Documentation: update USB component documentation (#63)

Documentation/Doxygen/USB/src/ref_files.txt

@@ -20,7 +20,7 @@ Directory                  | Description
 
 <b>Header Files</b>
 
-The API interface of the USB Component is provided in the header file %rl_usb.h.
+The API interface of the USB Component is provided in the header file **%rl_usb.h**.
 The table below provides a complete overview of all public header files.
 
 Header File         | Used by                            | Description

Documentation/Doxygen/USB/src/resource_requirements.md

@@ -17,12 +17,13 @@ on the interrupt nesting and therefore on the priority settings of these ISR.
 | :---------------------------------------------------------------- | :----------------------
 | Stack Size (in Bytes)                                             | + 512 for USB Device Driver
 
-\note
-The stack size requirements depend on the maximum nesting of exception and ISR execution and therefore on the priority settings
-of the various interrupt and exception sources.
+Stack size for the ISRs is typically configured in the application `linker script` or device's `startup_device.s` file.
+The stack size for the ISRs configures only the stack space that is used by exception and interrupt service routines
+of the drivers. The stack size requirements depend on the maximum nesting of exception and ISR execution and therefore
+on the priority settings of the various interrupt and exception sources.
 
-User code that calls API functions of the USB Device Component should have a minimum of 512 Bytes of stack space available.
-Since API functions are frequently called from threads, the thread stack size should be at least 512 Bytes (see below).
+Stack size for threads is configured in the CMSIS-RTOS2 configuration file.
+The stack size of the thread that calls USB Device API functions should be at least 512 bytes large.
 
 ### CMSIS-RTOS2 Requirements {#usbd_rtos_req}
 
@@ -64,7 +65,7 @@ n is the instance number, m is the endpoint number 1...15
 
 The following table shows the memory requirements for read-only (Flash) and read-write (RAM) memory.
 These numbers may be used to estimate the total size requirements of the application, but the actual numbers depend
-on compiler optimizations and target processor and may be therefore slightly different.
+on compiler optimizations and target processor and may therefore slightly differ.
 
 | Component                   | RO Memory [Bytes] | RW Memory (Data) [Bytes]                                                                                 |
 | :-------------------------- | :---------------: | :--------------------------------------------------------------------------------------------------------|
@@ -83,20 +84,21 @@ components used in the application and the configuration of these components.
 
 ### Stack Requirements {#usbh_stack_req}
 
-The USB Host Core receives events sent from the interrupt service routine (ISR) of the USB Host Driver.
+The USB Host Core receives events sent from the interrupt service routine (ISR) of the **USB Host Driver**.
 The stack requirements for the ISR are typically less than 512 Bytes. The total stack space required for ISR depends
 on the interrupt nesting and therefore on the priority settings of these ISR.
 
 | Option (under section Stack Configuration)                        | Increase Value by
 | :---------------------------------------------------------------- | :----------------------
 | Stack Size (in Bytes)                                             | + 512 for USB Host Driver
 
-\note
-The stack size requirements depend on the maximum nesting of exception and ISR execution and therefore on the priority settings
-of the various interrupt and exception sources.
+Stack size for the ISRs is typically configured in the application `linker script` or device's `startup_device.s` file.
+The stack size for the ISRs configures only the stack space that is used by exception and interrupt service routines
+of the drivers. The stack size requirements depend on the maximum nesting of exception and ISR execution and therefore
+on the priority settings of the various interrupt and exception sources.
 
-User code that calls API functions of the USB Host Component should have a minimum of 512 Bytes of stack space available.
-Since API functions are frequently called from threads, the thread stack size should be at least 512 Bytes.
+Stack size for threads is configured in the CMSIS-RTOS2 configuration file.
+The stack size of the thread that calls USB Host API functions should be at least 512 bytes large.
 
 ### CMSIS-RTOS2 Requirements {#usbh_rtos_req}
 
@@ -135,7 +137,7 @@ n is the instance number
 
 The following table shows the memory requirements for read-only (Flash) and read-write (RAM) memory.
 These numbers may be used to estimate the total size requirements of the application, but the actual numbers depend
-on compiler optimizations and target processor and may be therefore slightly different.
+on compiler optimizations and target processor and may therefore slightly differ.
 
 | Component                   | RO Memory [Bytes] | RW Memory (Data) [Bytes]
 | :---------------------------| :---------------: | :-----------------------:

Documentation/Doxygen/USB/src/rl_usb.txt

@@ -72,8 +72,8 @@ be used before any class specific functions are called:
 - Initialize the USB Device Controller, Hardware Driver and a specific USB Device using \ref USBD_Initialize.
 - Connect a specific USB Device to the USB Bus by calling \ref USBD_Connect.
 
-These two functions are accompanied \ref USBD_Disconnect and \ref USBD_Uninitialize. Use them to properly disconnect and
-uninitialize the device from the USB bus.
+These two functions are accompanied by the \ref USBD_Disconnect and \ref USBD_Uninitialize functions. 
+Use them to properly disconnect and uninitialize the device from the USB bus.
 
 Static and Run-Time Configuration
 ---------------------------------

Documentation/Doxygen/USB/src/usb_classes.md

@@ -79,7 +79,6 @@ The documents available at
 [Communications Device Class](https://www.usb.org/documents?search=&category%5B%5D=49&type%5B%5D=55&items_per_page=50)
 describe the nine available request types for the Abstract Control Model (ACM). All requests specified for the Network
 Control Model (NCM) by the documents in ECM120.pdf and NCM10.pdf are supported.
-are not supported.
 
 ### USB Descriptors {#CDC_Descriptors}
 

Documentation/Doxygen/USB/src/usb_concepts.md

@@ -52,7 +52,7 @@ Examples of functions:
 - An imaging device such as a scanner, printer, or camera.
 - A mass storage device such as a CD-ROM drive, floppy drive, or  DVD drive.
 
-The **logical USB network** appears as a star network to the developer with the host at the centre. Hubs do not introduce
+The **logical USB network** appears as a star network to the developer with the host at the center. Hubs do not introduce
 any programming complexity and are transparent as far as the programmer is concerned. An USB device will work the same way
 whether connected directly to a root-hub or whether connected via intermediate hubs. All USB devices are available as
 addressable nodes in this master/slave network. Only the host can initiate a data transfer in the network.
@@ -277,7 +277,7 @@ voice-over-IP phone might have:
 
 Provisions have been made in the USB component to give the user the option to
 \ref Overriding_Descriptors "override the USB descriptors" if necessary. This can be the case when the device class needs
-to be changed at runtime or other reports need to be created.
+to be changed at run-time or other reports need to be created.
 
 ### Device Descriptor {#USB_Device_Descriptor}
 
@@ -522,7 +522,7 @@ configuration that best matches the requirements of the application software.
       - D4...0: Reserved (reset to zero)
      
       A device configuration that uses power from the bus and a local source reports a non-zero value in *bMaxPower* to indicate the
-      amount of bus power required and sets D6. The actual power source at runtime can be determined using the GetStatus(DEVICE)
+      amount of bus power required and sets D6. The actual power source at run-time can be determined using the GetStatus(DEVICE)
       request. If a device configuration supports remote wakeup, D5 is set to 1.</td>
     </tr>
     <tr>

Documentation/Doxygen/USB/src/usb_host.md

@@ -2,7 +2,7 @@
 
 This chapter describes the software structure of the USB Host Component and explains its use for creating an USB Host application.
 
-The USB Host Component simplifies software development of microcontroller systems that allow to connect USB Devices.
+The USB Host Component simplifies software development of microcontroller systems that can communicate with USB Devices.
 
 **Attributes of the USB Host Component:**
 

Documentation/Doxygen/USB/src/usb_migration.md

@@ -17,7 +17,7 @@
 
 - **USB Host specific**:
   - **changed source configuration files to headers** (`USBH_Config_0..3.c` -> `USBH_Config_0..3.h`).
-  - **removed OHCI and EHCI drivers (moved to CMSIS-Driver pack)**.
+  - **removed OHCI and EHCI drivers** (moved to [CMSIS-Driver](https://github.com/ARM-software/CMSIS-Driver) pack).
 
 The following sections show how to migrate projects from previous version of the MDK-Middleware (v7):
 
@@ -102,8 +102,9 @@ can be seen on the right-hand side.
     was selected in the old **USBH_Config_0..3.c** file and copy appropriate controller's previous settings
     to the new configuration file.
   - for **Memory Pool Size** update the new value by **adding 128** since old setting did not include
-    additional necessary space for memory pool internal operation.
+    additional space necessary for memory pool internal operation.
   ![Old USBD_Config_0..3.c to new USBD_Config_0..3.h](usbh_config_migrate.png)
 
 \note **OHCI** and **EHCI** drivers are not a part of the **MDK-Middleware** anymore but are distributed separately
-      via the **CMSIS-Driver** pack, so please consult CMSIS-Driver documentation on how to configure and use those drivers.
+      via the [CMSIS-Driver](https://github.com/ARM-software/CMSIS-Driver) pack, so please consult CMSIS-Driver documentation
+      on how to configure and use those drivers.