CY4636 WirelessUSB™ LP Keyboard Mouse Reference Design Kit User Guide, Doc. # 001-70355 Rev. *A
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Code Examples
Table 5-26. Example Keep Alive Report (Null Packet Support disabled)
If the bridge does not receive a Keep Alive packet or an up key within a specified interval
(DOWNKEY_TIME_OUT) while a down key is present, the bridge generates an up key to the com-
puter.
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Battery Voltage Level Report
An Application Report Header of 0xFD indicates that this report is a Battery Voltage Level Report.
Table 5-27. Battery Voltage Level Report Format
The Battery Voltage Level ranges from 1 (low) to 10 (full). The Battery Voltage Level Report is sent
after a keystroke that occurs whenever the keyboard has been in idle for more than 8 seconds. The
following table shows an example of a Battery Voltage Level Report with fully charged batteries.
Table 5-28. Table 5.3-18. Example 'full' Battery Voltage Level Report
The following table shows an example of a Battery Voltage Level Report with low batteries.
Table 5-29. Example 'low' Battery Voltage Level Report
5.3.3.7
Ghost Key Detection
Ghost keys are possible on the RDK keyboard because it does not use diodes with the keyboard
switches. Ghost keys are caused when three keys are pressed at the same time and two of the keys
are on the same column and two of the keys are on the same row. When scanning the keyboard, it
appears that four keys have been pressed and it is impossible to tell which three of the four keys are
actually valid. The keyboard code detects this condition and does not send a report until one of the
three keys is released.
For example, assume the keys (RowX, ColumnA), (RowX, ColumnB), and (RowY, ColumnA) are
pressed as shown in
Figure 5-19
. It appears that the key (RowY, ColumnB) has been pressed as
well when it has not since the other keys electrically connect RowY to ColumnB.
Application Report
Application Report Header
0xFC
Byte
Name
2
Application Report Header (0xFD)
3
Battery Voltage Level
Application Report
Application Report Header
Battery Voltage Level
0xFD
0x0A
Application Report
Application Report Header
Battery Voltage Level
0xFD
0x01