/*
Copyright 2011 Jun WAKO <[email protected]>

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
*/