This page contains information for the Graphics Library found inMicrochip Libraries for Applications (MLA). It is not relevant for theMPLAB® Harmony Graphics Library.
Summary
This page describes the configuration and usage of the messaging data structure used in Microchip Graphics Applications. Defined in thegfx-gol.h file and typically named Msg by the application, this structure is used to communicate changes in system input to the graphics processing software. The input sources can be:
- A Touch Screen
- An Input Pin or PIC® Special Function Register (SFR)
- Keypad Device
The Microchip supplied functionTouchGetMsg will populate Msg when using a touch-enabled display offered as part of a Microchip Development tool. For non-Microchip supported touch displays and for all non-touch input detection, the user's application is responsible for identifying input changes and filling in the Msg data structure.
When an input change has been recorded, the application will fill in Msg and pass it to the functionGFX_GOL_ObjectMessage for processing. The sections of this tutorial that coverprocessing user input and thegraphics overview provide the details of how Msg is processed.
Message Structure Definition
Defined in the filegfx-gol.h the structure of the message is:
Msg can be defined in any file with the following code:
Structure for a Touch Enabled Display
When populated byTouchGetMsg for a touch enabled display, Msg will contain:
For Touch Enabled Displays:
Msg.typealways contains value: TYPE_TOUCHSCREEN
Msg.param1 contains the X position of the event
Msg.param2 contains the Y position of the evnet
Msg.uiEvent contains the code for the specific event detected
uiEvent Codes for Touch Displays
| Event Code | Touch Event Detected | |
| EVENT_INVALID | Screen wasuntouched last time and remainsuntouched | |
| EVENT_MOVE | Screen wastouched last time, this time thetouch is in a different location | |
| EVENT_PRESS | Screen wasuntouched last time and istouched this time | |
| EVENT_STILLPRESS | Screen wastouched last time and is stilltouched in the same location | |
| EVENT_RELEASE | Screen wastouched last time, but is nowuntouched |
Once filled, Msg is passed on toGFX_GOL_ObjectMessage for processing.
Structure for Pin or SFR Changes
For non-touch display inputs, Msg is populated with the type set to TYPE_KEYBOARD.
TYPE_KEYBOARD is used when a change in an SFR needs to be reflected on the display. (Note: A change to an input pin will be reflected in the corresponding PORTx SFR.)
Example of an Analog Pin Change
For Analog Pin Changes:
Msg.typealways contains value: TYPE_KEYBOARD
Msg.uiEvent contains EVENT_KEYSCAN or EVENT_CHARCODE
Msg.param1ObjectID of the event recipient
Msg.param2 The new value of the ADC Result register
Expected uiEvent Codes for Analog Pin Changes
| Event Code | Event Detected | |
| EVENT_INVALID | Current ADC value is not significantly different from last reported value | |
| EVENT_KEYSCAN | Current value of the ADC requires the display to be updated | |
| EVENT_CHARCODE | Current value of the ADC requires the display to be updated ( same as EVENT_KEYSCAN) |
Example of a Digital Pin Change
For Digital Pin Changes:
Msg.typealways contains value: TYPE_KEYBOARD
Msg.uiEvent contains valid Event code
Msg.param1ObjectID of the event recipient
Msg.param2 -Not Used-
Expected uiEvent Codes for Digital Pin Changes
| Event Code | Event Detected | |
| EVENT_PRESS | The Pin value is now High and was Low on previous read | |
| EVENT_STILLPRESS | Current and Previous value of the pin is High | |
| EVENT_RELEASE | The input value is now Low and was High on previous read |
Structure for Keyboard Input
For keyboard inputs, Msg is populated with the type set to TYPE_KEYBOARD.
The message structure for keyboards is similar to the structure for changes in digital inputs.
Example of a Keyboard Input
For Analog Pin Changes:
Msg.typealways contains value: TYPE_KEYBOARD
Msg.uiEvent contains EVENT_KEYSCAN or EVENT_CHARCODE
Msg.param1ObjectID of the event recipient
Msg.param2 The value of the input character or scan code
Expected uiEvent Codes for Keyboard
| Event Code | Event Detected | |
| EVENT_KEYSCAN | Value of the Keyscan | |
| EVENT_CHARCODE | ASCII code for the keyboard input |
