrade the extruder to Titan with Volcano. Is it possible to use this custom firmware? I am very interested.
Correction - I don’t think bridging is an issue. I think my model had an issue! 
I’ve noticed that in tight circular corners, the extruder sounds like crap. As if it’s performing micro-retractions for every segment of a tiny tiny circle. Anyone else notice this? I’m using the latest firmware as published, no changes to K or other variables.
Yes!
When the extruder has to make a lot of move in a very tight space, I believe the stepper jumps back and forth rapidly to keep up, thus causing a LOT of vibration sometimes.
My guess is that the herringbone gears will wear out faster, and possibly the stepper itself, but I think thats the price to pay for this feature.
The biggest drawback I see is that these intense vibrations are likely being translated to the hotted and therefore the print.
Not sure if it can be fix or not?
J
Yeah, it’s so violent that I’m concerned it’s actually skipping steps during that behavior, causing slight amounts of over/under extrusion afterward. Mostly it just sounds brutal.
I ended up having to go to the third to last version of Sebastian’s firmware (including the most recent one he supplies as a hex only file). The one prior was causing finish issues on certain prints. I didn’t notice it right away. Others had the same problem.
I wish Sebastian would come back and post to the thread again, as I would love to get the newest hex version which resolved those issues. But I can’t use a hex file I have to compile it myself. He’s been gone for quite some time. I hope he is ok and just busy.
As far as the noises go yes it gets loud but I’ve been using this fw for quite some time and haven’t had any issues with anything breaking on the extruder. knock on wood.
Sebastian-
I know you are a busy man!
I love your firmware. I use it all the time.
You’ll probably say no, and I understand - could you compile a version of your latest firmware for the TAZ 6? They changed the fans and heater, and so I understand there are some firmware changes.
Best,
J
For now I’ve switched back to stock firmware, but this advance feature is phenomenally useful. I’ll be waiting to see where it goes from here. If K values become easy to change (maybe like material presets for temperature in stock Lulzbot firmware), and the chattering noise on curves is lessened or otherwise mitigated, it’s an absolute winner. I’m thinking it’s a big part of what’s necessary to bring print speeds to the next level without sacrificing quality.