LinuxCNC torque readout and mesa cards

Hi, this is my first post here and my first CNC project. I am trying to build a 5 axis CNC machine with dual-loop feedback position control and for this application I was planning to buy the 7i76E + 2x 7i85 mesa daughter cards but I am not sure if I chose the right cards. I already bought the servo motors with ADTECH QS7 servo drivers which I was going to connect with the 7i85. Is this set up going to work?

Also, I am hoping to get a torque readout on the linuxCNC for every axis but I have no idea how to connect the servo driver to the mesa cards in a way to get the torque reading so I was hoping that somebody could help with some advice. I have seen some videos where people had a torque readout on linuxCNC but I cant find any information on how to wire it with the mesa cards.

Here is an example video of the torque readout on linuxCNC:

Here I attach the link to ADTECH QS7 servo driver manual: www.pcomponentes.com.ar/PDF/AdtechServoDriver.pdf

I would be grateful if anyone could help with good advice. I am just a computer science student and I havent got much experience with CNC machines before. As I said this is my first CNC machine project.

It does not appear that those drives have a way to send torque information back to the host

Its probably possible to use those drives in analog torque mode and thereby control/report the
torque in LinuxCNC but that would require different interface hardware.

Thank you. The drive does have the torque mode. Does that mean I could just use the mesa 7i80DB + 7i77 + 7i74 and run the whole setup analog instead of step&dir and get the torque feedback displayed in linuxCNC with no extra hardware needed?

What would be the drawbacks of using analog instead of step&dir?

Also, is the mesa 7i74 a good choice for interfacing 5 SSI absolute encoders?

Yes, you could use a 7I80DB (or 7I92M) and a 7I77 for this analog interface, _but_ torque mode controls in linuxCNC typically require faster than 1 KHz servo threads and you may run into servo thread speed limitations with your Ethernet host CPU
(some CPUs = can do up to around 4 KHz on Ethernet but they are not common ) Its easier to use a 4 or 6 KHz loop with a PCI or PCIE card

A 7I74 is a good SSI interface card (and there are standard pinout files for a SSI config on a 7I74)

Thank you for all the help. So, I assume that even if I went with a very good CPU and PCIE connection I would still get better, more precise results using the velocity mode or position mode on the drive as I could get much higher frequencies on the drive loop, is that correct?

Could I just use some external torque meters and connect them in a similar way to the external encoders or would that be too complicated? The only reason I want to have the torque readout is to know whether I can push the machine harder and run the job at faster speed.

If I wouldn't be able to use external torque meters in the step&dir setup then what CPU would you recommend to use in the analog setup to ensure no servo thread speed limitations and latency problems?

So, the drive manufacturer told me that the drives can send the motor current status and the motor load ratio to the PC over the ModBus protocol which would let me get the torque readout. How can I use the ModBus with 7i76e and LinuxCNC?

Also, I bought the 7i74 for the SSI encoders. Where can I find the pinout files for the SSI config on 7i76e and 7i74 set? I got the 7i76e working fine controlling the servo drives but I'm not sure how to use the 7i74 with the 7i76e as it doesn't show up in the PncConfig.

I attach a link to the servo drive ModBus protocol manual:
pdf.directindustry.com/pdf/adtech-shenzh...n/114531-657678.html

Have a read of this thread. It might work for you

forum.linuxcnc.org/27-driver-boards/3328...th-uart?limitstart=0

At the moment I just use the default bit-file that came pre-installed on the card. This is actually the first time I use Mesa cards so I wouldn't know too much about how to program them.