5 axis 9 stepper mesa board selection

Mesa 7i96S with 5 steppers and G540 with included 4 steppers should do just fine, although i can not recall how many inputs G540 has? I think it had only 2 outputs.
Mesa 7i85S should add 4 stepper outputs, i think, never used one so not sure.
Mesa 7i84 will add 32 inputs and 16 outputs and wire to Mesa 7i96S through smart serial, leaving the IDC header free for other stuff or G540. There are also 7i70 with 48 inputs, 7i71 and 7i72 with 48 outputs each but one has sinking the other has sourcing outputs.
A bit of warning, not sure what the situation now is with G540, but the old ones had division by 10 inputs, so for precission stuff it was not good, hence i stopped using them. Pitty as they are a capable neat package and i newer understood why they did that, nor got a reasonable answer from them back then.

Picture of the BOB?

That one has buffers on the outputs to drives and optocouplers on the inputs, so should do just fine.
Some other with optocouplers on all outputs and inputs will work only if timings are very loose, slow optos. The max i could get from these was 10KHz and the signal was terrible on the scope.

jimmyrig wrote:

 (anyone use the rs485 port on a mesa 7i96s to control a drive that way?) 

 

I am working on it. I got a Modbus relay board working from a Mesa UART last night. 

The aim is to create something configurable, which is likely to take a while (ie the quick-and-dirty demo above does not indicate that the finished driver is imminent)