Mesa 7i96s P1 basics and MPG

Hi everyone,

This is my first post in this forum, so first of all i want to say that i am really impressed by this community. You have been a great help in my cnc building journey. So Thanks you 

I upgraded my controller setup from an old PC with parallel port interface to a Mesa 7i96s card connected to a newer PC. Now i am working on my pendant/mpg and have modified it to be directly plugged into the P1 expansion port. 

Since i am new to the mesa hardware i want to make sure that my setup does not have a fatal flaw. I basically have two questions

1- my pendant has 6 push buttons and two rotary switches (for axis and jog speed selection). Each button is wired this way, for example Pin 3 and Button 3:

Pin3 (P1) -> button 3 -> ground. 

So the pin gets pulled to ground when the button is pushed (active low). I read it should be done this way since the P1 pins have pullup resistors and are always high when the board is powered up. Is this wiring ok? Do i need extra resistors to limit the current? Many buttons can be pushed at the same time.

2- concerning the mpg/rotary encoder. i have read several posts talking about custom bit files to add encoder "functions" to some pins. Is this step really needed? My former setup had the a and b channels of the encoder connected to normal pins, the signal management was done in the hal. I want to avoid flashing new bitfiles if possible at this stage because i am still not very comportable with this new (to me) hardware.

Thanks !!

I would use 7i96sd_mpgp1.bin firmware as that was designed for this use.
You can use a software MPG encoder but since the inputs are sampled
at the (relatively slow) servo thread rate it will not work very well.

Take a look at this thread:

forum.linuxcnc.org/39-pncconf/51733-7i96...-configurator#295487



 

Thank you for the quick reply. I will try to figure out how to flash the modified firmware.

As for the wiring (first question): do i need any resistors to limit the current or can i pull the pins directly to ground (common)?

You should not need series resistors.
Just make sure that the ground return
of the switches goes only to the 7I96S
ground.