.. include:: <mmlalias.txt>


Homework: PWM Controller (2026-03-16)
=====================================

Getting
-------

* Update your fork (see :ref:`fh-ss-2024-update-fork`)
* Massage ``googletest`` submodule. This has to be done only once.

  .. code-block:: console
  
     $ git submodule init
     $ git submodule update

Exercise (Test Driven Development - TDD)
----------------------------------------

* New exercise: ``/exercises/pwm/_codebergaccountname_/``

  * **DO NOT MODIFY** anything but ``pwm.{h,cpp}``
  * Test driven development

  .. code-block:: console

     $ pwd
     /home/jfasch/My-Builds/FH-STECE2024-x86_64/exercises/pwm/_codebergaccountname_
     $ ./pwm-suite._codebergaccountname_ 
     Running main() from /home/jfasch/My-Projects/FH-STECE2024/googletest/googletest/src/gtest_main.cc
     [==========] Running 9 tests from 1 test suite.
     [----------] Global test environment set-up.
     [----------] 9 tests from pwm_test
     [ RUN      ] pwm_test.init_ok
     /home/jfasch/My-Projects/FH-STECE2024/exercises/pwm/_codebergaccountname_/test_pwm.cpp:52: Failure
     Value of: ok
       Actual: false
     Expected: true
     
     [  FAILED  ] pwm_test.init_ok (0 ms)
     [ RUN      ] pwm_test.init_nok
     [       OK ] pwm_test.init_nok (0 ms)
     [ RUN      ] pwm_test.set_period_ok
     /home/jfasch/My-Projects/FH-STECE2024/exercises/pwm/_codebergaccountname_/test_pwm.cpp:67: Failure
     Value of: ok
       Actual: false
     Expected: true
     
     [  FAILED  ] pwm_test.set_period_ok (0 ms)
     [ RUN      ] pwm_test.set_period__no_read_permissions_on_file
     /home/jfasch/My-Projects/FH-STECE2024/exercises/pwm/_codebergaccountname_/test_pwm.cpp:88: Failure
     Value of: ok
       Actual: false
     Expected: true
     
     [  FAILED  ] pwm_test.set_period__no_read_permissions_on_file (0 ms)
     [ RUN      ] pwm_test.get_period_ok
     /home/jfasch/My-Projects/FH-STECE2024/exercises/pwm/_codebergaccountname_/test_pwm.cpp:108: Failure
     Value of: ok
       Actual: false
     Expected: true
     
     [  FAILED  ] pwm_test.get_period_ok (0 ms)
     [ RUN      ] pwm_test.set_duty_cycle_ok
     /home/jfasch/My-Projects/FH-STECE2024/exercises/pwm/_codebergaccountname_/test_pwm.cpp:124: Failure
     Value of: ok
       Actual: false
     Expected: true
     
     [  FAILED  ] pwm_test.set_duty_cycle_ok (0 ms)
     [ RUN      ] pwm_test.get_duty_cycle_ok
     /home/jfasch/My-Projects/FH-STECE2024/exercises/pwm/_codebergaccountname_/test_pwm.cpp:137: Failure
     Value of: ok
       Actual: false
     Expected: true
     
     [  FAILED  ] pwm_test.get_duty_cycle_ok (0 ms)
     [ RUN      ] pwm_test.activate_deactivate_ok
     /home/jfasch/My-Projects/FH-STECE2024/exercises/pwm/_codebergaccountname_/test_pwm.cpp:153: Failure
     Value of: ok
       Actual: false
     Expected: true
     
     [  FAILED  ] pwm_test.activate_deactivate_ok (0 ms)
     [ RUN      ] pwm_test.is_active_ok
     /home/jfasch/My-Projects/FH-STECE2024/exercises/pwm/_codebergaccountname_/test_pwm.cpp:172: Failure
     Value of: ok
       Actual: false
     Expected: true
     
     [  FAILED  ] pwm_test.is_active_ok (0 ms)
     [----------] 9 tests from pwm_test (2 ms total)
     
     [----------] Global test environment tear-down
     [==========] 9 tests from 1 test suite ran. (2 ms total)
     [  PASSED  ] 1 test.
     [  FAILED  ] 8 tests, listed below:
     [  FAILED  ] pwm_test.init_ok
     [  FAILED  ] pwm_test.set_period_ok
     [  FAILED  ] pwm_test.set_period__no_read_permissions_on_file
     [  FAILED  ] pwm_test.get_period_ok
     [  FAILED  ] pwm_test.set_duty_cycle_ok
     [  FAILED  ] pwm_test.get_duty_cycle_ok
     [  FAILED  ] pwm_test.activate_deactivate_ok
     [  FAILED  ] pwm_test.is_active_ok
     
      8 FAILED TESTS

* Running single tests and not all at once (handy for occasional
  ``strace`` debugging sessions)

  .. code-block:: console

     $ strace ./pwm-suite.jfasch --gtest_filter=pwm_test.set_period__no_read_permissions_on_file


Additional Information: PWM On Linux
------------------------------------
  
* See how a PWM controller is handled on Linux:
  :ref:`linux_hw_pwm__sysfs`

Additional Information: C++
---------------------------

``bool``
........

* ``bool`` is a dedicated type, don't have to misfit ``int``

``std::string``
...............

.. topic:: See also

   From :doc:`/trainings/material/soup/cxx/cxx03/900-standard-library-miscellanea/string/topic`:

   * :ref:`cxx-string--operators`
   * :ref:`cxx-string--c-compat`
   * :ref:`cxx-string--conversion-to-int`
   * :ref:`cxx-string--conversion-from-int`

* C++ strings
  (:doc:`/trainings/material/soup/cxx/cxx03/900-standard-library-miscellanea/string/topic`)
  are convenient
* Operators (see :ref:`cxx-string--operators`)
* |longrightarrow| Concatentation, assignment (see
  :ref:`cxx-string--conversion-to-int` and
  :ref:`cxx-string--conversion-from-int`)
* Drawback: system calls like :doc:`open
  </trainings/material/soup/linux/sysprog/file-io/open/index>` are
  defined in C |longrightarrow| needs explicit conversion back and
  forth (see :ref:`cxx-string--c-compat`)

``std::filesystem::path``
.........................

.. topic:: See also

   From :doc:`/trainings/material/soup/cxx/cxx11/filesystem/topic`

   * :ref:`cxx-filesystem--concat-compare`

* PWM in ``sysfs`` uses paths heavily
* |longrightarrow| ``std::filesystem::path``
* Conversion to C string: ``path.c_str()``, just like ``std::string``