I would like to make a Z-World embedded SBC with a Rabbit core behave like a Profibus slave device. It has an RS-485 port, but no Profibus stack, so I would like to program my own from scratch. I don't know if I should shell out approximately $1200 for the complete set of Profibus specs since I don't even know if this job is doable on short notice. Does anyone have any insight into programming a simple subset of the Profibus DP or PA protocol?

-Robert Scott
Real-Time Specialties

 

There is no simple subset of DP or PA, and it isn't really practical to program up the underlying protocol on a microcontroller as the achievable baud rates would be very limiting (Modbus RTU would be a more practical alternative). Profibus generally uses ASICs to implement the transport, and the RS485 interface needs to operate up to 1.5 or 12 meg, which often requires special design (particularly if isolated, or for EMC reasons).

The line of least resistance is to buy an "Anybus" type of card, which generally use a dual port ram interface from the host to Profibus. These are not cheap, but you'll save a good deal of time. Tellima (www.tellima.co.uk) have a range of interfaces which are well regarded, and there are others. If you're doing large volumes, it's very practical to design your own interface, and you can buy a slave stack for the SPC3 (the most widely used ASIC).

Good news is that you probably don't need to read the spec (unless you have an insomnia problem or like reading reams of technical information translated from German). You can learn most of what you need to know via a book produced by the Profibus group (go to the www.profibus.com site to find details) and written by Manfred Popp, called something like "A simple way to Profibus". You'll find the Profibus Trade Organisation very helpful with advice and finding suitable kit.

Cheers

Tim Linnell (Eurotherm)

 

Work is doable in short time period, specially for PROFIBUS slave. We implemented succesfully PROFIBUS slave on Motorola 68302 Microcontroller. Amount of work will depend on your experience with PROFIBUS and hardware. I do not know anything about your hardware but if you know 68302 you will schedule it better.

Anyway it is important to have the standard in order to make proper development.

Good luck!

 

Hi David,

your work on MC68302 is get with a SPC (external profibus controller) or by inside Profibus code?

If you have developed a code for profibus I'm interest too.

Best Regards

Gabriele Corrieri
mailto:[email protected]