57 lines
1.4 KiB
Markdown
57 lines
1.4 KiB
Markdown
This folder contains the _picadae_ control code.
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The _picadae_ control program consists of three parts:
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- _tiny_ : [ATtiny85 solenoid driver firmware](tiny/README.md)
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- _ctrl_ : [ATmega328 interface unit](ctrl/README.md)
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- _app_ : [Python monitor and command utility](app/README.md)
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# Architecture
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The keyboard control hardware consists of 8 driver boards mounted
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above the solenoids on the keyboard assembly. Each driver board has
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11 key driver circuits which control 11 piano keys. Each key driver
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circuit consists of an ATtiny85 microcontroller which controls a set
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of power transistors which in turn control the state of the solenoid.
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The solenoid can be in one of three states:
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- off
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- attack
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- hold
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The attack state is triggered by pulsing the
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the solenoid with a fast (250 microsecond to
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30 millisecond) 36 volt pulse. The duration
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of the pulse determines the attack dynamic.
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Longer pulses produce louder notes.
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At the end of the attack state the solenoid
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transitions into a hold state. During
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this time the key is held down with just
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enough force to sustain the note.
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All 88 ATtiny85 microncontrollers are attached
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to a single I2C bus which is mastered by an ATmega328 MCU
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which acts as a serial to I2C translator for the host computer.
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The host API is implemented as the Python class 'Picadae' in app/picadae_api.py.
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The control shell program app/picadae_shell.py shows an example
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usage of the API.
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