I did read that the communication over Fastbus also happens over the power (mA) and not only over the voltage?
Since it is based on RS-485, exist any libraries to connect an Arduino directly (with a level-converter of course) to the Profibus?
I need to connect the Arduino and the Master galvanically isolated. Can I use opto-couplers for that task? Which are fast enough?
Do you want to communicate over Fastbus or Profibus? They are definitely not the same.
You don't need a level-converter but you need a driver chip fo the RS-485 (p.e. MAX485).Yes you can use opto-couplers, just insert them after the driver chip.As you didn't specify at which speed your profibus communicates (they exist from 9600 to 12000000 baud) it's difficult to give you a suggestion for the type.
Correct me if I'm wrong: but don't I need a library for Profibus? I couldn't find any interface-documentation that states communication-details (eg. impuls-length, bit-adresses and stuff...).
HARTSignal encoding Frequency Shift Keying (FSK) + 0.5 mA via current output signalData transmission rate 1200 baudGalvanic isolation YesPROFIBUS PASignal encoding Manchester Bus Powered (MBP)Data transmission rate 31.25 kBit/s, voltage modeGalvanic isolation Yes (IO modules)PROFIBUS DPSignal encoding RS485Data transmission rate 9.6 kBd, 19.2 kBd, 93.75 kBd, 187.5 kBd, 500 kBd, 1.5 MBdGalvanic isolation Yes (IO modules)
Just out of curiosity: if you can afford to buy such a device, why are the costs of the Profibus chip over your budget?I guess you cannot change the device and take one that has an open communication protocol?