This is a field bus software library with a simple C API for STM32 microcontrollers.
The library supports 2 to 5 bus participants (nodes) per bus segment (1) and up to 250kbit/s bit rate (2) in the basic version. The required microcontroller resources are just 3 GPIO pins, 1 UART and 1 Timer per node.
Should you require higher performance or additional features, please contact us at Bitcontrol GmbH, Switzerland.
No programming related to interrupt processing, response timeouts, packeting, checksum protection, or similar is required. It's all done by this library. Communication results are indicated by return values and error codes.
Just configure what SoC resources it shall use, plug-in its interrupt service routines, start the library and periodically call a handler function that does the work in the background. Then focus on your application development.
Layer 1 is an RS-485 bus, but if only two boards are to be connected, RS-232 or simple 3.3V level UART connections will also work.
For each supported microcontroller family, reference examples are published in this repo.
The major differences to other field buses like CAN, Modbus or ProfiBus are:
- 2 to 5 bus participants per bus segments (1)
- Configurable bit rate from 2kbit/s to 250kbit/s (2)
- Variable message/frame size for efficient throughput
- Operating system independent implementation, works with any OS/RTK or on bare metal
- Supported OSI layers go from layer 1 (physical) up to layer 7 (application)
- The library behaves fully deterministic
- This allows precise simulation of the data flow between the bus participants
- The physical bus length is only limited by the RS-485 specification
- No proprietary hardware required (silicon, connectors, cables)
Notes:
- (1): The technical limit is 31 nodes per segment. In the basic version this number has been limited to 5 nodes.
- (2): The technical limit is around 1Mbit/s on a STM32F401 controller, depending on the system clock frequency, interrupt activities and priorities on the controller. In the basic version this number has been limited to 250kbit/s.
This library doesn't require specific hardware to run on. Although currently only the STM32F40x microcontrollers are supported, the port to different STM controllers is simple. They will be made available as soon as users request them.
Outside the microcontroller, RS-485 bus transceivers are required if the bus system shall utilize an RS-485 bus. However, for initial tests it can also be run on a peer-to-peer RS-232 'network'. If unprotected 3.3V signals suffice, no external hardware is required at all for running this bus system.
There is a Nucleo Expansion Board available from Bitcontrol GmbH, Switzerland. It provides a dual-channel RS-485 bus transceiver chip, plus the connectors necessary to operate the FieldBus19 bus system.
In addition, a dual-channel RS-232 transceiver chip is incorporated on the board. This allows for the setup of a peer-to-peer 'network'.
Write an email to info@bitcontrol.ch if you are interested in a purchase.
However, this board isn't bound to the FieldBus19. It can be used wherever a STM Nucleo board is to be connected to an RS-232 or RS485 network. It thereby provides the necessary line drivers and receivers, and it can be configured via jumpers in various ways.
Its schematics are open source. See the doc/hw folder for details.
Furthermore, starter kits are available.
The smallest contains one STM32F401 Nucleo Board and one Nucleo Expansion Board for the FieldBus19 bus system, plus two loopback cables.
The next larger one contains 2 STM32F401 Nucleo Boards, 2 Nucleo Expansion Boards and several cables for the FieldBus19 bus system.
The largest kit contains 3 boards of each type plus more cables for building a 'real' network.
This is an imcomplete, non-binding list of features, that future versions may contain:
- Fully automatic bus address assignment to participants at bus initialization (no DIL switches or hard-coded addresses necessary anymore)
- Lock mechanism that allows to exclude new, unexpected bus participants
- Hardware fault detection that reports faults to the application and disables the RS-485 drivers permanently if desired
- Communication and fault reporting up to OSI layer 7
For companies who are potentially interested in using this bus system in their products, feel free to use it in your products whereever and as often as you like. There is and will be no claim for fees.
Note however that this library comes without any warranty regarding functionality or reliability, to mention just two of several disclaimers. MPL v2.0 applies.
The following services are available on request:
- Implement additional features
- Ports to STM32 or other microcontroller products not included in this repo
- Remove the restrictions that apply to the basic version
- Safety certification up to SIL2
- Write test applications for specific business domain applications
Please contact us at info@bitcontrol.ch if you wish to discuss possibilities. We're glad to help if we can.
- For more information about this bus system see the folders and files in the doc/ folder.