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Create new Wrapper Library

The following steps have to be taken in order to create a custom wrapper library. See also flink-eeros or comedi-eeros.

  1. Create new CMake project for a shared library.
  2. Include and link against EEROS:
    find_package(EEROS REQUIRED)
  3. Include and link against necessary hardware library. If the required hardware library generates a CMake Package, use find_package() to search for the library:
    find_package(flink REQUIRED)

    If you have no CMake Package you have to search for an installed header file or add it as additional include and library directory.

    find_path(COMEDI_INCLUDE_DIR NAMES comedi.h comedilib.h)
    find_library(COMEDI_LIBRARY comedi)
    	message(STATUS "-> libcomedi available")
  4. Create classes for every type you intend to support (AnalogOut, DigitalIn, PWM, …):
    1. These classes have to derive from the EEROS HAL classes In- or Output respectively ScalableIn- or ScalableOutput. You can find these classes in the EEROS repository in folder /includes/eeros/hal. This allows you to access the member functions of the derived classes when they are loaded dynamically over the configuration file.
    2. Implement the derived functions for every class. The set() and get() functions have to access the hardware library and write or read from hardware according to their functionality.
    3. For scalable channels scale and offset (member variables of ScalableIn- and ScalableOutput) have to be taken into account. Calculate the effective output value set to the hardware with these values. Check AnalogOut of comedi-eeros for an example. Scale and offset describe the scaling factors of the connected hardware. So you have to divide the output value by scale.
    4. Create a C function createType, which will be called dynamically from EEROS for every supported type. This function has to create an object of the corresponding type and returns a pointer to it.
    5. Create all necessary Feature Functions as C functions. These are intended to use for all actions which cannot be called with the derived functions like setting a PWM frequency.
  5. Create a class to handle the hardware device node (open, close, …). Create a factory for the device. On every creation of a channel there will be an access to getDevice() and you have to make sure that the device is opened only once.
for_developers/wrapper_lib.txt · Last modified: 2017/04/18 12:43 by kalberer