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5 bar graphs and special characters, 1 command list – Matrix Orbital VK204-25 Legacy User Manual

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4.5.6 Poll keypad (254 38)

This command returns any unbuffered keypresses via the RS-232 interface. The host system must be

set up to receive the key codes. When the display receives this command it will immediately return any

unbuffered keypresses which may have not been read already. If there is more than one keypress buffered,

then the high order bit (MSB) of this returned keycode will be set (1). If this is the only buffered keypress,

then the MSB will be reset (0). If there are no buffered keypresses, then the returned code will be 0x00.

Please note to make use of this command, the "Auto transmit keypress" mode should be off.

4.5.7 Set debounce time (254 85 [time])

[time] is in increments of 6.554 milliseconds.

This command sets the time between key press and key read. All key types with the exception of latched

piezo switches will ’bounce’ for a varying time, depending on their physical characteristics. The default

debounce time for the module is about 52 mS, which is adequate for most membrane keypads.

5 Bar Graphs and Special Characters

The display includes the ability to draw bar graphs (either horizontal or vertical) and allows users to

define up to eight special characters.

Eight characters (ASCII values 0x00 to 0x07) are set aside for use with bar graphs, user defined charac-

ters, and big numbers. Since the same 8 characters are used for each function, the functions may not be used

simultaneously. The characters may be defined or redefined at any time by issuing the commands shown

in this section. Once defined, they may be used either by means of the bar graph commands, or by simply

issuing one of the ASCII values 0x00 to 0x07 (which is not prefixed by the command byte, 254).

5.1 Command List

5.1.1 Initialize wide vertical bar graph (254 118)

This command defines the 8 special / user characters to be blocks suitable for use in drawing wide (5

pixel) vertical bar graphs. Any previously existing definitions will be lost. Once this command has been

issued, any number of vertical bar graphs may be drawn unless the characters are redefined by another

command.

5.1.2 Initialize narrow vertical bar graph (254 115)

This command defines the 8 special / user characters to be blocks suitable for use in drawing narrow (2

pixel) vertical bar graphs. Any previously existing definitions will be lost. Once this command has been

issued, any number of vertical bar graphs may be drawn unless the characters are redefined by another

command

Matrix Orbital

VK204-25

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