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CY4672 Reference Design Guide, Document # 001-16968 Revision ** 107
8. Power Considerations
8.1 RDK Keyboard
8.1.1 Usage Model
The following usage model are considered for the RDK keyboard.
■ 4 hours per day of 6 keystrokes per second, 5 days per week.
■ 24 hours per day with no activity, 2 days per week.
■ A packet is transmitted on both key-up and key-down events.
■ A ‘keep alive’ is transmitted for each key-down event.
8.1.2 Current Measurements
Per the keyboard usage model, there are 6 keystrokes per second in the active state, and every key-
stroke includes one ‘down key’ packet, one ‘up key’ packet and one ‘keep alive’ packet. The test
mode firmware only sends out one ‘down key’ packet and one ‘up key’ packet for each keystroke.
Therefore, we need to set the typing rate to 8 keystrokes per second in test mode in order to con-
sume the equivalent power of the usage model. It is accomplished by changing the
KEYBOARD_TEST_MODE_PERIOD define in the
config.h file to 50.
In this measurement, the Back Channel Support is not enabled. If it is enabled, the Icc for the active
state will be higher.
The following is the results of PRoC™ LP RDK keyboard current measurement:
Table 8-1. Keyboard Current Measurement
Operation Mode
Icc (mA) with
Supply Voltage =
2.5 V
Icc (mA) with
Supply Voltage =
2.8 V
Average Icc
(mA)
Active mode–Place the keyboard in test mode “the
quick brown fox …” and set the keystroke rate to 8
character per second.
0.96 0.82 0.89
Idle mode–A keyboard is in its normal power on
state and connected to the bridge with no keys
pressed.
0.040 0.040 0.040
Not connected mode–Type the keyboard. 20.3 16.9 18.6
Not connected mode–No typing.
Transition to
idle mode.
Transition to
idle mode.
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