Power Saving
============


MCU+HHKB Power Comsumption
--------------------------
Battery drive:
    idle    18.9mA
    active  35.8mA

USB powered:
    40.0mA


HHKB key switch power control
-----------------------------
MOS FET Nch: BSS138 or IRLML6344T, either works and no apparent difference.
Normally on(pull-up) or off(pull-down)? interms of power saving it prefers pull-down?

Pull-down will be better for power saving, normally off.



Used Timer
----------

8MHz clock
----------
1) 16MHz xtal with system prescaler div2: F_CPU=8MHz, F_USB=16MHz
2) 8MHz xtal with div1: F_CPU=8MHz, F_USB=8MHz
Hardware USART doesn't work at 115200bps with 8MHz(F_CPU).

workaround:
a) use Sotwre serial for communcation with RN-42
b) reduce baud of RN-42 to lower rate;(factory default is 115200bps)
10/03



Slave mode
----------
Discovery/Inquire
Connect/Page

SI,0012
SJ,0012
InqWindw=0100
PagWindw=0100


Sniff mode
----------
0.625ms * <hex>
SW,0320     Very sluggish. Type is not lost but very slow to register.
SW,0160     Still sluggish. may transposed? can type but ...
            Mouse point move intermittently
SW,0020     feel a bit late like stumble(20ms)
SW,0010     feel no latency(10ms)


Deep sleep
----------
SW,8010


TX power
--------
SY,fff4


IO pins
-------
S%,1000         status led and connection control don't work
                GPIO5: status LED
                GPIO6: Connection control
                GPIO2: linked status