Modules/Comedi

The translation checking and actualizing

The module provides the OpenSCADA system with the support data sources of realtime, which based on data acquisition boards (DAQ) from different manufacturers, installed on the buses: ISA, PCI, PCMCIA and USB. Drivers implementation for all supported variety boards on Linux kernel side, and also application level library, provided by project Comedi. Full supported boards list, modules to Linux kernel, by project Comedi, also and the module you can get by link: http://comedi.org/hardware.html.

Into Comedi project the unified interface implemented for access to boards data on types data level, that allows, made doing with typical data the boards, not to care further about new hardware supporting on the module side. In current version of the module implemented support for data types: AI (simple poll mode without FIFO), AO, DI, DO, DIO.

The module implements the functions of the horizontal reservation, namely, working in conjunction with the remote station of the same level.

1 Controller object

DAQ—boards by library Comedi into OpenSCADA configured with new controller object creation (Fig.1), the container parameters' objects — DAQ boards.

Fig.1. Configuration tab of a controller object.

From this tab you can set:

• State of the controller object, as follows: status, "Enabled", "Running" and the storage name containing the configuration.
• Identifier, name and description of the controller.
• The state "Enabled" and "Running", in which the controller object must be translated at start up.
• Policy of scheduling and priority of the data acquisition task.

It should be noted that the acquisition data is mainly done in synchronous mode, but for some modules of analog inputs (AI-ADC) that would be optimal asynchronous mode, due to the length of time for value setting after switching a multiplexor channel. For board Advantech PCL-813B the time is 5ms.

2 The controller's parameter object

The parameter object is a direct representative-reflection for DAQ-board, which contained attributes set with types and it quantity depending from specific board. Parameter's object configuration tab is shown in Figure 2.

Fig.2. Configuration tab of a parameter — a DAQ board.

With the parameter's object configuration tab you can set:

• The state of the parameter "Enable" and type.
• Id, name and description of the parameter.
• The state, in which the parameter must be translated at boot: "To enable".
• Address to board's device. Contains the path to the device board. For correct loaded modules to Linux kernel, from Comedi collection, this addresses will allow for select.
• Asynchronous reading. Enable data acquisition into the controller's task cycle, instead reading on demand (Synchronous mode).

Tab "Attributes" for board ACL-8113 is shown in Figure 3. For some types of data can be accessed "Configuration" tab. For example, this tab (Fig.4) for boards with analog inputs has the values set timeout and ranges selection for each channel.

Fig.3. Tab "Attributes" of a parameter of the board "ACL-8113".

Fig.4. Tab "Configuration" of a parameter of the board "ACL-8113".

3 Notes

To build and work of the module only needs library comedilib which is present in most distributions repositories. However, the drivers modules need build separately, and its archive you can download here: http://comedi.org/download.html.

The module work is tested on the following boards:

• Advantech PCL-725, PCL-726
• ADLink ACL-8113