5i25/6i25 custom pinout/bitfile/firmware for 3 axis mill with encoders.

Hi, folks!
First of all - have a happy new year!

Last weekends i was happy to pick a brillant shine both Mesa 5i25 and 6i25 cards.
Unfortunately without a breakout cards, so i have a routine to build custom pinfile, bitfile and flash them.
My CNC mill are builded with a well-known chineese cast iron frame:


Axis motors are Nema24 3-phase steppers (1.2 degree/300 steps per round) with 2k encoders and LCDA357h drivers.

Running them hard through LPT port doesn't allow me to make its best and so i choosed to close feedback loop not to a drivers, but to a Mesa card. The main issue was handling error signal while driver was unable to move axis to a position in a given time. Settling time are very small and i want to exclude drivers motion control firmware from process.

So, MESA.

1. I have installed and briefly studied Xilinx Design Tools (ISE Design Suite 14.7).
This link was very helpful to understand the basics:
tom-itx.no-ip.biz:81/~webpage/emc/xilinx...14_install_index.php
So, i opened a project and choose appropriate settings.

2. Supposing me not the one who needs a pinout with three axis STEP/DIR and 3 encoders i have find PIN_7i76_enc_34 pinout.

Comments in the pinfile are wrong, marked with red "?".
3. After cure of some errors and warnings i was able to build bitfile.
4. Since my encoders aren't have index i will change pinout for using differential pairs 1+14, 2+15 and etc. for A|A and B|B encoder lines keeping in mind very fast signal on this pins.
5. STEP signals will be pinned to a lines having dedicated ground wire for lower coupling between AXIS signals.

Please, let me know, am i on the right way?
Am i need to design simple breakout board for external 5V supply and common collector output? Or i can simpy use Mesa 5i25/6i25 5V supply and forget about excess parts?
The goal is to simplify electric part of the machine.

I suggest that you use a breakout board
Wiring the FPGA pin directly to encoders will work
(for single ended encoders) but the input protection
diodes are quite easy to damage with negative
inputs without current limiting.

If you don't want to use a standard breakout,
at least use an external 26LS32 or similar
for interfacing differential encoder signals

Hi, Peter!
Thank you for your fast reply!

PCW wrote:

I suggest that you use a breakout board

Ok, i'll try to design opensourced one.

PCW wrote:

Wiring the FPGA pin directly to encoders will work (for single ended encoders) but the input protection diodes are quite easy to damage with negative inputs without current limiting.

Aren't Pericom PI5C16211 provide some isolation or we really need full ground decoupling?
Will one of ADUM's be good enough based on your experience?

PCW wrote:

If you don't want to use a standard breakout, at least use an external 26LS32 or similar for interfacing differential encoder signals

Yes, this will free some I/O.

I'm thinking about more or less universal breakout board for digital signals where on the one side will be placed components for setting I/O pins as input, while on the another side could be placed components for setting the same I/O pins as outputs. Just solder one side per pin.
So each can easily tune the board for purpose.

The 5C16211/FST16211s provide 5V Input tolerance
and allow the outputs to swing to +5V (with the included pullups)

For differential signals around noisy power electronics
like step motor drives, servo drives, and VFDs, you need a wide
common mode range (this is why a 26LS32 or similar is suggested)

Ah, yes!

I've deeped in topic and now i'm thinking of ADM1485 transeivers with SIP/DIP switches for easy of setting I/O modes or something like 6+6 (8+4) outs/ins presettled and four selectable for ins-outs. No multiplexers, no SerDes, no DACs/ADCs, no additional chips, just simple differential signaling.

There are not so much Mesa breakout boards locally in my country, so this kind of DIY device will provide well enough tuning, good price and easy of straightforward pin assignment. This can be done on the very cheap PCBs inside 100x100 mm cheap chineese manufacturing.
What do you think?