Add Function Block

openDAQ™ provides processing features through Function Blocks. They can process Signals either on a Device or on a host PC where the SDK is running.

The SDK is bundled with a few Function Blocks:

Renderer (displays Signal on a desktop window)
Statistics (calculates average and RMS from an input Signal)
Power (calculates DC power from the input voltage and current Signal)

These Function Blocks serve as an example of what is possible to achieve with openDAQ™ SDK. They are not meant to be used in production code.

The following examples use the Statistics Function Block to show how to add a Function Block. Same methods can be used to add other function blocks.

Get a list of available function blocks

The SDK provides a method to get a list of all available types of Function Blocks. This step is optional if the application uses a fixed configuration of modules and the available Function Blocks are predefined.

The result is a dictionary with Function Block id as a key and Function Block type information as a value of the dictionary.

Cpp
Python

// get available function block types
DictPtr<IString, IFunctionBlockType> functionBlockTypes = instance.getAvailableFunctionBlockTypes();
for (const auto& functionBlockType: functionBlockTypes.getKeys())
    std::cout << functionBlockType << std::endl;

function_block_types = instance.available_function_block_types
for function_block_type in function_block_types.keys():
    print(function_block_type)

Add a Function Block

To create and add a Function Block, specify its id in the add Function Block method. If there is no such Function Block available, the method will fail. The result is the Function Block object.

Cpp
Python

// add function block on the host computer
FunctionBlockPtr functionBlock = instance.addFunctionBlock("ref_fb_module_statistics");

function_block = instance.add_function_block("ref_fb_module_statistics")

Get function block type information

It is possible to get additional detailed information about the type of the Function Block:

through Function Block instance,
through dictionary returned by get available function blocks method.

Cpp
Python

FunctionBlockTypePtr functionBlockType = functionBlock.getFunctionBlockType();
std::cout << functionBlockType.getId() << std::endl;
std::cout << functionBlockType.getName() << std::endl;
std::cout << functionBlockType.getDescription() << std::endl;

function_block_type = function_block.function_block_type
print(function_block_type.id)
print(function_block_type.name)
print(function_block_type.description)

Full listing

The following is a fully working example of listing available and adding Function Blocks.

The full example code listing

Cpp
Python

#include <opendaq/opendaq.h>
#include <iostream>

using namespace daq;

// Corresponding document: Antora/modules/howto_guides/pages/howto_add_function_block.adoc
int main()
{
    // Create an openDAQ(TM) instance, loading modules from the current directory
    InstancePtr instance = Instance(MODULE_PATH);

    // add simulated device
    DevicePtr device = instance.addDevice("daqref://device0");

    // get available function block types
    DictPtr<IString, IFunctionBlockType> functionBlockTypes = instance.getAvailableFunctionBlockTypes();
    for (const auto& functionBlockType: functionBlockTypes.getKeys())
        std::cout << functionBlockType << std::endl;

    // if there is no statistics function block available, exit with an error
    if (!functionBlockTypes.hasKey("ref_fb_module_statistics"))
        return 1;

    // add function block on the host computer
    FunctionBlockPtr functionBlock = instance.addFunctionBlock("ref_fb_module_statistics");

    // print function block type info
    FunctionBlockTypePtr functionBlockType = functionBlock.getFunctionBlockType();
    std::cout << functionBlockType.getId() << std::endl;
    std::cout << functionBlockType.getName() << std::endl;
    std::cout << functionBlockType.getDescription() << std::endl;

    return 0;
}

import opendaq

# Create an openDAQ(TM) instance, loading modules from the current directory
instance = opendaq.Instance()

# add simulated device
device = instance.add_device('daqref://device0')

# get available function block types
function_block_types = instance.available_function_block_types
for function_block_type in function_block_types.keys():
    print(function_block_type)

# if there is no statistics function block available, exit with an error
if not "ref_fb_module_statistics" in function_block_types.keys():
    self.assertTrue(False, "Function block not found")

# add function block on the host computer
function_block = instance.add_function_block("ref_fb_module_statistics")

# print function block type info
function_block_type = function_block.function_block_type
print(function_block_type.id)
print(function_block_type.name)
print(function_block_type.description)