This is a testing project to enhance the GWN project (GWN, GNU Wireless Network) by coding the core of GWN in C++ (at present it is coded in Python). Please find the GWN Project at https://github.com/vagonbar/gr-gwn/.
The coding in C++ of the core classes in GWN is expected to improve in performance and become closer to the general design of GNU Radio. Since GWN is implemented as an OOT (Out Of Tree) module in GNU Radio, and GNU Radio does not allow inheritance from user blocks, but only from GNU Radio blocks, the implementation in C++ of the core classes of GWN could not follow the straightforward way of inheriting from a GWN basic block, called gwnblock in GWN. This restriction was not found in Python coded blocks, where inheritance from gwnblock did not show any restrictions. Hence, in a new C++ block, all GWN facilities must be included in the new block.
To simplify coding of new blocks, a block creation script was written, which includes all necessary code in a new GWN block by modifying a template to include the new block ports, timers and user parameters. The programmer of the new block is expected to rewrite two functions:
add_init, which stands for additional initialization, where custom variables can be defined, timers can be set, etc.
process_data, where all the actions expected from the new block are coded. This function is invoked when a message is received on a message or timer port, does some processing according to the message received, and optionally outputs another message on any of the available output ports.
An example block called message_timer_example is already created, and can be tested by running its corresponding QA test, qa_message_timer_example.py.
This block receives a message on an input port and outputs the same message on an output port, as well as a message produced by an internal timer, also sent through the output port. In this flowgraph:
`message_strobe --> message_timer_example --> message_debug`
The message_debug block also receives timer messages generated in the block's internal timer.
The creation of a new block similar to the example block described can be done with the following commands:
cd <project_root_directory>/build
../libgwn/gwn_modtool.sh message_timer_repeat 1 1 1
The script gwn_modtool.sh takes the code from a template GWN block available in the ../libgwn directory, and modifies the argument list according to the argumets given to gwn_modtool.sh as positional parameters: block name, number of input ports, number of output ports, and number of timers.
When running the script, the programmer will be asked to enter a user argument list of its own, such as std::string message, float period, int count; this list may be empty.
gwn_modtool.sh is a bash script which uses GNU RAdio gr_modtool to create the new block, which inherits from GNU Radio general gr::block; all the GWN facilities for communicating with other blocks are copied into the new block from the template GWN block. Once created, the programmer will find clearly indicated in the code the functions to rewrite, i.e. add_init and process_data. The new block includes local attributes to capture the user parameters. More specifically, for an argument called arg_name in the user parameters list, the script declares an attribute d_arg_name of the corresponding type, and inserts an assignment d_arg_name(arg_name) in the constructor to capture the argument value (parameter) in the attribute variable.
The following commands create a message_timer_repeat block, as described in the previous section; the user argument list given was std::string message, float period, int count.
cd <project_root_directory>/build
../libgwn/gwn_modtool.sh message_timer_example 1 1 1
(answer questions: argument list, confirm creation, add C++ QA code)
make
make install
python ../python/qa_message_repeat.py
This is for a GNU Radio installation in user space, as described in
https://github.com/gnuradio/pybombs.
For a system wide GNU Radio installation, instead of make install you must write sudo make install.
After creation, if you gave other names to parameters, you must alter the timer initialization in the process_data function. Once done, an output similar to the following is expected:
******* MESSAGE DEBUG PRINT ********
((message . TIMER 1 msg AAAA) (seq_nr . 1) (subtype . timer_0) (type . Timer))
************************************
******* MESSAGE DEBUG PRINT ********
--- A message from message strobe
************************************
******* MESSAGE DEBUG PRINT ********
((message . TIMER 1 msg AAAA) (seq_nr . 2) (subtype . timer_0) (type . Timer))
************************************
******* MESSAGE DEBUG PRINT ********
--- A message from message strobe
************************************
******* MESSAGE DEBUG PRINT ********
((message . TIMER 1 msg AAAA) (seq_nr . 3) (subtype . timer_0) (type . Timer))
************************************
******* MESSAGE DEBUG PRINT ********
--- A message from message strobe
************************************
In the general case, a different number of input and output ports may be given, and proper customization of the add_init and process_data functions is expected.