Matrix Orbital VK204-25 Legacy - Manual (Page 41)

Description In this mode, up to 10 key presses are buffered until the unit is polled by
the host system, via the poll keypad command 254 38. Issuing this
command places the unit in polled mode.
NOTE This command is not available in I 2 C.
Remembered Yes
9.4 Poll Key Press
Syntax Hexadecimal 0xFE 0x26
Decimal 254 38
ASCII 254 “&”
Description This command returns any buffered key presses via the serial interface.
The host system must be set up to receive key codes. When the display
receives this command, it will immediately return any buffered key
presses which may have not been read already. If there is more than one
key press buffered, then the high order bit (MSB) of the returned key
code will be set (1). If this is the only buffered key press, then the MSB
will be cleared (0). If there are no buffered key presses, then the
returned code will be 0x00. Please note that to make use of this
command, the “Auto Transmit Key Presses” mode should be off.
NOTE This command is not available in I 2 C. To read keys in I 2 C mode, one just needs
to address the module and read a byte. No preceding commands are necessary. If there are
no keys pressed the read will result in a 0x00.
Remembered No
9.5 Clear Key Buffer
Syntax Hexadecimal 0xFE 0x45
Decimal 254 69
ASCII 254 “E”
Description This command clears any unread key presses. In a menu application, if
the user presses a key which changes the menu context, any following
key presses may be inaccurate and can be cleared out of the buffer
between menu changes to prevent jumping around the menu tree. It may
also be used, in effect, to reset the keypad in case the host application
resets for whatever reason.
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