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+/*
+Copyright 2011 Jun WAKO <wakojun@gmail.com>
+
+This software is licensed with a Modified BSD License.
+All of this is supposed to be Free Software, Open Source, DFSG-free,
+GPL-compatible, and OK to use in both free and proprietary applications.
+Additions and corrections to this file are welcome.
+
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright
+  notice, this list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright
+  notice, this list of conditions and the following disclaimer in
+  the documentation and/or other materials provided with the
+  distribution.
+
+* Neither the name of the copyright holders nor the names of
+  contributors may be used to endorse or promote products derived
+  from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#include <stdbool.h>
+#include <util/delay.h>
+#include <avr/io.h>
+#include "adb.h"
+
+
+static inline void data_lo(void);
+static inline void data_hi(void);
+static inline bool data_in(void);
+#ifdef ADB_PSW_BIT
+static inline void psw_lo(void);
+static inline void psw_hi(void);
+static inline bool psw_in(void);
+#endif
+
+static inline void attention(void);
+static inline void place_bit0(void);
+static inline void place_bit1(void);
+static inline void send_byte(uint8_t data);
+static inline bool read_bit(void);
+static inline uint8_t read_byte(void);
+static inline uint8_t wait_data_lo(uint8_t us);
+static inline uint8_t wait_data_hi(uint8_t us);
+
+
+void adb_host_init(void)
+{
+    data_hi();
+#ifdef ADB_PSW_BIT
+    psw_hi();
+#endif
+}
+
+#ifdef ADB_PSW_BIT
+bool adb_host_psw(void)
+{
+    return psw_in();
+}
+#endif
+
+uint16_t adb_host_kbd_recv(void)
+{
+    uint16_t data = 0;
+    attention();
+    send_byte(0x2C);            // Addr:Keyboard(0010), Cmd:Talk(11), Register0(00)
+    place_bit0();               // Stopbit(0)
+    if (!wait_data_lo(0xFF))    // Tlt/Stop to Start(140-260us)
+        return 0;               // No data to send
+    if (!read_bit())            // Startbit(1)
+        return -2;
+    data = read_byte();
+    data = (data<<8) | read_byte();
+    if (read_bit())             // Stopbit(0)
+        return -3;
+    return data;
+}
+
+// send state of LEDs
+void adb_host_kbd_led(uint8_t led)
+{
+    attention();
+    send_byte(0x2A);            // Addr:Keyboard(0010), Cmd:Listen(10), Register2(10)
+    place_bit0();               // Stopbit(0)
+    _delay_us(200);             // Tlt/Stop to Start
+    place_bit1();               // Startbit(1)
+    send_byte(0);               // send upper byte (not used)
+    send_byte(led&0x07);        // send lower byte (bit2: ScrollLock, bit1: CapsLock, bit0: NumLock)
+    place_bit0();               // Stopbit(0);
+}
+
+
+static inline void data_lo()
+{
+    ADB_DDR  |=  (1<<ADB_DATA_BIT);
+    ADB_PORT &= ~(1<<ADB_DATA_BIT);
+}
+static inline void data_hi()
+{
+    ADB_PORT |=  (1<<ADB_DATA_BIT);
+    ADB_DDR  &= ~(1<<ADB_DATA_BIT);
+}
+static inline bool data_in()
+{
+    ADB_PORT |=  (1<<ADB_DATA_BIT);
+    ADB_DDR  &= ~(1<<ADB_DATA_BIT);
+    return ADB_PIN&(1<<ADB_DATA_BIT);
+}
+
+#ifdef ADB_PSW_BIT
+static inline void psw_lo()
+{
+    ADB_DDR  |=  (1<<ADB_PSW_BIT);
+    ADB_PORT &= ~(1<<ADB_PSW_BIT);
+}
+static inline void psw_hi()
+{
+    ADB_PORT |=  (1<<ADB_PSW_BIT);
+    ADB_DDR  &= ~(1<<ADB_PSW_BIT);
+}
+static inline bool psw_in()
+{
+    ADB_PORT |=  (1<<ADB_PSW_BIT);
+    ADB_DDR  &= ~(1<<ADB_PSW_BIT);
+    return ADB_PIN&(1<<ADB_PSW_BIT);
+}
+#endif
+
+static inline void attention(void)
+{
+    data_lo();
+    _delay_us(700);
+    place_bit1();
+}
+
+static inline void place_bit0(void)
+{
+    data_lo();
+    _delay_us(65);
+    data_hi();
+    _delay_us(35);
+}
+
+static inline void place_bit1(void)
+{
+    data_lo();
+    _delay_us(35);
+    data_hi();
+    _delay_us(65);
+}
+
+static inline void send_byte(uint8_t data)
+{
+    for (int i = 0; i < 8; i++) {
+        if (data&(0x80>>i))
+            place_bit1();
+        else
+            place_bit0();
+    }
+}
+
+static inline bool read_bit(void)
+{
+    // ADB Bit Cells
+    //
+    // bit0: ______~~~
+    //       65    :35us
+    //
+    // bit1: ___~~~~~~
+    //       35 :65us
+    //
+    // bit0 low time: 60-70% of bit cell(42-91us)
+    // bit1 low time: 30-40% of bit cell(21-52us)
+    // bit cell time: 70-130us
+    // [from Apple IIgs Hardware Reference Second Edition]
+    //
+    // After 55us if data line is low/high then bit is 0/1.
+    // Too simple to rely on?
+    bool bit;
+    wait_data_lo(75);   // wait the beginning of bit cell
+    _delay_us(55);
+    bit = data_in();
+    wait_data_hi(36);   // wait high part of bit cell
+    return bit;
+}
+
+static inline uint8_t read_byte(void)
+{
+    uint8_t data = 0;
+    for (int i = 0; i < 8; i++) {
+        data <<= 1;
+        if (read_bit())
+            data = data | 1;
+    }
+    return data;
+}
+
+static inline uint8_t wait_data_lo(uint8_t us)
+{
+    while (data_in() && us) {
+        _delay_us(1);
+        us--;
+    }
+    return us;
+}
+
+static inline uint8_t wait_data_hi(uint8_t us)
+{
+    while (!data_in() && us) {
+        _delay_us(1);
+        us--;
+    }
+    return us;
+}
+
+
+/*
+ADB Protocol
+============
+
+Resources
+---------
+ADB - The Untold Story: Space Aliens Ate My Mouse
+    http://developer.apple.com/legacy/mac/library/#technotes/hw/hw_01.html
+Apple IIgs Hardware Reference Second Edition [p80(Chapter6 p121)]
+    ftp://ftp.apple.asimov.net/pub/apple_II/documentation/Apple%20IIgs%20Hardware%20Reference.pdf
+ADB Keycode
+    http://72.0.193.250/Documentation/macppc/adbkeycodes/
+    http://m0115.web.fc2.com/m0115.jpg
+    [Inside Macintosh volume V, pages 191-192]
+ADB Signaling
+    http://kbdbabel.sourceforge.net/doc/kbd_signaling_pcxt_ps2_adb.pdf
+ADB Overview & History
+    http://en.wikipedia.org/wiki/Apple_Desktop_Bus
+Microchip Application Note: ADB device(with code for PIC16C)
+    http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en011062
+AVR ATtiny2131 ADB to PS/2 converter(Japanese)
+    http://hp.vector.co.jp/authors/VA000177/html/KeyBoardA5DEA5CBA5A2II.html
+
+
+Pinouts
+-------
+    ADB female socket from the front:
+    __________
+    |        | <--- top
+    | 4o  o3 |
+    |2o    o1|
+    |   ==   |
+    |________| <--- bottom
+      |    |   <--- 4pins
+
+
+    ADB female socket from bottom:
+
+    ========== <--- front
+    |        |
+    |        |
+    |2o    o1|
+    |4o    o3|
+    ---------- <--- back
+
+    1: Data
+    2: Power SW(low when press Power key)
+    3: Vcc(5V)
+    4: GND
+
+
+Commands
+--------
+    ADB command is 1byte and consists of 4bit-address, 2bit-command
+    type and 2bit-register. The commands are always sent by Host.
+
+    Command format:
+    7 6 5 4 3 2 1 0
+    | | | |------------ address
+            | |-------- command type
+                | |---- register
+
+    bits                commands
+    ------------------------------------------------------
+    - - - - 0 0 0 0     Send Request(reset all devices)
+    A A A A 0 0 0 1     Flush(reset a device)
+    - - - - 0 0 1 0     Reserved
+    - - - - 0 0 1 1     Reserved
+    - - - - 0 1 - -     Reserved
+    A A A A 1 0 R R     Listen(write to a device)
+    A A A A 1 1 R R     Talk(read from a device)
+
+    The command to read keycodes from keyboard is 0x2C which
+    consist of keyboard address 2 and Talk against register 0. 
+
+    Address:
+    2:  keyboard
+    3:  mice
+
+    Registers:
+    0: application(keyobard uses this to store its data.)
+    1: application
+    2: application(keyboard uses this for LEDs and state of modifiers)
+    3: status and command
+
+
+Communication
+-------------
+    This is a minimum information for keyboard communication.
+    See "Resources" for detail.
+
+    Signaling:
+
+    ~~~~____________~~||||||||||||__~~~~~_~~|||||||||||||||__~~~~
+
+        |800us     |  |7 Command 0|  |   |  |15-64  Data  0|Stopbit(0)
+        +Attention |              |  |   +Startbit(1)
+                   +Startbit(1)   |  +Tlt(140-260us)
+                                  +stopbit(0)
+
+    Bit cells:
+
+    bit0: ______~~~
+          65    :35us
+
+    bit1: ___~~~~~~
+          35 :65us
+
+    bit0 low time: 60-70% of bit cell(42-91us)
+    bit1 low time: 30-40% of bit cell(21-52us)
+    bit cell time: 70-130us
+    [from Apple IIgs Hardware Reference Second Edition]
+
+    Criterion for bit0/1:
+    After 55us if line is low/high then bit is 0/1.
+
+    Attention & start bit:
+    Host asserts low in 560-1040us then places start bit(1).
+
+    Tlt(Stop to Start):
+    Bus stays high in 140-260us then device places start bit(1).
+
+    Global reset:
+    Host asserts low in 2.8-5.2ms. All devices are forced to reset.
+
+    Send request from device(Srq):
+    Device can request to send at commad(Global only?) stop bit.
+    keep low for 300us to request.
+
+
+Keyboard Data(Register0)
+    This 16bit data can contains two keycodes and two released flags.
+    First keycode is palced in upper byte. When one keyocode is sent,
+    lower byte is 0xFF.
+    Release flag is 1 when key is released.
+
+    1514 . . . . . 8 7 6 . . . . . 0
+     | | | | | | | | | +-+-+-+-+-+-+-   Keycode2
+     | | | | | | | | +---------------   Released2(1 when the key is released)
+     | +-+-+-+-+-+-+-----------------   Keycode1
+     +-------------------------------   Released1(1 when the key is released)
+
+    Keycodes:
+    Scancode consists of 7bit keycode and 1bit release flag.
+    Device can send two keycodes at once. If just one keycode is sent
+    keycode1 contains it and keyocode2 is 0xFF.
+
+    Power switch:
+    You can read the state from PSW line(active low) however
+    the switch has a special scancode 0x7F7F, so you can
+    also read from Data line. It uses 0xFFFF for release scancode.
+    Release code seems to delay about some 100ms. Due to Mac soft power?
+
+Keyboard LEDs & state of keys(Register2)
+    This register hold current state of three LEDs and nine keys.
+    The state of LEDs can be changed by sending Listen command.
+    
+    1514 . . . . . . 7 6 5 . 3 2 1 0
+     | | | | | | | | | | | | | | | +-   LED1(NumLock)
+     | | | | | | | | | | | | | | +---   LED2(CapsLock)
+     | | | | | | | | | | | | | +-----   LED3(ScrollLock)
+     | | | | | | | | | | +-+-+-------   Reserved
+     | | | | | | | | | +-------------   ScrollLock
+     | | | | | | | | +---------------   NumLock
+     | | | | | | | +-----------------   Apple/Command
+     | | | | | | +-------------------   Option
+     | | | | | +---------------------   Shift
+     | | | | +-----------------------   Control
+     | | | +-------------------------   Reset/Power
+     | | +---------------------------   CapsLock
+     | +-----------------------------   Delete
+     +-------------------------------   Reserved
+
+END_OF_ADB
+*/