ps2.c

   1 /*
   2 Copyright (c) 2010,2011 Jun WAKO <wakojun@gmail.com>
   3
   4 This software is licensed with a Modified BSD License.
   5 All of this is supposed to be Free Software, Open Source, DFSG-free,
   6 GPL-compatible, and OK to use in both free and proprietary applications.
   7 Additions and corrections to this file are welcome.
   8
   9
  10 Redistribution and use in source and binary forms, with or without
  11 modification, are permitted provided that the following conditions are met:
  12
  13 * Redistributions of source code must retain the above copyright
  14   notice, this list of conditions and the following disclaimer.
  15
  16 * Redistributions in binary form must reproduce the above copyright
  17   notice, this list of conditions and the following disclaimer in
  18   the documentation and/or other materials provided with the
  19   distribution.
  20
  21 * Neither the name of the copyright holders nor the names of
  22   contributors may be used to endorse or promote products derived
  23   from this software without specific prior written permission.
  24
  25 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  26 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  27 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  28 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  29 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  30 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  31 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  32 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  33 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  34 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  35 POSSIBILITY OF SUCH DAMAGE.
  36 */
  37 #include <stdbool.h>
  38 #include <avr/io.h>
  39 #include <avr/interrupt.h>
  40 #include <util/delay.h>
  41 #include "ps2.h"
  42 #include "debug.h"
  43
  44
  45 static uint8_t recv_data(void);
  46 static inline void clock_lo(void);
  47 static inline void clock_hi(void);
  48 static inline bool clock_in(void);
  49 static inline void data_lo(void);
  50 static inline void data_hi(void);
  51 static inline bool data_in(void);
  52 static inline uint16_t wait_clock_lo(uint16_t us);
  53 static inline uint16_t wait_clock_hi(uint16_t us);
  54 static inline uint16_t wait_data_lo(uint16_t us);
  55 static inline uint16_t wait_data_hi(uint16_t us);
  56 static inline void idle(void);
  57 static inline void inhibit(void);
  58
  59
  60 /*
  61 Primitive PS/2 Library for AVR
  62 ==============================
  63 Host side is only supported now.
  64
  65
  66 I/O control
  67 -----------
  68 High state is asserted by input with pull up.
  69
  70
  71 PS/2 References
  72 ---------------
  73 http://www.computer-engineering.org/ps2protocol/
  74 http://www.mcamafia.de/pdf/ibm_hitrc07.pdf
  75 */
  76
  77
  78 #define WAIT(stat, us, err) do { \
  79     if (!wait_##stat(us)) { \
  80         ps2_error = err; \
  81         goto ERROR; \
  82     } \
  83 } while (0)
  84
  85
  86 uint8_t ps2_error = PS2_ERR_NONE;
  87
  88
  89 void ps2_host_init(void)
  90 {
  91 #ifdef PS2_INT_ENABLE
  92     PS2_INT_ENABLE();
  93     idle();
  94 #else
  95     inhibit();
  96 #endif
  97 }
  98
  99 uint8_t ps2_host_send(uint8_t data)
 100 {
 101     bool parity;
 102 RETRY:
 103     parity = true;
 104     ps2_error = 0;
 105
 106     /* terminate a transmission if we have */
 107     inhibit();
 108     _delay_us(100);
 109
 110     /* start bit [1] */
 111     data_lo();
 112     clock_hi();
 113     WAIT(clock_lo, 15000, 1);
 114     /* data [2-9] */
 115     for (uint8_t i = 0; i < 8; i++) {
 116         _delay_us(15);
 117         if (data&(1<<i)) {
 118             parity = !parity;
 119             data_hi();
 120         } else {
 121             data_lo();
 122         }
 123         WAIT(clock_hi, 50, 2);
 124         WAIT(clock_lo, 50, 3);
 125     }
 126     /* parity [10] */
 127     _delay_us(15);
 128     if (parity) { data_hi(); } else { data_lo(); }
 129     WAIT(clock_hi, 50, 4);
 130     WAIT(clock_lo, 50, 5);
 131     /* stop bit [11] */
 132     _delay_us(15);
 133     data_hi();
 134     /* ack [12] */
 135     WAIT(data_lo, 50, 6);
 136     WAIT(clock_lo, 50, 7);
 137
 138     /* wait for idle state */
 139     WAIT(clock_hi, 50, 8);
 140     WAIT(data_hi, 50, 9);
 141
 142     uint8_t res = ps2_host_recv_response();
 143     if (res == 0xFE && data != 0xFE)
 144         goto RETRY;
 145
 146     inhibit();
 147     return res;
 148 ERROR:
 149     inhibit();
 150     return 0;
 151 }
 152
 153 /* receive data when host want else inhibit communication */
 154 uint8_t ps2_host_recv_response(void)
 155 {
 156     uint8_t data = 0;
 157
 158     /* terminate a transmission if we have */
 159     inhibit();
 160     _delay_us(100);
 161
 162     /* release lines(idle state) */
 163     idle();
 164
 165     /* wait start bit */
 166     wait_clock_lo(2000);
 167     data = recv_data();
 168
 169     inhibit();
 170     return data;
 171 }
 172
 173 #ifndef PS2_INT_VECT
 174 uint8_t ps2_host_recv(void)
 175 {
 176     return ps2_host_recv_response();
 177 }
 178 #else
 179 /* ring buffer to store ps/2 key data */
 180 #define PBUF_SIZE 8
 181 static uint8_t pbuf[PBUF_SIZE];
 182 static uint8_t pbuf_head = 0;
 183 static uint8_t pbuf_tail = 0;
 184 static inline void pbuf_enqueue(uint8_t data)
 185 {
 186     if (!data)
 187         return;
 188     uint8_t next = (pbuf_head + 1) % PBUF_SIZE;
 189     if (next != pbuf_tail) {
 190         pbuf[pbuf_head] = data;
 191         pbuf_head = next;
 192     } else {
 193         debug("pbuf: full\n");
 194     }
 195 }
 196 static inline uint8_t pbuf_dequeue(void)
 197 {
 198     uint8_t val = 0;
 199     uint8_t sreg = SREG;
 200     cli();
 201     if (pbuf_head != pbuf_tail) {
 202         val = pbuf[pbuf_tail];
 203         pbuf_tail = (pbuf_tail + 1) % PBUF_SIZE;
 204     }
 205     SREG = sreg;
 206     return val;
 207 }
 208
 209 /* get data received by interrupt */
 210 uint8_t ps2_host_recv(void)
 211 {
 212     return pbuf_dequeue();
 213 }
 214
 215 ISR(PS2_INT_VECT)
 216 {
 217     /* interrupt means start bit comes */
 218     pbuf_enqueue(recv_data());
 219
 220     /* release lines(idle state) */
 221     idle();
 222     _delay_us(5);
 223 }
 224 #endif
 225
 226
 227 /*
 228 static void ps2_reset(void)
 229 {
 230     ps2_host_send(0xFF);
 231     if (ps2_host_recv_response() == 0xFA) {
 232         _delay_ms(1000);
 233         ps2_host_recv_response();
 234     }
 235 }
 236 */
 237
 238 /* send LED state to keyboard */
 239 void ps2_host_set_led(uint8_t led)
 240 {
 241 #ifdef PS2_INT_DISABLE
 242     PS2_INT_DISABLE();
 243 #endif
 244     ps2_host_send(0xED);
 245     ps2_host_recv_response();
 246     ps2_host_send(led);
 247     ps2_host_recv_response();
 248 #ifdef PS2_INT_ENABLE
 249     PS2_INT_ENABLE();
 250     idle();
 251 #endif
 252 }
 253
 254
 255 /* called after start bit comes */
 256 static uint8_t recv_data(void)
 257 {
 258     uint8_t data = 0;
 259     bool parity = true;
 260     ps2_error = 0;
 261
 262     /* start bit [1] */
 263     WAIT(clock_lo, 1, 1);
 264     WAIT(data_lo, 1, 2);
 265     WAIT(clock_hi, 50, 3);
 266
 267     /* data [2-9] */
 268     for (uint8_t i = 0; i < 8; i++) {
 269         WAIT(clock_lo, 50, 4);
 270         if (data_in()) {
 271             parity = !parity;
 272             data |= (1<<i);
 273         }
 274         WAIT(clock_hi, 50, 5);
 275     }
 276
 277     /* parity [10] */
 278     WAIT(clock_lo, 50, 6);
 279     if (data_in() != parity) {
 280         ps2_error = PS2_ERR_PARITY;
 281         goto ERROR;
 282     }
 283     WAIT(clock_hi, 50, 7);
 284
 285     /* stop bit [11] */
 286     WAIT(clock_lo, 50, 8);
 287     WAIT(data_hi, 1, 9);
 288     WAIT(clock_hi, 50, 10);
 289
 290     return data;
 291 ERROR:
 292     return 0;
 293 }
 294
 295 static inline void clock_lo()
 296 {
 297     PS2_CLOCK_PORT &= ~(1<<PS2_CLOCK_BIT);
 298     PS2_CLOCK_DDR  |=  (1<<PS2_CLOCK_BIT);
 299 }
 300 static inline void clock_hi()
 301 {
 302     /* input with pull up */
 303     PS2_CLOCK_DDR  &= ~(1<<PS2_CLOCK_BIT);
 304     PS2_CLOCK_PORT |=  (1<<PS2_CLOCK_BIT);
 305 }
 306 static inline bool clock_in()
 307 {
 308     PS2_CLOCK_DDR  &= ~(1<<PS2_CLOCK_BIT);
 309     PS2_CLOCK_PORT |=  (1<<PS2_CLOCK_BIT);
 310     return PS2_CLOCK_PIN&(1<<PS2_CLOCK_BIT);
 311 }
 312 static inline void data_lo()
 313 {
 314     PS2_DATA_PORT &= ~(1<<PS2_DATA_BIT);
 315     PS2_DATA_DDR  |=  (1<<PS2_DATA_BIT);
 316 }
 317 static inline void data_hi()
 318 {
 319     /* input with pull up */
 320     PS2_DATA_DDR  &= ~(1<<PS2_DATA_BIT);
 321     PS2_DATA_PORT |=  (1<<PS2_DATA_BIT);
 322 }
 323 static inline bool data_in()
 324 {
 325     PS2_DATA_DDR  &= ~(1<<PS2_DATA_BIT);
 326     PS2_DATA_PORT |=  (1<<PS2_DATA_BIT);
 327     return PS2_DATA_PIN&(1<<PS2_DATA_BIT);
 328 }
 329
 330 static inline uint16_t wait_clock_lo(uint16_t us)
 331 {
 332     while (clock_in()  && us) { asm(""); _delay_us(1); us--; }
 333     return us;
 334 }
 335 static inline uint16_t wait_clock_hi(uint16_t us)
 336 {
 337     while (!clock_in() && us) { asm(""); _delay_us(1); us--; }
 338     return us;
 339 }
 340 static inline uint16_t wait_data_lo(uint16_t us)
 341 {
 342     while (data_in() && us)  { asm(""); _delay_us(1); us--; }
 343     return us;
 344 }
 345 static inline uint16_t wait_data_hi(uint16_t us)
 346 {
 347     while (!data_in() && us)  { asm(""); _delay_us(1); us--; }
 348     return us;
 349 }
 350
 351 /* idle state that device can send */
 352 static inline void idle(void)
 353 {
 354     clock_hi();
 355     data_hi();
 356 }
 357
 358 /* inhibit device to send */
 359 static inline void inhibit(void)
 360 {
 361     clock_lo();
 362     data_hi();
 363 }