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- // Bit-banged implementation without any use of interrupts.
- // Data pin must have external 1K pull-up resistor.
- // Operates data pin as open-collector output.
-
- #include "adb_blargg.h"
-
- #ifdef HAVE_CONFIG_H
- #include "config.h"
- #endif
-
- #include <avr/io.h>
- #include <avr/interrupt.h>
- #include <util/delay.h>
-
- // Copyright 2011 Jun WAKO <[email protected]>
- // Copyright 2013 Shay Green <[email protected]>
- // See bottom of file for license
-
- typedef uint8_t byte;
-
- // Make loop iteration take us total, including cyc overhead of loop logic
- #define delay_loop_usec( us, cyc ) \
- __builtin_avr_delay_cycles( (unsigned long) (F_CPU / 1e6 * (us) + 0.5) - (cyc) )
-
- #if !defined(ADB_PORT) || \
- !defined(ADB_PIN) || \
- !defined(ADB_DDR) || \
- !defined(ADB_DATA_BIT)
- #error
- #endif
-
- enum { data_mask = 1<<ADB_DATA_BIT };
-
- enum { adb_cmd_read = 0x2C };
- enum { adb_cmd_write = 0x28 };
-
- // gcc is very unreliable for inlining, so use macros
- #define data_lo() (ADB_DDR |= data_mask)
- #define data_hi() (ADB_DDR &= ~data_mask)
- #define data_in() (ADB_PIN & data_mask)
-
- static void place_bit( byte bit )
- {
- // 100 us bit cell time
- data_lo();
- _delay_us( 35 );
-
- // Difference between a 0 and 1 bit is just this 30us portion in the middle
- if ( bit )
- data_hi();
- _delay_us( 30 );
-
- data_hi();
- _delay_us( 35 );
- }
-
- static void place_bit0( void ) { place_bit( 0 ); }
- static void place_bit1( void ) { place_bit( 1 ); }
-
- static void send_byte( byte data )
- {
- for ( byte n = 8; n; n-- )
- {
- place_bit( data & 0x80 );
- data <<= 1;
- }
- }
-
- static void command( byte cmd )
- {
- data_lo();
- _delay_us( 800 );
- place_bit1();
- send_byte( cmd );
- place_bit0();
- }
-
- void adb_host_init( void )
- {
- // Always keep port output 0, then just toggle DDR to be GND or leave it floating (high).
- ADB_DDR &= ~data_mask;
- ADB_PORT &= ~data_mask;
-
- #ifdef ADB_PSW_BIT
- // Weak pull-up
- ADB_PORT |= (1<<ADB_PSW_BIT);
- ADB_DDR &= ~(1<<ADB_PSW_BIT);
- #endif
- }
-
- bool adb_host_psw( void )
- {
- #ifdef ADB_PSW_BIT
- return (ADB_PIN & (1<<ADB_PSW_BIT)) != 0;
- #else
- return true;
- #endif
- }
-
- // Waits while data == val, or until us timeout expires. Returns remaining time,
- // zero if timed out.
- static byte while_data( byte us, byte data )
- {
- while ( data_in() == data )
- {
- delay_loop_usec( 1 /* us period */, 7 /* cycles loop overhead */ );
- if ( !--us )
- break;
- }
- return us;
- }
-
- static byte while_lo( byte us ) { return while_data( us, 0 ); }
- static byte while_hi( byte us ) { return while_data( us, data_mask ); }
-
- static uint16_t adb_host_talk( byte cmd )
- {
- command( cmd );
- _delay_us( 5 );
- if ( !while_hi( 260 - 5 ) ) // avg 160
- return adb_host_nothing;
-
- // Receive start bit and 16 data bits.
- // Doing them all in loop allows consistent error checking
- uint16_t data = 0;
- byte n = 17;
- do
- {
- data <<= 1;
- enum { timeout = 130 }; // maximum bit cell time
-
- byte lo = while_lo( timeout );
- if ( !lo )
- goto error; // timeout
-
- byte hi = while_hi( lo );
- if ( !hi )
- goto error; // timeout
-
- if ( timeout-lo < lo-hi )
- data |= 1;
- else if ( n == 17 )
- goto error; // start bit is wrong
- }
- while ( --n );
-
- // duration must be split in two due to 255 limit
- if ( !while_lo( 255 ) && !while_lo( 351 - 255 ) )
- goto error;
-
- if ( while_hi( 91 ) )
- goto error;
-
- return data;
-
- error:
- return adb_host_error;
- }
-
- uint16_t adb_host_kbd_recv( void )
- {
- return adb_host_talk( adb_cmd_read + 0 );
- }
-
- uint16_t adb_host_kbd_modifiers( void )
- {
- return adb_host_talk( adb_cmd_read + 2 );
- }
-
- void adb_host_listen( byte cmd, byte data_h, byte data_l )
- {
- command( cmd );
- _delay_us( 200 );
-
- place_bit1();
- send_byte( data_h );
- send_byte( data_l );
- place_bit0();
- }
-
- void adb_host_kbd_led( byte led )
- {
- adb_host_listen( adb_cmd_write + 2, 0, led & 0x07 );
- }
-
- /* 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. */
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