FAQ
FAQ
What is PBMaster?
PBMaster is a software implementation of the Profibus standard. The framework is based on common cheap hardware and open-source software. PBMaster runs on PCs and embedded systems, where UART with RS-485 output is available.
What is Profibus?
Profibus (Process Field Bus) is the most popular type of fieldbus with more than 28 million devices installed worldwide by the end of 2008. Profibus was developed in 1989 as the result of a German research project involving 15 firms and research institution. In Europe Profibus dominates with more than 60 % of the factory automation market.
Profibus-DP (Decentrallised Periphery) is the most used variant of the standard Profibus. This variant is used for fast remote inputs and outputs, to connect sensors and actuators to a controlling device. For more information please visit http://www.profibus.com and wikipedia.org
The following picture shows the integration of PBMaster in the Profibus network.
What is the goal of PBMaster?
Currently, most of the Profibus solutions are based on hardware specifically designed for Profibus use. The software of these solutions is mostly proprietary, which make them expensive for many applications. PBMaster is a software implementation of Profibus. The objective is to spread the use of the standard also in low-cost applications by using common hardware and open-source software.
A big advantage of the software implementation is that it could run in a wide range of hardware, where UART circuit with RS-485 output is available. It is possible to use the software implementation in applications, where using the current solutions with hardware support (ASICs) would be inconvenient.
Why PBMaster has been set up?
PBMaster started as my bachelor work and later as my diploma thesis (graduate work).
What license is PBMaster released under?
PBMaster is released under GNU General Public License. This means the program is free software. You can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 2, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY. Without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License and the LICENSE file included in the source codes for more details.
Relationship between PBMaster and ProfiM?
ProfiM is a project implementing Profibus Master by software written for Windows. Inspite of this existing implementation, the PBMaster project has been written from the scratch due to the instability and bad performance of ProfiM's implementation. PBMaster was designed to be fast and modular, which make it portable and multiplatform.
What are the supported hardware?
There are several options to connect to the Profibus network. It is possible to run the software implementation on a big range of hardware, where the UART circuit with RS-485 is available. The drivers run on PCs as well as embedded boards with microcontroller. Please consult the List of supported hardware for more information.
The highest attainable speed?
The highest attainable speed depends on the UART circuit, on the bus transceiver, on the capacitors of the input/output circuits and the CPU/MCU. Please consult the List of supported hardware for more information.
What about the performance?
What is RS-485?
EIA-485 (formerly RS-485 or RS485) is an OSI Model physical layer electrical specification of a two-wire, half-duplex, multipoint serial connection. The standard specifies a differential form of signalling. The difference between the wires voltages is what conveys the data. One polarity of voltage indicates a logic 1 level, the reverse polarity indicates logic 0.
EIA-485 only specifies electrical characteristics of the driver and the receiver. It does not specify or recommend any data protocol. EIA-485 enables the configuration of inexpensive local networks and multidrop communications links. It offers high data transmission speeds (35 Mbit/s up to 10 m and 100 kbit/s at 1200 m). Since it uses a differential balanced line over twisted pair (like EIA-422), it can span relatively large distances (up to 4000 feet or just over 1200 metres). The standard is used highly in industrial environment.
