Cheap step generator

Hi I have truly terrible latency, tried a few things to sort it out (Disable the PCI GPU, tried to load rtai_smi but get errors.) but the PP BOB is limiting my speed.

I always intended to get a step generator solution I've looked at Mesa 7i73e is there a cheaper linuxcnc solution?

I need same functionality as a PP BOB.
Thanks
Desertboy

I'm not familiar with a 7i73e are you sure you typed the right thing? There is a Mesa card called a 7i73 but it is not a step generation card, it's a smart serial user interface card.

The cheapest options I know of are:
7i90 ($59) - would probably want/need to add some sort of breakout board or Mesa daughter card
7i92 ($89) - could plug in 1 or 2 parallel port breakout boards (like you already have) or a Mesa daughter card(s)
5i25 ($89) - same as the 7i92 but uses a pci port instead of ethernet.
7i96 ($119) - direct connect + could add a parallel port breakout board or a Mesa daughter card.

The 7i96 isn't fully supported in Linuxcnc yet, and you need to jump through some hoops to get the 6 built in isolated outputs to work, but the expansion port can be used for digital io easily (where you would connect a parallel port breakout board) and the step/dir outputs and the 11 isolated inputs all work fine. (There is an experimental branch with full support)

Todd wrote:

I'm not familiar with a 7i73e are you sure you typed the right thing? There is a Mesa card called a 7i73 but it is not a step generation card, it's a smart serial user interface card.

The cheapest options I know of are:
7i90 ($59) - would probably want/need to add some sort of breakout board or Mesa daughter card
7i92 ($89) - could plug in 1 or 2 parallel port breakout boards (like you already have) or a Mesa daughter card(s)
5i25 ($89) - same as the 7i92 but uses a pci port instead of ethernet.
7i96 ($119) - direct connect + could add a parallel port breakout board or a Mesa daughter card.

The 7i96 isn't fully supported in Linuxcnc yet, and you need to jump through some hoops to get the 6 built in isolated outputs to work, but the expansion port can be used for digital io easily (where you would connect a parallel port breakout board) and the step/dir outputs and the 11 isolated inputs all work fine. (There is an experimental branch with full support)

Hi just to confirm if I buy the 5i25 I don't need anything else to get going it will plug into my existing BOB, do I then only need to upload the correct firmware and configure linuxcnc and I'll be up and running with hardware step generation?

I found one in Europe they seem to be uber rare I just bit the bullet and ordered 1 £99 ($140) see how we get screwed in the UK.

A 5I25 or 7I92 (need external BOB) or a 7I96 (built in BOB)
are cheaper than the 7I76E

Not sure about non-Mesa options

Just remember most cheap parallel port breakout boards are not designed to be able to handle the speed potential of hardware step generation. They often have relatively slow optos, not a problem with a slow parallel port, and shouldn't be with an ordinary step motor config (unless your using really high micro stepping and spinning fast). But it can be a problem with high resolution step/dir servos.

I'm using nema 23's with 8x micro stepping, I would like to get ~800-1000rpm is possible.

That actually should be possible with a basic parallel port and a computer with decent latency (<20us), So it should be no sweat for Mesa hardware.

I think the 5i25 is a good choice as to move up to the ethernet options you must run the preemptive real time Linux kernel and your latency will get even worse...

Todd wrote:

That actually should be possible with a basic parallel port and a computer with decent latency (<20us), So it should be no sweat for Mesa hardware.

If I can get that performance I'm happy for now and having a realistic upgrade path is always good, I remember my 486 could be upgraded to a pentium via a daughter board but when I looked into it it cost more than buying a whole new pentium machine lol.