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@@ -199,24 +199,48 @@ static inline bool read_bit(void)
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{
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// ADB Bit Cells
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//
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- // bit0: ______~~~
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- // 65 :35us
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+ // bit cell time: 70-130us
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+ // low part of bit0: 60-70% of bit cell
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+ // low part of bit1: 30-40% of bit cell
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//
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- // bit1: ___~~~~~~
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- // 35 :65us
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+ // bit cell time 70us 130us
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+ // --------------------------------------------
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+ // low part of bit0 42-49 78-91
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+ // high part of bit0 21-28 39-52
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+ // low part of bit1 21-28 39-52
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+ // high part of bit1 42-49 78-91
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//
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- // bit0 low time: 60-70% of bit cell(42-91us)
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- // bit1 low time: 30-40% of bit cell(21-52us)
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- // bit cell time: 70-130us
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- // [from Apple IIgs Hardware Reference Second Edition]
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//
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- // After 55us if data line is low/high then bit is 0/1.
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- // Too simple to rely on?
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+ // bit0:
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+ // 70us bit cell:
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+ // ____________~~~~~~
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+ // 42-49 21-28
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+ //
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+ // 130us bit cell:
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+ // ____________~~~~~~
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+ // 78-91 39-52
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+ //
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+ // bit1:
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+ // 70us bit cell:
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+ // ______~~~~~~~~~~~~
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+ // 21-28 42-49
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+ //
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+ // 130us bit cell:
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+ // ______~~~~~~~~~~~~
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+ // 39-52 78-91
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+ //
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+ // read:
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+ // ________|~~~~~~~~~
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+ // 55us
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+ // Read data line after 55us. If data line is low/high then bit is 0/1.
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+ // This method might not work at <90us bit cell time.
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+ //
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+ // [from Apple IIgs Hardware Reference Second Edition]
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bool bit;
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- wait_data_lo(75); // wait the beginning of bit cell
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+ wait_data_lo(75); // wait the start of bit cell at least 130ms(55+0+75)
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_delay_us(55);
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bit = data_in();
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- wait_data_hi(36); // wait high part of bit cell
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+ wait_data_hi(36); // wait high part of bit cell at least 91ms(55+36)
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return bit;
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}
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@@ -258,7 +282,7 @@ Resources
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---------
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ADB - The Untold Story: Space Aliens Ate My Mouse
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http://developer.apple.com/legacy/mac/library/#technotes/hw/hw_01.html
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-Apple IIgs Hardware Reference Second Edition [p80(Chapter6 p121)]
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+Apple IIgs Hardware Reference Second Edition [Chapter6 p121]
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ftp://ftp.apple.asimov.net/pub/apple_II/documentation/Apple%20IIgs%20Hardware%20Reference.pdf
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ADB Keycode
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http://72.0.193.250/Documentation/macppc/adbkeycodes/
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@@ -376,9 +400,9 @@ Communication
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Global reset:
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Host asserts low in 2.8-5.2ms. All devices are forced to reset.
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- Send request from device(Srq):
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+ Service request from device(Srq):
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Device can request to send at commad(Global only?) stop bit.
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- keep low for 300us to request.
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+ Requesting device keeps low for 140-260us at stop bit of command.
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Keyboard Data(Register0)
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tmk