Update docs chapter04_04 even more

examples/chapter04_04/readme.md

@@ -11,10 +11,8 @@ of approximately $\frac{1}{2}~\text{Hz}$.
 
 The class hierarchy consists of an LED base class called
 [`led_base`](https://github.com/ckormanyos/real-time-cpp/blob/master/examples/chapter04_04/src/mcal_led/mcal_led_base.h#L15).
-It is located in namespace `mcal::led`.
-
-Two additional LED classes,
-[`led_port`](https://github.com/ckormanyos/real-time-cpp/blob/master/examples/chapter04_04/src/mcal_led/mcal_led_port.h#L17).
+It is located in namespace `mcal::led`. Two additional LED classes,
+[`led_port`](https://github.com/ckormanyos/real-time-cpp/blob/master/examples/chapter04_04/src/mcal_led/mcal_led_port.h#L17)
 and
 [`led_pwm`](https://github.com/ckormanyos/real-time-cpp/blob/master/examples/chapter04_04/src/mcal_led/mcal_led_pwm.h#L16),
 are derived from the LED base class.
@@ -27,12 +25,6 @@ These include one microcontroller port and three other ports
 located on an external
 serial SPI port expander chip of type MICROCHIP(R) MCP23S17.
 
-The PWM-based LED class controls its LED via dimming
-its associated PWM duty cycle. Toggling is done by
-adjusting the PWM duty cycle back-and-forth,
-switching between $0\\%$ and $100\\%$.
-There is one instantiation of this port class.
-
 The port expander chip is controlled with SPI.
 In this particular example, an all-software bus has been
 developed using four microcontroller port pins toggled
@@ -42,14 +34,19 @@ is derived from a
 base class. It provides a uniform interface
 for rudimentary byte-read and byte-write functions.
 
+The PWM-based LED class controls its LED via dimming
+its associated PWM duty cycle. Toggling is done by
+adjusting the PWM duty cycle, switching
+back-and-forth between $0\\%$ and $100\\%$.
+There is one instantiation of this type of PWM-based LED class.
+
 ## Application Description
 
 The application places five LED base class pointers in an
 `std::array` and subsequently toggles them in a range-based
 `for`-loop in the application task.
-
 The array of LED base class pointers is shown in pseudo-code
-below. It is a singleton-object in the `app_led_base_class_array()`
+below. It is a singleton-object found in the `app_led_base_class_array()`
 subroutine.
 
 ```cpp
@@ -79,7 +76,7 @@ app_led_array_type& app_led_base_class_array()
 The application task performs the toggle functionality
 at a frequency of approximately $\frac{1}{2}~\text{Hz}$ using
 dynamic polymorphism on the elements stored
-in the base class pointer container.
+in the base class pointer container, as shown below.
 
 ```cpp
 void app::led::task_func()
@@ -105,13 +102,13 @@ void app::led::task_func()
 The five discrete LEDs in this example are fitted and setup
 as shown in the following table.
 
-| LED        | Port                        | Details                                                    |
-| ---------- | --------------------------- | ---------------------------------------------------------- |
-| LED0       | microcontroller `portb.5`   | port toggle high / low, $750~\Omega$                       |
-| LED1       | microcontroller `portb.1`   | Timer A, PWM duty cycle $0~{\ldots}~100{\\%}$              |
-| LED2       | port expander pin `GPA0`    | port toggle high / low, SPI software drive, $750~\Omega$   |
-| LED3       | port expander pin `GPA1`    | port toggle high / low, SPI software drive, $750~\Omega$   |
-| LED4       | port expander pin `GPA2`    | port toggle high / low, SPI software drive, $750~\Omega$   |
+| LED        | Port                        | Details                                                  |
+| ---------- | --------------------------- | -------------------------------------------------------- |
+| LED0       | microcontroller `portb.5`   | port toggle high/low, $750~\Omega$                       |
+| LED1       | microcontroller `portb.1`   | `timer a`, PWM duty cycle $0~{\ldots}~100{\\%}$          |
+| LED2       | port expander pin `GPA0`    | port toggle high/low, SPI software drive, $750~\Omega$   |
+| LED3       | port expander pin `GPA1`    | port toggle high/low, SPI software drive, $750~\Omega$   |
+| LED4       | port expander pin `GPA2`    | port toggle high/low, SPI software drive, $750~\Omega$   |
 
 In this example, we use ports from both the microcontroller as well
 as an external port expander chip. Hardware adressing is used

examples/chapter04_04a/readme.md

@@ -2,9 +2,11 @@
 ## LED Objects and Polymorphism via References
 
 Example chapter04_04a implements the same basic functionality
-as does example chapter04_04. Example chapter04_04a, however,
-uses an `std::array` of LED base class references instead
-of base class pointers in order to exercise object oriented polymorphism.
+as does example
+[chapter04_04](https://github.com/ckormanyos/real-time-cpp/tree/master/examples/chapter04_04).
+Example chapter04_04a, however,
+uses an `std::array` of LED base class _references_ instead
+of base class _pointers_ in order to exercise object oriented polymorphism.
 
 ## Application Description
 
@@ -14,7 +16,7 @@ This is because C++ can not store references in STL containers such as
 `std::array`.
 
 The container of wrapped LED base class references is shown in pseudo-code
-below. It is a singleton-object in the `app_led_base_class_array()`
+below. It is a singleton-object found in the `app_led_base_class_array()`
 subroutine.
 
 ```cpp
@@ -42,7 +44,7 @@ app_led_array_type& app_led_base_class_array()
 ```
 
 The elements in the array of LED base class references
-are toggled in the application task each second in the following
+are toggled in the application task once per second in the following
 fashion.
 
 ```cpp