protocol/ps2_usart.c

   1 /*
   2 Copyright 2010,2011,2012,2013 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
  38 /*
  39  * PS/2 protocol USART version
  40  */
  41
  42 #include <stdbool.h>
  43 #include <avr/io.h>
  44 #include <avr/interrupt.h>
  45 #include <util/delay.h>
  46 #include "ps2.h"
  47 #include "debug.h"
  48
  49
  50 #define WAIT(stat, us, err) do { \
  51     if (!wait_##stat(us)) { \
  52         ps2_error = err; \
  53         goto ERROR; \
  54     } \
  55 } while (0)
  56
  57
  58 uint8_t ps2_error = PS2_ERR_NONE;
  59
  60
  61 static inline uint8_t pbuf_dequeue(void);
  62 static inline void pbuf_enqueue(uint8_t data);
  63 static inline bool pbuf_has_data(void);
  64 static inline void pbuf_clear(void);
  65
  66
  67 void ps2_host_init(void)
  68 {
  69     idle(); // without this many USART errors occur when cable is disconnected
  70     PS2_USART_INIT();
  71     PS2_USART_RX_INT_ON();
  72     // POR(150-2000ms) plus BAT(300-500ms) may take 2.5sec([3]p.20)
  73     //_delay_ms(2500);
  74 }
  75
  76 uint8_t ps2_host_send(uint8_t data)
  77 {
  78     bool parity = true;
  79     ps2_error = PS2_ERR_NONE;
  80
  81     PS2_USART_OFF();
  82
  83     /* terminate a transmission if we have */
  84     inhibit();
  85     _delay_us(100); // [4]p.13
  86
  87     /* 'Request to Send' and Start bit */
  88     data_lo();
  89     clock_hi();
  90     WAIT(clock_lo, 10000, 10);   // 10ms [5]p.50
  91
  92     /* Data bit[2-9] */
  93     for (uint8_t i = 0; i < 8; i++) {
  94         _delay_us(15);
  95         if (data&(1<<i)) {
  96             parity = !parity;
  97             data_hi();
  98         } else {
  99             data_lo();
 100         }
 101         WAIT(clock_hi, 50, 2);
 102         WAIT(clock_lo, 50, 3);
 103     }
 104
 105     /* Parity bit */
 106     _delay_us(15);
 107     if (parity) { data_hi(); } else { data_lo(); }
 108     WAIT(clock_hi, 50, 4);
 109     WAIT(clock_lo, 50, 5);
 110
 111     /* Stop bit */
 112     _delay_us(15);
 113     data_hi();
 114
 115     /* Ack */
 116     WAIT(data_lo, 50, 6);
 117     WAIT(clock_lo, 50, 7);
 118
 119     /* wait for idle state */
 120     WAIT(clock_hi, 50, 8);
 121     WAIT(data_hi, 50, 9);
 122
 123     idle();
 124     PS2_USART_INIT();
 125     PS2_USART_RX_INT_ON();
 126     return ps2_host_recv_response();
 127 ERROR:
 128     idle();
 129     PS2_USART_INIT();
 130     PS2_USART_RX_INT_ON();
 131     return 0;
 132 }
 133
 134 uint8_t ps2_host_recv_response(void)
 135 {
 136     // Command may take 25ms/20ms at most([5]p.46, [3]p.21)
 137     uint8_t retry = 25;
 138     while (retry-- && !pbuf_has_data()) {
 139         _delay_ms(1);
 140     }
 141     return pbuf_dequeue();
 142 }
 143
 144 uint8_t ps2_host_recv(void)
 145 {
 146     if (pbuf_has_data()) {
 147         ps2_error = PS2_ERR_NONE;
 148         return pbuf_dequeue();
 149     } else {
 150         ps2_error = PS2_ERR_NODATA;
 151         return 0;
 152     }
 153 }
 154
 155 ISR(PS2_USART_RX_VECT)
 156 {
 157     // TODO: request RESEND when error occurs?
 158     uint8_t error = PS2_USART_ERROR;    // USART error should be read before data
 159     uint8_t data = PS2_USART_RX_DATA;
 160     if (!error) {
 161         pbuf_enqueue(data);
 162     } else {
 163         xprintf("PS2 USART error: %02X data: %02X\n", error, data);
 164     }
 165 }
 166
 167 /* send LED state to keyboard */
 168 void ps2_host_set_led(uint8_t led)
 169 {
 170     ps2_host_send(0xED);
 171     ps2_host_send(led);
 172 }
 173
 174
 175 /*--------------------------------------------------------------------
 176  * Ring buffer to store scan codes from keyboard
 177  *------------------------------------------------------------------*/
 178 #define PBUF_SIZE 32
 179 static uint8_t pbuf[PBUF_SIZE];
 180 static uint8_t pbuf_head = 0;
 181 static uint8_t pbuf_tail = 0;
 182 static inline void pbuf_enqueue(uint8_t data)
 183 {
 184     uint8_t sreg = SREG;
 185     cli();
 186     uint8_t next = (pbuf_head + 1) % PBUF_SIZE;
 187     if (next != pbuf_tail) {
 188         pbuf[pbuf_head] = data;
 189         pbuf_head = next;
 190     } else {
 191         debug("pbuf: full\n");
 192     }
 193     SREG = sreg;
 194 }
 195 static inline uint8_t pbuf_dequeue(void)
 196 {
 197     uint8_t val = 0;
 198
 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
 207     return val;
 208 }
 209 static inline bool pbuf_has_data(void)
 210 {
 211     uint8_t sreg = SREG;
 212     cli();
 213     bool has_data = (pbuf_head != pbuf_tail);
 214     SREG = sreg;
 215     return has_data;
 216 }
 217 static inline void pbuf_clear(void)
 218 {
 219     uint8_t sreg = SREG;
 220     cli();
 221     pbuf_head = pbuf_tail = 0;
 222     SREG = sreg;
 223 }