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CSS is using spindle.speed-in to do something, correct? What does the control loop look like for that? Does it influence the speed-out based on the speed-in feedback or something with the feed based on speed-in?

Geesh the first thing I remeber using a parallel port for was tone generation using a R2R digital to analogue converter (well a buffer connected to 2R2 network), almost a very frequency function generator.
Then using it to power some a steppers via a H-Bridge for a silly little robot platorm. Then some 433MHz remote control, a "sledge hammer" logic analyser knocked up a breadboard, a DCC model train control station, first running under DOS, then wrote a vxd in assembly for win95 to replace the DOS TSR. Probably some other stupid stuff as well.

Never got to play with thing like zip drives, ethernet or sound with the parallel port, used to get most of my stuff 2nd hand at computer markets, this was before ebay took off. Kind of miss wondering around the markets and seeing what exotic stuff you could get.
AT one time I actually used it for connecting to a printer, had to get rid of my HP Laser Jet just last year, to be honest I found it on the side of the road and got a good 10 years of service out of it, made quite a few PCBs using the toner transfer method. That doesn't make sense nowadays when you can get 5 double sided PCB shipped down under for about $7 AUD, just a bit of a wait that's all.

Ahhh that's right I used laplink as well for transferring files. MSODS 6.22 had Intersvr & Interlnk for file transfer aswell.

post your gcode file, i can test it out this week. I havent tested out CSS yet, and ive been trying to figure out how it works. because with threading it runs fine, but with CSS i think it is using the spindle speed-in pin.

If spindle0.speed-in has control on the rpm signal based on the feedback it receives, that would make more sense of your issue.
You removed the lowpass filter gain from the hal file. Im not sure what it defaults to. 0.001 was the gain that worked for me without jumping around, but it took longer to stabilize at speed
Monitor this pin on the halshow, spindle.0.speed-in when trying to css, and see what it looks like.

Your spindle PID in the ini file arent hooked up to anything, so they wont do anything.

RE: spindle gain, sorry about that murphy, I got confused between some configs and got some decimals mixed up. The correct way is 100/maxrpm.

Also when I set the gain to 0.0025 which should be the correct value for 4000rpm. It doesn't scale right. I need to input 0.02 for it to work.

if it works, whatever, but maybe look into it. with gain at .02 that would make 4000rpm 8volts.

Pretty sure 2.7.4 will not work with Mesa 7i96, but it will work with Mesa 5i25 and some others, not important, use 2.7.4 with parallel port and for Mesa 2.8.4 or 2.9.4 or Master.

Thanks for the heads up re: that thread. I'll take a look. And good to know that the RPi5 is so fast. Haven't had a chance to try one yet. Maybe someday. But yes, if my RPi 4 doesn't work out, definitely I'll switch back to a PC. (I don't have high hopes for the RPi.

My current PC still works (in fact, running Wheezy with 2.7.4, from ram off of a thumb drive), but it gives nasty warnings if I try and install something new, and it's old enough that I'd rather replace it on my schedule than wait for it to fail. And with the 7i96, I'll get to clean up some really messy wiring that's waiting to fail, as well. So I'm kind of looking forward to the change.

My "obsession" with parallel port is not a result of using it for CNC machines, oh no, it started in the PC/XT and PC/AT era when i used it for transferring files between PC's, and using floppies was considered "mild torture", had some DOS software named "fx.exe", boot from floppy, run it and choose the send/recieve PC and it moved.
Never failed, ever, and was much, much faster than floppy or serial or InfraRed.
Unfortunately, i can not find it anymore, i did have a need for it last year when i fixed all my old laptops, as one of those has a really old and thick HDD that can not be powered through USB-IDE adapters. Had to use IR...got some more gray hairs!
LinuxCNC (EMC2 back then) only reinforced that obsession.

Would the 2.7.x version support a 7i96 ?

RPi4 will be cool (as much as learned colleague Tommy isn't a fan ), but I would do this slight mod to the image, sorry I missed this when creating it, any other issues blame me. One user had an issue with GMOCCAPY locking up after a period of idleness.
If it was a choice between buying an RPi (5 would be the best choice out of the lot) I'd recommend as SFF pc, better bang for buck.
forum.linuxcnc.org/9-installing-linuxcnc...only?start=30#322251

If it was a choice between buying an RPi (5 would be the best choice out of the lot, blazingly fast with an NVME drive) I'd recommend a 64 bit PC platform, 3rd gen I5 is fine, as they are better bang for buck compared to a RPi.

Actually the whole thread is a jolly good read and tries to answer a lot. If you have an other questions be sure to add to the thread.

Does Mesa ethernet work with the RTAI kernel or just RT_PREEMPT ?

tommylight wrote:

F@king google, can not find the chip that was used as parallel port on mainboards, it was something like 665 and some other numbers...or 8255 i think, been to long, and google isn't helping at all.
 

Early versions used discrete components (think XT 74LS374 according to the tomb linked below), usually these were ISA cards, 8255 sounds about right maybe some more dedicated chips later then the Super IO chips, which actually connect via LPC bus.
en.wikipedia.org/wiki/Super_I/O.

For those interested in ancient history
ia800901.us.archive.org/26/items/f15_Par...images_processed.pdf

You can still use 32Bit PC's, there are older LinuxCNC ISO's still available for download so give it a try
I think this is the latest 32Bit version
www.linuxcnc.org/iso/linuxcnc-2.7.14-wheezy.iso
And if it is even older, here are the some more to try
www.linuxcnc.org/iso/ubuntu-10.04-linuxcnc3-i386.iso
www.linuxcnc.org/iso/ubuntu-8.04-desktop-emc2-aj13-i386.iso
They all work from USB without installing them, so you can actually run machines from the USB, granted the PC can boot from USB, and most can, from ~2000

What if you try 0xD010 ?

I think a parallel port card is basically 3 latched, buffered, 8-bit shift registers attached to a very primitive MCU.

2 bidirectional shift registers.
1 Parallel in, serial out shift register.

And a CMOS not gate on 4 pins.

Seriously dude your techno babble never ceases to amaze me.
MCS9900 Diagram 


Can't link directly to datasheets but you can find it on this page.
asix.com.tw/en/product/Interface/PCIe_bridge/MCS9900

Interesting idea:

Connect one of the pins on your breakout board to a falling-edge-triggered shift register to turn one output into 8 outputs!
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Already an example of that on the wiki. Bit more involved than what you suggest.
wiki.linuxcnc.org/cgi-bin/wiki.pl?Shift_Register_Port_Expander

 

F@king google, can not find the chip that was used as parallel port on mainboards, it was something like 665 and some other numbers...or 8255 i think, been to long, and google isn't helping at all.

PCW gave a very valid solution, so that has been covered.
The driver in use covers both functions of the board, and if you look at the dependencies of the driver you'll see that the parallel part uses parallel port modules.
But that is neither here nor there, the thing is a solution has given and if you really really want a change you'll have to mention on GitHub , as that's where the changes happen. You can go on and on posting messages on the forum but it'll do SFA.
And in reality it is only a minor thing that doesn't affect the functionality. If you get no response from the Devs there's nothing to stop you from cloning the repo, editting the source file and rebuilding from source, the build procedure is very well documented in the docs. I linked to the file where the message comes from, PCW gave a solution, all the hardwork has been done. Now the ball is in your court, if you choose not to do anything,nothing will change, if you choose to get involved and not just complain something may happen.
Or you could attempt to completely rewrite the detection routine.
This is how open source projects move forward. The forums are just really for user support, code stuff usually gets done via the Devs mailing list or via GitHub. Links to these resources can be found on the Linuxcnc home page.

The IRQ32 plate is the one that triggers the ALRMA

That's all excellent to hear. I pulled the trigger and ordered one this afternoon, after I realized that my mill PC was not only out of date by years, but also not upgradeable, since it's a 32-bit machine. I have a spare RPi 4 that I'll try with the 7i96. If I'm not happy with that (unlikely), I'll pick up a used small form-factor PC.

paul