diff options
Diffstat (limited to 'adb.c')
| -rw-r--r-- | adb.c | 180 |
1 files changed, 180 insertions, 0 deletions
@@ -0,0 +1,180 @@ +#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:2, Cmd:talk(11), Reg:0(00) + place_bit0(); // Stopbit + if (!wait_data_lo(0xFF)) // 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; +} + + +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; +} |