Profibus slave device programming?

- R
- Robert Scott
  
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posted
20 years ago

Sat, Oct 18, 2003 7:05 PM

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

-Robert Scott Ypsilanti, Michigan (Reply through newsgroups, not by direct e-mail, as automatic reply address is fake.)

- S
- Stef
  
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posted
20 years ago

Sat, Oct 18, 2003 11:16 PM

IIRC the older profibus runs at 1Mbps and the newer at 12Mbps and I don't think it uses the standard uart protocol.

Our first profibus-dp product used a cots profibus rs232 board, requiring only software for the 232 side to communicate with our device. When we started a project to implement profibus-dp onboard, we decided to use the SPC3 asic, which handles the lower level parts of the protocol.

Sadly this project was canceled before it was completed. But I do remember it required a fair amount of software even though we used the SPC3. And had we completed it, we would still have needed to go through the cerification process before being allowed to sell it as a profibus-dp product.

I'm not sure if we had the complete spec. All this was over 5 years ago, so things could be different now.

--
stef

- P
- Paul Keinanen
  
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posted
20 years ago

Sun, Oct 19, 2003 9:10 AM

Profibus-PA is not compatible with ordinary UARTs, but Profibus DP is standard asynchronous characters over RS-485, so I do not see why a standard UART would network. Older Profibus-DP devices operated at various speeds up to 1.5 Mbit/s, while newer also support 3, 6 and 12 Mbit/s.

The problem in software implementations is the requires response time from the poll, so at least the higher speeds are out of the question. I haven't seen any certified software implementations, but at least some Profibus analyzers seems to be available, that are implemented in software.

Paul