7i97T stepgen outputs dead, encoders & I/O OK - suspect damaged P2 interface

I’ve been working with a Mesa 7i97Т (Ethernet) board for several months, building a custom machine for forming stainless steel strips (bender).
After long tuning and debugging, the system was finally running perfectly — all axes worked, PID loops were tuned, encoder feedback was stable. Everything was ready for production.However, at the very final stage, a strange and critical issue appeared:
→ All step/dir outputs stopped working.
The configuration hadn’t been changed, firmware is the same, LinuxCNC starts normally, encoder feedbacks are alive, analog channels respond, isolated I/Os work — but there are no pulses on stepgen pins anymore.I’ve checked:

• power rails — OK (5 V stable);
• FPGA communication — OK (hm2_7i97.0.readhmid works, pins visible);
• configuration and HAL wiring — unchanged, verified against backups;
• Ethernet communication — stable (no packet loss).

It really looks like something went wrong inside the P2 connector circuitry.
There is no visible damage, but all signals related to the P2 step generators are either completely absent or there are slight jerks on some axes.The issue happened suddenly, after months of correct work.
That’s why I suspect a hardware failure — possibly in the P2 line driver section of the FPGA or the buffer network.I’ve dedicated months learning, configuring and testing this system — and it’s extremely disappointing that such failure occurred when everything was already finished and tested.
Before I try to order a replacement board (delivery will take weeks), I’d like to understand:

• could this be confirmed as a hardware failure on P2?
• are there any known cases of P2 buffer/transceiver damage on 7i97?
• can I temporarily bypass stepgens via another interface (for example, through TB4 SmartSerial → external 7i85S module)?
• any diagnostic HAL tests to check P2 FPGA I/O status?
  
  I really liked the features of this board, but I am also very disappointed at the moment.

Any insights from Mesa developers or users with similar experience would be greatly appreciated.
Thanks in advance.

1. What daughtercard is used to drive the step/dir outputs?

2. A relatively common cause of parallel expansion failure is voltage exceeding the -0.5 to +7V range applied
to any I/O pin (even for an instant). One easy way to do the is to plug in the P2 connector when the system is
powered and there  is no common ground reference between the 7I97T and the connected device.

3. When damage occurs, the typical damaged component would be U22, this can be checked with mesaflash
assuming W21 is in the up position and P2 unconnected, running:

mesaflash --device 7i97t --addr [card_ip_addr] --rpo 0x1008

Should respond with 0x0001FFFF (all P2 pins read high)

if not, its likely that U22 has been damaged

(U22 is ~$1.50 in ones and relatively easily replaced if you have hot air tools)

Thank you for the detailed explanation and the diagnostic command!
I’ve run the suggested test and got this result:
0001FFFF
As I understand it, that means the P2 outputs are alive and the U22 buffer is fine.
However, the motors still don’t move — there are no step/dir pulses visible on the outputs.
All firmware and HAL configurations are the same as before, when everything was working perfectly.
The P2 connection was made directly through a terminal breakout (type MC-IDC26-H),
and three servo drives were connected in step/dir mode (DB100S type drives).
Could you please advise where else I should look next?
Is there any way to further test the internal stepgens or confirm that the signals are being generated in the FPGA?
Also, which daughtercard would you recommend for connecting three drives via step/dir to the 7i97T - something that would provide a safer or more isolated connection than the raw P2 header?

I know this may sound a little silly but is there a connection between the breakout board's gnd and the 7i97t ground. Some people have either forgotten this or just didn't know.
Not being familiar with your breakout board but does it require a heart beat pulse to enable the outputs ?

Sorry if this sounds a little too basic.

Have you checked the DIR output pins with a voltmeter when jogged in either direction?

A suggested step/dir daughter cards are: 

7I78 (4 differential step/dir outputs 1 encoder, analog spindle interface),
7I85S (4 differential step/dir outputs, 4 encoders, 1 serial port)
7I88 (8 differential step/dir outputs)

common parallel port breakouts:

Sainsmart 5 Axis CNC BOB
CNC4PC C11G
CNC4PC C10

 

I tried connecting a simple stepper motor. There is no rotor movement at all. Most likely, the problem remains in the board itself. Since the board has already worked before and I understand how it should function, the issue is not in the software part. The question is very important for me — is it possible to connect the extension boards you suggested not through the Mesa board’s P2 expansion port, but through its TB4? Because most likely, any extension board connected through the faulty P2 port will produce the same result.

Did you check a DIR pin with a voltmeter? (when jogging both directions)
A voltage reading would be the most helpful for debugging

Another way to check for U22 damage is to measure the voltage
across C111 (on left side of U22) It should be close to 4V
If much lower it indicate that U22 has been damaged.


P2 is the only way to add step/dir outputs to a 7I97/7I97T

 

The voltage is about 4V only on one contact of the three connected axes, on the others it is about 1.2V / 1.6V
What are my chances of restoring functionality by replacing the U22?

Probably about a 90% chance that replacing U22 will fix the issue.

But the issue  likely re-occur if a breakout is not  added and the same drives/wiring are used.

The direct FPGA outputs on P2 are not really designed for field wiring which may have large EMI coupled
from drives, VFDs etc

If it wasn't intended for that purpose, then it should have been written somewhere, and if not, then that's a big minus for the manufacturer's karma! From the instructions:
“This header has a pin-out that matches a standard parallel port.”
And another question: why then does the official firmware 7i97t_5abobd have pins specifically for stepgen?
I am crying out from the bottom of my heart. This is my second machine. The first one was a simple board running Mach3. I wanted to make the new machine better. Meza turned out to be very suitable for this. I even managed to feel it after setting up the external PID loop. Now, in a foreign country and without any income, I am forced to turn down orders because I realize that I cannot guarantee the repair time for my machine.
Please let me know of any real sellers in Europe who sell Meza boards. Maybe this will speed up delivery and save on customs.
Thank You!