Power.txt

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.