opensteno_qmk/keyboard/hhkb/doc/Power.txt

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HHKB Power consumption
----------------------
**Power consumption
board clock/prescaler keyswitch power ctrl current
--------------------------------------------------------------------------
tmk 16MHz no no 26.4mA
tmk 16MHz pro1 no 45.1mA
tmk 16MHz/2 no no 18.1mA
tmk 16MHz/2 pro1 no 37.3mA
tmk 8MHz no no 18.9mA
tmk 8MHz pro2 no(w/o FET) 32.1mA
tmk 8MHz pro2 no(w FET) 32.1mA withou POWER_ON/FF
tmk 8MHz pro2 no(w FET) 32.6mA with POWR_ON/OFF
tmk 8MHz pro2 15ms(w FET) 21.3mA with POWR_ON/OFF, enumerated but error -32
tmk 8MHz pro2 60ms(w FET) 13.3mA with POWR_ON/OFF, not enumerated
gh60 16MHz 25.8mA
gh60 16MHz USB suspend w LED breathing 17.6-29.1mA
gh60 16MHz USB suspend w/o LED 0.2mA(0.231-0.276mA)
Poker 5.6mA
Poker USB suspend 0.3mA(0.301mA)
gh60 16MHz stock firmware by komar 26.8mA
HHKB pro2 Over All 139.4mA
HHKB pro2 Controller 115.1mA
HHKB pro1 Controller 25.9mA
keyswitch power consumption:
pro1: 45.1-26.4=18.7mA
37.3-18.1=19.2mA
pro2: 32.1-18.9=13.2mA
**Low Freq Crystal or Prescaler?
No advantage of Low Freq Crystal against Prescaled.
Clock routing
X'tal --+---->Prescaler-------> System Clock
|
+---------------------> USB PLL
Design Decision: Install 16MHz crystal on board with using clock rescaler.