1 files changed, 180 insertions, 0 deletions

diff --git a/adb.c b/adb.c
new file mode 100644
index 000000000..e66a501b7
--- /dev/null
+++ b/adb.c
@@ -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;
+}