MESA 6124 and pull-ups on power up or reset

Thanks. I am using only 6124 boards. 1 set up for 48 inputs, and 1 set up for 48 outputs. Leaves a full 24 pins unused at each board, but it seemed cleaner than mixing in IO pins available on the Yurtaev board to barely make the total IO count needed. Yurtaev board setup focuses on the 7 Mitsubishi servos, which is why I got it. May sound anal, but as a noob, I'd really like to get hardware IO testing and boot-up sorted out before jumping into LinuxCNC. I have full ladder documentation for the Meldas 500 control, so I plan to start with Classic Ladder translation of that. My new control console uses 99% of the old IO hardware, but swaps the old monitor and keypad out for and HDMi/USB touch panel and miniature industrial USB keyboard with mouse. Nothing wrong with keeping the existing hardware multi-position switches and discrete LED indicators from my perspective.

I forgot an obvious solution:
reverse the (socketed) pullup resistors

This will make them pulldowns rather than pullups

Interesting. I'm not sure about the internal wiring of the resistor arrays on the 6I24 boards, or how they are connected to the FPGA pins. Makes me a little nervous to assume flipping the resistor array will work if it's not mentioned in the MESA 6I24 documentation. Have you done this, and did it bring all pins low on power up, before the card is configured?

The resistor networks are 10 pins with 9 resistors and pin 1 being the common pin.
if installed in the normal way, pin 1 connects to the pullup voltage (3.3 or 5V)
and pin 10 is GND. if reversed, the resistor network common connects to GND,
making the resistors pulldown.

You would also want to make sure that pre-config pullups are disabled in the FPGA
(W4 down)

Thanks! I had done a quick search on the part # on the resistor arrays and saw it applying to arrays with varying numbers of pins. I wasn't aware of how the sockets were wired on the MESA card.

PCW - Reversing the resistor networks worked slick. All pins on the 6I24 card being used for my GPIO output are now pulldown.

I wonder why MESA doesn't mention this option in their manuals? Maybe it's a concern with customers damaging parts on the board?

Thanks again!