- /*
- Copyright 2018 Jun WAKO <wakojun@gmail.com>
- Copyright 2016 Ethan Apodaca <papodaca@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 <avr/interrupt.h>
- #include <util/delay.h>
- #include "xt.h"
- #include "wait.h"
- #include "debug.h"
-
- static inline uint8_t pbuf_dequeue(void);
- static inline void pbuf_enqueue(uint8_t data);
- static inline bool pbuf_has_data(void);
- static inline void pbuf_clear(void);
-
- void xt_host_init(void) {
- XT_INT_INIT();
- XT_INT_OFF();
-
- /* hard reset */
- #ifdef XT_RESET
- XT_RESET();
- #endif
-
- /* soft reset: pull clock line down for 20ms */
- XT_DATA_LO();
- XT_CLOCK_LO();
- _delay_ms(20);
-
- /* input mode with pullup */
- XT_CLOCK_IN();
- XT_DATA_IN();
-
- XT_INT_ON();
- }
-
- /* get data received by interrupt */
- uint8_t xt_host_recv(void) {
- if (pbuf_has_data()) {
- return pbuf_dequeue();
- } else {
- return 0;
- }
- }
-
- ISR(XT_INT_VECT) {
- /*
- * XT signal format consits of 10 or 9 clocks and sends start bits and 8-bit data,
- * which should be read on falling edge of clock.
- *
- * start(0), start(1), bit0, bit1, bit2, bit3, bit4, bit5, bit6, bit7
- *
- * Original IBM XT keyboard sends start(0) bit while some of clones don't.
- * Start(0) bit is read as low on data line while start(1) as high.
- *
- * https://github.com/tmk/tmk_keyboard/wiki/IBM-PC-XT-Keyboard-Protocol
- */
- static enum { START, BIT0, BIT1, BIT2, BIT3, BIT4, BIT5, BIT6, BIT7 } state = START;
- static uint8_t data = 0;
-
- uint8_t dbit = XT_DATA_READ();
-
- // This is needed if using PCINT which can be called on both falling and rising edge
- // if (XT_CLOCK_READ()) return;
-
- switch (state) {
- case START:
- // ignore start(0) bit
- if (!dbit) return;
- break;
- case BIT0 ... BIT7:
- data >>= 1;
- if (dbit) data |= 0x80;
- break;
- }
- if (state++ == BIT7) {
- pbuf_enqueue(data);
- state = START;
- data = 0;
- }
- return;
- }
-
- /*--------------------------------------------------------------------
- * Ring buffer to store scan codes from keyboard
- *------------------------------------------------------------------*/
- #define PBUF_SIZE 32
- static uint8_t pbuf[PBUF_SIZE];
- static uint8_t pbuf_head = 0;
- static uint8_t pbuf_tail = 0;
- static inline void pbuf_enqueue(uint8_t data) {
- uint8_t sreg = SREG;
- cli();
- uint8_t next = (pbuf_head + 1) % PBUF_SIZE;
- if (next != pbuf_tail) {
- pbuf[pbuf_head] = data;
- pbuf_head = next;
- } else {
- dprintf("pbuf: full\n");
- }
- SREG = sreg;
- }
- static inline uint8_t pbuf_dequeue(void) {
- uint8_t val = 0;
-
- uint8_t sreg = SREG;
- cli();
- if (pbuf_head != pbuf_tail) {
- val = pbuf[pbuf_tail];
- pbuf_tail = (pbuf_tail + 1) % PBUF_SIZE;
- }
- SREG = sreg;
-
- return val;
- }
- static inline bool pbuf_has_data(void) {
- uint8_t sreg = SREG;
- cli();
- bool has_data = (pbuf_head != pbuf_tail);
- SREG = sreg;
- return has_data;
- }
- static inline void pbuf_clear(void) {
- uint8_t sreg = SREG;
- cli();
- pbuf_head = pbuf_tail = 0;
- SREG = sreg;
- }
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