CSMIO/IP-M and slave axis functionality

[Jonathan]

You shouldn't just wire two controllers in parallel and drive them from the same BOB output; in theory it might work but I can see that if the driver inputs are opto-isolated, there could be issues. So, ideally, you need a way to generate synchronised drive pulses on master and slave axes. That could be via Mach3 (can it do that internally?) or LinuxCNC (same question),

In LinuxCNC you can just assign two step pins to the same axis and the same for the direction pins. If you are just sending the signal to each, that's a bit of a waste of pins - you might as well connect the same pins to both drivers inputs and if the impedance of the breakout board is too high to drive them properly, just buffer it with your favorite logic gate / transistor. In fact you can kill two birds with one stone here - we need the Arduino board to also be connected to the driver inputs, so the easiest way to do that is to for example put an OR gate in so either signal can reach the drivers. Just be safe I'd block the signal from the parallel port with an AND/NAND gate to ensure the computer can't accidentally move the machine whilst the Arduino is homing it.

Once the Arduino has set the gantry square, you can safely send the same signals to both drivers and leave the Arduino idle, or even use it for some sort of fault protection to monitor both motors and detect loss of synchronization.

It's amazing how cheap Arduino's have become, but I'm starting to like them over a raw PIC just for the ease of programming and deploying them - writing a sketch is very quick in the IDE on the PC then testing it is arguably much easier, IMHO, than doing the same with a PIC

I tend to agree - they're a good 'stepping-stone', until you meet the limits imposed by their IDE, to programming them 'properly' in C/ASM. On a vaguely related topic, have you spotted this one? It's a bit good.

With the an advanced algorithm it homes both motors simultaneously and after that it performs gantry geometry correction.

Advanced, really! The sad thing is that this isn't remotely advanced, so should really be included either way...

It's occurred to me that one could quite easily program LinuxCNC to set the gantry square by making a profile that defines the X axes motors as separate axes. You then run some G-code (or something more sophisticated, who cares) to set the gantry square, then load the normal profile to run the machine.