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Section 4. USB Communications
23
according to a United States keyboard keymap. For example, to transmit the
ASCII character ‘?’ (063 decimal), the character is looked up in a keymap.
For a United States keyboard keymap, the ‘/’ (forward slash) key combined
with the left shift key modifier are stored in the keymap to represent the key
press combination that is used to represent the ASCII character ‘?’ (063
decimal). When the value is set to 1 (ALT ASCII code), instead of using the
keymap, a international keyboard key press combination consisting of the
decimal value of the ASCII character combined with the ALT key modifier is
used. For example, to transmit the ASCII character ‘?’ (063 decimal), keypad
‘0’ is sent combined with left ALT key modifier, next keypad ‘6’ is sent
combined with the left ALT key modifier, last keypad ‘3’ is sent combined
with the left ALT key modifier. In general, if this device only needs to
emulate United States keyboards then this property should be set to 0
(keymap). If this device needs to be able to emulate all country’s keyboards
then this property should be set to 1 (ALT ASCII code). The tradeoffs are as
follows. ALT ASCII code mode is slightly slower than keymap mode
because more key presses need to be transmitted. Some applications are not
compatible with ALT ASCII code mode. This property is stored in non-
volatile EEPROM memory so it will persist when the unit is power cycled.
When this property is changed, the unit must be power cycled to have these
changes take effect. If a value other than the default value is desired, it can be
set by the factory upon request. Examples follow:
Example Set INTERFACE_TYPE property Request (Hex):
Cmd Num Data Len Prp ID Prp Value
01 02 0F 00
Example Set INTERFACE_TYPE property Response (Hex):
Result Code Data Len Data
00 00
Example Get INTERFACE_TYPE property Request (Hex):
Cmd Num Data Len Prp ID
00 01 0F
Example Get INTERFACE_TYPE property Response (Hex):
Result Code Data Len Prp Value
00 01 00
INTERFACE_TYPE PROPERTY
Property ID: 16 (10 hex)
Property Type: Byte
Length: 1 byte
Get Property: Yes
Set Property: Yes
Default Value: 1 (keyboard emulation)