84 lines
2.3 KiB
Markdown
84 lines
2.3 KiB
Markdown
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This folder contains the _picadae_ control code.
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The _picadae_ control program consists of three parts:
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- _tiny_ : Keyboard solenoid driver
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- _ctrl_ : Keyboard central controller
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- _app_ : Monitor and command utility.
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# Architecture
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The keyboard control hardware consists of 8 driver boards
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mounted above the solenoids on the keyboard assembly.
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Each driver board has 11 key driver circuits and can
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therefore control 11 piano keys. Each key driver
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circuit consists of an ATtiny85 microcontroller
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which controls a set of power transistors
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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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The hold state then holds the key down
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during the sustain portion of the note.
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All 88 ATtiny85 microncontrollers are attached
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to a single I2C bus which is shared with
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an Arduino Uno. The application computer
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communicate with the Uno via
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a serial connection. The Uno in turn
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translates messages between the
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ATtiny85 channel computers and the
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application computer.
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# Keyboard central controller : Arduino Uno Serial Interface
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Read a register value of `<count>` bytes from channel `<i2c-addr>`
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'r' <i2c-addr> <register> <count>
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Write a register value of `<count>` bytes from channel `<i2c-addr>`
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'w' <i2c-addr> <register> <count> <value-0> <value-1> ... <value-n>
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# Keyboard solenoid driver : ATtiny85 Firmware
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PWM counter frequency and period.
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for each possible `div` setting
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with 16 Mhz system clock.
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Value | Div | Frequency | Period
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------|------|-------------|-------
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1 | 1 | 16 M | 62.5 n
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2 | 2 | 8 M | 125 n
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3 | 4 | 4 M | 250 n
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4 | 8 | 2 M | 500 n
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5 | 16 | 1 M | 1 u
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6 | 32 | 500 K | 2 u
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7 | 64 | 250 K | 4 u
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8 | 128 | 125 K | 8 u
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9 | 256 | 62500 Hz | 16 u
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10 | 512 | 31250 Hz | 32 u
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11 | 1024 | 15625 Hz | 64 u
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12 | 2048 | 7812.5 Hz | 128 u
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13 | 4096 | 3906.25 Hz | 256 u
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14 | 8192 | 1953.125 Hz | 512 u
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15 |16384 | 976.6625 Hz | 1024 u
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# Monitor and command utility : Python Utility
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