Hi

I have a cheap generic Chinese breakout board - like this https://www.ebay.co.uk/itm/333905827471
but it has no documentation and the listing is obscure.

It has a pin marked 0-10V PWM output, which is good - my CNC spindle controller board wants a variable DC voltage to control the spindle speed. However, I'm not at all clear how that variable voltage is produced. I'm using LinuxCNC, and the setting for the parallel port is that pin 16 is PWM output. I presume that LinuxCNC produces a high frequency square wave on pin 16, but I can't get my head round how the BOB knows that pin 16 is the one that controls the voltage on the PWM output. If if does ...