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*              PIC specifications for Synchrochord        *
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22.08.2011: First sketch, overview.
07.11.2011: Workout for autotune mechanism.
16.01.2012: Version1.0 firmware for the fingers.

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PIC1: MidiHUB board 18F2525
22.01.2012: Firmware version 1.0

- damper: PWM generation on note off's
                   release force steering (X17-2)
- exciter: velocity steering on note-on's (X17-3)
- velocity/amplitude controll via softshift solenoid pwm
- lights: mapped on notes 120-127
          velo byte steering the flashing speed.
          X11-2    blue LED spotlite on arm
          X11-3    blue LED spotlite on arm

  The velocity byte accompanying a note-on steers the softshift solenoid on the plucker assembly
  The release byte accompanying a note-off steers the force of the damping. If the release value
  is zero (as is the case with most sequencer software) this force will be controlled by the value
  set with controller 33. The damper will always be released from the string after a hold time set by
  controller 34.
- all notes off implemented.  

TO DO: on reception of a tuning request controller (CC22), this board should perform an all notes off.

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PIC2: Pulse/Hold board: fingering control [18F4620]
16.01.2012: Firmware version 1.0
22.01.2012: tested o.k. with the hardware, but we might need individual pulse durations for each solenoid.
- 12 solenoids
-      with aftertouch controll for force modulation (vibrato)
-      On reception of a note-off, the solenoid depressed for the previous note stays depressed. A timer is started
-      and only on run out of this timer, the solenoid will be released. A note-on arriving before expiration of this
       timer will cancel the timer. The duration of this timer can be set with CC30
- Midi Channel: 10
- Note range implemented: 39 - 87
- Controllers:
  CC30  : solenoid release time controller
  CC31  : vibrato speed controller. This will not work on the open string (note 39).
          Periodic pulses (50% duty cycle) using the negative voltage will be applied during note-hold, such that
          the pushing force of the active solenoid will be modulated.
  CC32  : attack pulse duration controller. This controlls the duration of the striking force pulse applied
          to a note-on involving a different solenoid than the one previously depressed.
  CC66  : Power on/off  Has no other function here than releasing all outputs on the board and cancelling all
          active timers.
  CC123 : all notes off. Releases all solenoids and cancels all active timers.

TO DO: on reception of a tuning request controller (CC22), this board should perform an all notes off.

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PIC3: dsPIC  (or 18F4620 steering an intel timer)
- 2 phase generation of sinewaves for the synchronous motor
           frequency = pitch/10, note ON commands
           phase angle between the sine waves must be controllable
- sensor input for actual motor speed ( f= fmot * 8)
- sensor input for actual string frequency [ already handled by PIC4 ]
- second serial input channel for receiving data from tuner controller (?)
- steering of the stroboscope

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PIC4: 18F2525
autotuning mechanism
- tuning motor control: speed * CW/CWW
- pitch sensing input
- e-bow freq. output for tuning excitation
- 3 lights
14.11.2011: First version written gwr, Proton Compiler.
24.11.2011: Tests of hardware and firmware on the prototype board.
23.01.2012: cw and cww output's connected to Weidmueller. Optocoupler-relais tested o.k. with 5V.
24.01.2012: Board mounted on the tuning head assembly.

midi commands to be implemented:
note 120      on/off, velo= flashing speed
note 121      id.
note 122      id.
ctrl. 20      set fundamental tuning (midi note) [same in Hurdy]
ctrl. 22      autotune command
ctrl. 23      excite string using the ebow drive in feedback mode.
ctrl. xx      excite string (plucker)
ctrl. 40      vibrato on/off
ctrl. 41      vibrato speed
ctrl. 42      vibrato depth
ctrl. 66      power up / power down
ctrl. 68      midi output message controller
ctrl. 123     all notes off

midi output messages:
ctrl xx       autotuning ready
pitchbend     gives frequency information in Hz, not standard midi!