Web Photo Frame Tutorial: Step 8

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Step 8: Review the Application Code

Application File: app.h

Open the app.h file and review the code. This file is generated by the MPLAB® Harmony Configurator (MHC) when you click the Generate Code button. It enumerates the application states and creates a structure to hold application data.

Application States

  • The application states corresponding to the state machine are enumerated as shown in the following image. These states are explained in the next section.
application_states.png

Application Data Structure

  • The global application data structure is defined as shown in this graphic:
application_datastructure.png

Descriptions of important application data structure members:

  • state: Holds the application's current state.
  • slidePauseTime: Keeps track of the pause interval time between the slides.
  • dirHandle: Holds SYS_FS File handle for directory.
  • dirstat: Holds SYS_FS status for directory read.
  • fileHandle: Holds SYS_FS File handle for current image file.
  • fileStatus: Holds SYS_FS File status for current image file.
  • fileSize: Keeps track of the file size.
  • imageResourceHeader: Holds the Resource Header for the slide image (specifies if the resource is image, font, or binary). It also holds type and ID information for the resource.
  • rootNode: Holds the root node of the media (SD card) volume.
  • fileNameTable: Holds a table which has the file names for the volume.
  • fileName: Holds the name of the current file.
  • totalFiles: Holds the total number of files in the volume.
  • imageIndex: Tracks the current image to show.
  • imageReadyToDraw: Tracks if the image is ready to be rendered on the screen.
  • animationStopRequested: Tracks if the user initiated a slide exit.
  • sysTmrHandle: Tracks the delay between slides while the application is in the Slideshow mode.
  • metaDataEnable: Tracks if the metadata of the image is to be displayed.
  • doubleBufferingEnable: Tracks whether to enable double buffering for the Slideshow.
  • currentTouchBehavior: Tracks whether the current touch event is PRESS, MOVE, STILLPRESS, RELEASE, or INVALID.
  • mostRecentTouchX: Holds most recent valid touch position x-coordinate.
  • mostRecentTouchY: Holds most recent valid touch position y-coordinate.
  • imageFrameCount: Tracks the number of frames in an animated GIF image.
  • secondString: Displays the value of pause interval time on the screen.

Application File: app.c

Open the app.c file and review the code. This file is generated by MHC when you click the Generate Code button.

APP_Initialize

  • Allows the application to initialize various tasks and application-related data.

APP_Tasks

  • Implements the application state machine. It is called periodically from the SYS_Tasks function. These states are described in the following section.

1

APP_STATE_INIT:

The application initialization happens in this state. In this state, an event handler (APP_SYSFS_EventHandler) is registered with the FileSystem.

This event handler is invoked if there is a Mount or Unmount of the SD card media.

2

APP_STATE_MEDIA_UNMOUNTED:

State when the media is unmounted. The application remains in this state until a SYS_FS mount event occurs.

3

APP_TCPIP_WAIT_INIT:

State where the application waits for the TCP/IP Stack to be initialized.

4

APP_TCPIP_TRANSACT:

State where the application checks for network changes and displays the new value on the console. In this state, a user LED is toggled, serving as a heartbeat for the TCP/IP activity.

5

APP_STATE_MEDIA_MOUNTED:

State when the media is mounted. The application retrieves the mounted drive for image files.

6

APP_STATE_DRAW_NEXT_SLIDE:

State when the next image's header data is scanned to determine the image format type and set it to the SlideScreen screen.

7

APP_STATE_WAIT_BETWEEN_SLIDE:

The state handles the wait time between slides.

8

APP_STATE_IDLE:

The state the application is in while in main menu, settings, and the feature lists screens. The application also checks for network changes.



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