Does anyone know the voltage situation regarding multi-drop nodes on an RS485 bus please?
Nick Gammons RS485 article shows 2 different hardware configurations, one using 5v devices, and another using 3.3v devices, and I am fairly sure my Pelco PTZ CCTV system uses 12v.
But I have never seen anything mentioned anywhere about needing to voltage-match nodes on an RS485 bus.
So I am unsure whether the MAX driver chips isolate the RS485 bus voltage from the mcu logic levels.
Or do any lower voltage devices (3.3v or 5v) need logic-level matching to their MAX driver chips, which all need powering from the higher bus level (perhaps 12v)?
Basically, I wish to add an 'intelligent' arduino controller to an existing ptz cctv system.