LinuxCNC + Mesa 7i92TF: motors barely move and ignore direction changes

Hi everyone,

I’m having an issue with a CNC machine and would really appreciate your advice.

Until now, the machine was working correctly with an old LinuxCNC desktop PC connected directly via DB25. I’m now trying to replace that old PC with a newer mini PC equipped with a Mesa 7i92TF, while keeping the exact same configuration and existing wiring, without making any changes to the machine’s electronics.

The mini PC is connected via Ethernet to the Mesa 7i92TF, which is then connected to the CNC machine through the existing DB25 cable. Communication between the PC and the Mesa seems to be working correctly.

I reconfigured and remapped the axes using PnCConf to make sure each axis was assigned correctly. However, I’m experiencing some strange behavior with the motors:    
When I command an axis to move continuously, it barely moves.    
When I reverse the direction, the axis keeps turning in the same direction, as if the direction signal wasn’t being detected.

My first suspicion is related to the logic levels. The motor controller board is a X214650 and, as far as I understand, it expects 5V signals, whereas the Mesa 7i92TF outputs 3.3V signals. So it’s possible that the 3.3V signals aren’t being reliably detected by the controller board.

Would adding a buffer/level-shifting board, for example one based on a 74HCT245, solve this issue?    
Or do you think there could be a problem with my LinuxCNC configuration, despite remapping the axes with PnCConf?

I should mention that I’m a beginner when it comes to electronics, so please feel free to correct me if my understanding of the 3.3V/5V logic-level issue is wrong.

Thanks in advance for your help!