i86/mtx/mtx/samples/SERIAL/s.c

   1 /****************************************************************************
   2                serial.c file for SERIAL DRIVER
   3 Each serial terminal is represented by a stty struct consisting of
   4      INPUT section = a circular buffer with incount  chars
   5     OUTPUT section = a circular buffer with outcount chars
   6 Process and interrupt handler synchronize by sleep()/wakeup()
   7 ***************************************************************************/
   8
   9 /**************** CONSTANTS ***********************/
  10 #define BUFLEN      80
  11 #define NSTTY        2    /* number of serial ports */
  12
  13 /* offset from serial ports base */
  14 #define DATA         0   /* Data reg for Rx, Tx   */
  15 #define DIVL         0   /* When used as divisor  */
  16 #define DIVH         1   /* to generate baud rate */
  17 #define IER          1   /* Interrupt Enable reg  */
  18 #define IIR          2   /* Interrupt ID rer      */
  19 #define LCR          3   /* Line Control reg      */
  20 #define MCR          4   /* Modem Control reg     */
  21 #define LSR          5   /* Line Status reg       */
  22 #define MSR          6   /* Modem Status reg      */
  23
  24 /**** The serial terminal data structure ****/
  25 typedef struct stty {
  26
  27    /* I/O port base address */
  28    int port;
  29
  30    /* input buffer */
  31    char inbuf[BUFLEN];
  32    int inhead, intail, incount;
  33
  34    /* output buffer */
  35    char outbuf[BUFLEN];
  36    int outhead, outtail, outcount;
  37
  38   // coontrol section: (erase, kill, interrupt keys, etc)
  39   // NOT shown
  40
  41 } STTY;
  42
  43 STTY stty[NSTTY];  // actual stty data structure; one per terminal
  44
  45 /************ serial ports initialization ***************/
  46
  47 char *message[2] = { "Serial Port 0 Ready\n\r\007", "Serial Port 1 Ready\n\r\007"};
  48
  49 int sinit()         // init() function
  50 {
  51   int i;
  52   STTY *t;
  53
  54   /* initialize stty[] and serial port control registers */
  55
  56   for (i = 0; i < NSTTY; i++){
  57       t = &stty[i];
  58
  59       /* initialize data structures and pointers */
  60       if (i==0)
  61           t->port = 0x3F8;    /* COM1 base address */
  62       else
  63           t->port = 0x2F8;    /* COM2 base address */
  64
  65       printf("sinit : port %x\n", t->port);
  66       t->inhead = t->intail = t->incount = 0;
  67       t->outhead = t->outtail = t->outcount = 0;
  68
  69     lock();  // CLI; no interrupts
  70       out_byte(t->port+IER,  0x00);  /* disable serial port interrupts */
  71
  72       out_byte(t->port+LCR,  0x80);  /* ready to use 3f9,3f8 as divisor */
  73       out_byte(t->port+DIVH, 0x00);
  74       out_byte(t->port+DIVL, 12);    /* divisor = 12 ===> 9600 bauds */
  75
  76       /******** term 9600 /dev/ttyS0: 8 bits/char, no parity *************/
  77       out_byte(t->port+LCR, 0x03);
  78
  79       /*******************************************************************
  80         Writing to 3fc ModemControl tells modem : DTR, then RTS ==>
  81         let modem respond as a DCE.  Here we must let the (crossed)
  82         cable tell the TVI terminal that the "DCE" has DSR and CTS.
  83         So we turn the port's DTR and RTS on.
  84       ********************************************************************/
  85
  86       out_byte(t->port+MCR, 0x0B);  /* 1011 ==> INTERRUPT, RTS, DTR on   */
  87       out_byte(t->port+IER, 0x01);  /* Enable Rx interrupt, Tx off */
  88
  89     unlock();
  90
  91     enable_irq(4-i);  // COM1: IRQ4; COM2: IRQ3
  92
  93     /* show greeting message */
  94     sputline(i, message[i]);
  95   }
  96 }
  97
  98 //==================== LOWER HALF ROUTINES (Interrupt handlers) =======================
  99 int s0handler()
 100 {
 101   shandler(0);
 102 }
 103
 104 int s1handler()
 105 {
 106   shandler(1);
 107 }
 108
 109 int shandler(port) int port;
 110 {
 111    STTY *t;
 112    int IntID, LineStatus, ModemStatus, intType, c;
 113
 114    t = &stty[port];            /* IRQ 4 interrupt : COM1 = stty[0] */
 115
 116    IntID     = in_byte(t->port+IIR);       /* read InterruptID Reg */
 117    LineStatus= in_byte(t->port+LSR);       /* read LineStatus  Reg */
 118    ModemStatus=in_byte(t->port+MSR);       /* read ModemStatus Reg */
 119
 120    intType = IntID & 7;     /* mask out all except the lowest 3 bits */
 121    switch(intType){
 122       case 6 : do_errors(t);  break;   /* 110 = errors */
 123       case 4 : do_rx(t);      break;   /* 100 = rx interrupt */
 124       case 2 : do_tx(t);      break;   /* 010 = tx interrupt */
 125       case 0 : do_modem(t);   break;   /* 000 = modem interrupt */
 126    }
 127    out_byte(0x20, 0x20);   /* reenable the 8259 controller */
 128 }
 129
 130 int do_errors() { printf("under construction\n"); }
 131
 132 int do_modem()  { printf("don't have a modem\n"); }
 133
 134 int do_rx(t) STTY *t;           /* rx interrupt */
 135 {
 136   int c;
 137
 138   c = in_byte(t->port) & 0x7F;  /* read the ASCII char from port */
 139
 140   printf("\n%x rx_interrupt : c=%c", t->port, c);
 141
 142   if (t->incount >= BUFLEN){    // if input buf is full, discard
 143     out_byte(t->port, 007);     // but sound warning beep
 144     return;
 145   }
 146
 147   t->inbuf[t->inhead++] = c;   /* put char into circular inbuf[] */
 148   t->inhead %= BUFLEN;         /* advance inhead */
 149   t->incount++;
 150
 151   wakeup(&t->incount);         // wakeup process that may be sleeping
 152 }
 153
 154 int do_tx(t) STTY *t;          // tx_interrupt
 155 {
 156   int c;
 157
 158   if (t->outcount==0){          // nothing to do
 159       out_byte(t->port+IER, 0x01);
 160       return;
 161   }
 162   c = t->outbuf[t->outtail++];
 163   t->outtail %= BUFLEN;
 164   t->outcount--;
 165
 166   out_byte(t->port, c);
 167
 168   wakeup(&t->outcount);
 169 }
 170
 171 /**************** Upper half routines CALLED BY process **************:
 172           sgetc()/sputs() which interact with Interrupt handlers
 173 **********************************************************************/
 174
 175 int sgetc(port) int port;
 176 {
 177   STTY *t;
 178   int c;
 179
 180   t = &stty[port];
 181
 182   while (t->incount==0)
 183      sleep(&t->incount);
 184
 185   lock();             /* disable interrupts */
 186       c = t->inbuf[t->intail++];
 187       t->intail %= BUFLEN;
 188       t->incount--;
 189   unlock();
 190   return(c);
 191 }
 192
 193 int sputc(port, c) int port, c;
 194 {
 195     STTY *t = &stty[port];
 196
 197     while(t->outcount==BUFLEN)
 198       sleep(&t->outcount);
 199
 200     lock();
 201     if (t->outcount==0){
 202        out_byte(t->port, c);
 203        out_byte(t->port+IER, 0x03);
 204     }
 205     else{
 206          t->outbuf[t->outhead++] = c;
 207          t->outhead %= BUFLEN;
 208          t->outcount++;
 209     }
 210     unlock();
 211 }
 212 /********************* END OF SERIAL DRIVER *************************************/
 213
 214
 215 /***** line mode functions sgetline()/sputline() based on sgetc()/sputc() ************/
 216
 217 int sgetline(port, line) int port; char *line;
 218 {
 219    while ( (*line = sgetc(port)) != '\r'){
 220           line++;
 221    }
 222    *(line) = 0;            /* change \r to null char */
 223    return strlen(line);
 224 }
 225
 226 int sputline(port, line) int port; char *line;
 227 {
 228    while (*line){
 229          sputc(port, *line);
 230          line++;
 231    }
 232 }
 233
 234 /******* User Interface fucntions to serial ports ************/
 235 int sgets()
 236 {
 237   char line[64];
 238   int port;
 239
 240   printf("enter port # (0|1):");
 241   port = getc() - '0';
 242   printf("port=%d\n", port);
 243
 244   sputline(port, "enter a line from serial terminal : ");
 245   sgetline(port, line);
 246   printf("\nline=%s\n", line);
 247   sputline(port, line);
 248   sputline(port,"\n\r");
 249 }
 250
 251 int sputs()
 252 {
 253   char line[64];
 254   int port;
 255
 256   printf("enter port # (0|1):");
 257   port = getc() - '0';
 258
 259   printf("enter a line : ");
 260   gets(line);
 261   strcat(line, "\n\r");
 262   printf("to serial port %d: line=%s\n", port, line);
 263
 264   sputline(port, line);
 265   printf("done\n");
 266 }
 267