6i25 (5i25) + 7i85s + 7i85s PNCconf problems and questions

Stephanisk wrote:

1. Can I get a stepgen type5 working on the 7i85s? Here come my previous driver into play uln2003... 6motors need to be connected. 4 wires each.

Not using the bitfile that you have, no. The issue is that if you look at the VHD file (or the mesaflash --readhmid output, or the dmesg print) each stepgen only has two pins allocated to it. (step and dir) and stepgen type 5 needs 4 pins.
linuxcnc.org/docs/2.7/html/man/man9/hostmot2.9.html#stepgen
If you look at this VHD file you will see what a multi-pin stepgen loooks like:
github.com/LinuxCNC/hostmot2-firmware/bl.../src/PIN_ST12_72.vhd
(That one uses numbers for the pin functions, corresponding to
github.com/LinuxCNC/linuxcnc/blob/master...hostmot2/pins.c#L126
(The "8" means "Output"))

But: I would suggest not bothering. A ULN2003-based driver can only ever run stepers in unipolar mode, and more critically can not (typically) run in constant-current mode. Much better drivers are available very cheaply.

Can I get microservo motors running on 7i85s? Only 3 wires come out of these motors. +Vcc, ground and signal. (6motors)

The type used on model aircraft? Yes, that can be done with a suitably-scaled PWM signal. It doesn't work especially well with software PWM but the Mesa PWM should be OK.

3. I have 8 step dirs on this 7i85s. And 8 encoders which is great but I would like to have free gpio pins to connect all limit switches seperatly. Is this possible on these cards, can I free up the gpio from the step dir and encoders if not used or are they preset anyhow.

You can free them up. If your loadrt hm2_pci line contains "num_encoders=6" then the input pins for the last 2 encoders become available as GPIO. I think this is only 3 actual IO pins, though, due to the multiplexing.

On the 5i25 side these pins can be set to input or output, but the 7i85 enforces a pin direction just through the hardware.

A simpler approach, and one that will give you a lot more IO would be to attach a smart-serial card to the smart-serial port on one or both 7i85 cards. You can connect any two of these to your existing hardware.
store.mesanet.com/index.php?route=product/category&path=83_88

The 7i85S should be usable. But I can't find any firmware files for the 5i25 that bring the extra stepgen pins out to hardware.
(All stepgens have the pins internally, but the 5i25 / 6i25 firmware chooses whether to connect them to the FPGA IO pins or not).

There is the option of editing a *_34 (34 IO pins indicates a DB25 board) VHD file to make a custom firmware based on the existing firmware.

I have not built firmware for the 5i25, but I have done it for the 5i23. I won't pretend it is a simple process but neither is it impossible.

wiki.linuxcnc.org/cgi-bin/wiki.pl?Editing_MESA_Bitfiles

You will also need the Hostmot2 sourcecode. You can download this from the Mesa website (it is, for some reason, a link under "Specifications" for each FPGA card) or from the LinuxCNC GITHub: github.com/LinuxCNC/hostmot2-firmware
Be aware that the LinuxCNC repository is set up to build bitfiles automatically and uses makefiles. However the Wiki Tutorial is probably the way to go for a one-off special-purpose firmware. The basic firmware source code is the same, however,