You should be able to hook to the DB25 directly vs. digging into the control box, but you'll likely need some buffering. The BBB I/O pins are only rated for 3.3V with 3-6 mA drive (depending on the pin), which isn't really enough to directly drive an opto.
The CRAMPS board doesn't really help a lot, since it doesn't buffer the step/dir lines (the small Pololu stepper drivers don't present much load on the step/dir pins). I'd recommend one of two options: * Create your own DB25 cape for the BBB using a prototype cape and a generic buffer like a 74HCT245 or something. There aren't a lot of wires so it shouldn't be much harder than the "flying wire" adapter you made for the Nano. :) * Create a small Pololu sized buffer board that drives the step/dir signals onto the 4-pin stepper motor header. This would let you use the CRAMPS board (or any other board that used the Pololu style drivers). I've thought this would be a good open-source project, and would be useful for *anything* that uses the Pololu style drives (not just BBB based capes) and would allow safely driving larger stepper motor drivers. Good luck! On 6/30/2019 12:38 PM, Doug LaRue wrote: > I have a 3040T 4 axis CNC and currently have grbl on an Arduino Nano > connected to the DB25. > > I was wondering if anyone has tried Machinekit on a CRAMPS board driving > the DB25 directly instead of going inside the control box and replacing > things. The DB25 has opto isolators on the DB25 inputs. > Probably more of a question for Charles unless someone else is familiar > with the drive capabilities of the BBB and input bufffering of CRAMPS. > > They are 4N26 - http://www.vishay.com/docs/83725/4n25.pdf > > DB25P wirings: > From Vide CNC LPT Pinout > db25 Pin Description > 1 A Enable > 2 X Step > 3 X Direction > 4 Y Step > 5 Y Direction > 6 Z Step > 7 Z Direction > 8 A Step ** > 9 A Direction ** > 10 Reset / Abort / E-Stop > 11 Z limit( Mach 3 video =X) > 12 Y limit( Mach 3 video =Y) > 13 X limit( Mach 3 video =Z) > 14 X Enable > 15 Probe > 16 Y Enable( Mach 3 vidoe =Output1) > 17 Z Enable > 18 - 25 Ground > > > > [image: GRBL_Arduino_Nano_DB25_CNC_1.jpg] > -- Charles Steinkuehler char...@steinkuehler.net -- website: http://www.machinekit.io blog: http://blog.machinekit.io github: https://github.com/machinekit --- You received this message because you are subscribed to the Google Groups "Machinekit" group. To unsubscribe from this group and stop receiving emails from it, send an email to machinekit+unsubscr...@googlegroups.com. Visit this group at https://groups.google.com/group/machinekit. To view this discussion on the web visit https://groups.google.com/d/msgid/machinekit/6ad77c5c-c2af-c9e8-e9f9-75b5333ff5bb%40steinkuehler.net. For more options, visit https://groups.google.com/d/optout.
