Section 4. USB Communications
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) |
| |
23
