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  1. /*-------------------------------------------------------------------------
  2.    ser_ir_cts_rts.c - source file for serial routines
  3.  
  4.    Copyright (C) 1999, Josef Wolf <jw AT raven.inka.de>
  5.  
  6.    Revisions:
  7.    1.0  Bela Torok <bela.torok.kssg.ch> Jul. 2000
  8.    RTS / CTS protocol added
  9.  
  10.    This library is free software; you can redistribute it and/or modify it
  11.    under the terms of the GNU General Public License as published by the
  12.    Free Software Foundation; either version 2, or (at your option) any
  13.    later version.
  14.  
  15.    This library is distributed in the hope that it will be useful,
  16.    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17.    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  18.    GNU General Public License for more details.
  19.  
  20.    You should have received a copy of the GNU General Public License
  21.    along with this library; see the file COPYING. If not, write to the
  22.    Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  23.    MA 02110-1301, USA.
  24.  
  25.    As a special exception, if you link this library with other files,
  26.    some of which are compiled with SDCC, to produce an executable,
  27.    this library does not by itself cause the resulting executable to
  28.    be covered by the GNU General Public License. This exception does
  29.    not however invalidate any other reasons why the executable file
  30.    might be covered by the GNU General Public License.
  31. -------------------------------------------------------------------------*/
  32.  
  33. /* This file implements a serial interrupt handler and its supporting
  34. * routines. Compared with the existing serial.c and _ser.c it has
  35. * following advantages:
  36. * - You can specify arbitrary buffer sizes (umm, up to 255 bytes),
  37. *   so it can run on devices with _little_ memory like at89cx051.
  38. * - It won't overwrite characters which already are stored in the
  39. *   receive-/transmit-buffer.
  40. */
  41.  
  42. /* BUG: those definitions (and the #include) should be set dynamically
  43. * (while linking or at runtime) to make this file a _real_ library.
  44. */
  45.  
  46. /* RTS/CTS protocol howto:
  47.  
  48.  
  49.    Shematic of cable for RTS/CTS protocol (B. Torok - Jun. 2000)
  50.  
  51. <- DB9 female connector -><- RS232 driver/receiver -><- 8051 system ->
  52.    connect to PC             e.g. MAX232
  53.  
  54.                              RS232         TTL
  55.                              level         level
  56.  
  57.    DCD    DTR                
  58.    Pin1---Pin4              
  59.                             Transmitters/Receivers
  60.    RXD
  61.    Pin2-----------------------------<<<-------------------TXD
  62.  
  63.    TXD
  64.    Pin3----------------------------->>>-------------------RXD
  65.  
  66.    GND
  67.    Pin5---------------------------------------------------GND
  68.  
  69.    DSR    CTS
  70.    Pin6---Pin8----------------------<<<-------------------CTS (see #define CTS)
  71.  
  72.    RTS
  73.    Pin7----------------------------->>>-------------------RTS (see #define RTS)
  74. */
  75.  
  76.  
  77. #include <8051.h>
  78. #include "ser_ir.h"
  79.  
  80. #define TXBUFLEN 3
  81. #define RXBUFLEN 18      // The minimum rx buffer size for safe communications
  82.                          // is 17. (The UART in the PC has a 16-byte FIFO.)
  83. // TXBUFLEN & RXBUFLEN can be highher if rxbuf[] and txbuf[] is in xdata, max size is limited to 256!
  84.  
  85. #define THRESHOLD 16
  86. #define ENABLE    0
  87. #define DISABLE   1
  88.  
  89. #define CTS P3_6          // CTS & RTS can be assigned to any free pins
  90. #define RTS P3_7
  91.  
  92. // You might want to specify idata, pdata or xdata for the buffers
  93. static unsigned char rxbuf[RXBUFLEN], txbuf[TXBUFLEN];
  94. static unsigned char rxcnt, txcnt, rxpos, txpos;
  95. static bit busy;
  96.  
  97. void
  98. ser_init ()
  99. {
  100.   ES = 0;
  101.   rxcnt = txcnt = rxpos = txpos = 0;  // init buffers
  102.   busy = 0;
  103.   SCON = 0x50;               // mode 1 - 8-bit UART
  104.   PCON |= 0x80;              // SMOD = 1;
  105.   TMOD &= 0x0f;              // use timer 1
  106.   TMOD |= 0x20;
  107. //  TL1 = TH1 = 256 - 104;      // 600bps with 12 MHz crystal
  108. //  TL1 = TH1 = 256 - 52;      // 1200bps with 12 MHz crystal
  109. //  TL1 = TH1 = 256 - 26;      // 2400bps with 12 MHz crystal
  110.   TL1 = TH1 = 256 - 13;      // 4800bps with 12 MHz crystal
  111.  
  112.   TR1 = 1;                   // Enable timer 1
  113.   ES = 1;
  114.  
  115.   CTS = ENABLE;
  116. }
  117.  
  118. void
  119. ser_handler (void) interrupt 4
  120. {
  121.   if (RI) {
  122.     RI = 0;
  123.     /* don't overwrite chars already in buffer */
  124.     if(rxcnt < RXBUFLEN) rxbuf [(unsigned char)(rxpos + rxcnt++) % RXBUFLEN] = SBUF;
  125.     if(rxcnt >= (RXBUFLEN - THRESHOLD)) CTS = DISABLE;
  126.   }
  127.  
  128.   if (TI) {
  129.     TI = 0;
  130.     if (busy = txcnt) {   /* Assignment, _not_ comparison! */
  131.       txcnt--;
  132.       SBUF = txbuf[txpos++];
  133.       if(txpos >= TXBUFLEN) txpos = 0;
  134.     }
  135.   }
  136. }
  137.  
  138. void
  139. ser_putc (unsigned char c)
  140. {
  141.   while(txcnt >= TXBUFLEN);   // wait for room in buffer
  142.  
  143.   while(RTS == DISABLE);
  144.  
  145.   ES = 0;
  146.   if (busy) {
  147.     txbuf[(unsigned char)(txpos + txcnt++) % TXBUFLEN] = c;
  148.   } else {
  149.     SBUF = c;
  150.     busy = 1;
  151.   }
  152.   ES = 1;
  153. }
  154.  
  155. unsigned char
  156. ser_getc (void)
  157. {
  158.   unsigned char c;
  159.  
  160.   while (!rxcnt) {        // wait for a character
  161.     CTS = ENABLE;
  162.   }
  163.  
  164.   ES = 0;
  165.   rxcnt--;
  166.   c = rxbuf[rxpos++];
  167.   if (rxpos >= RXBUFLEN) rxpos = 0;
  168.   ES = 1;
  169.   return (c);
  170. }
  171.  
  172. #pragma save
  173. #pragma noinduction
  174. void
  175. ser_puts (unsigned char *s)
  176. {
  177.   unsigned char c;
  178.   while (c= *s++) {
  179.     if (c == '\n') ser_putc('\r');
  180.     ser_putc (c);
  181.   }
  182. }
  183. #pragma restore
  184.  
  185. void
  186. ser_gets (unsigned char *s, unsigned char len)
  187. {
  188.   unsigned char pos, c;
  189.  
  190.   pos = 0;
  191.   while (pos <= len) {
  192.     c = ser_getc();
  193.     if (c == '\r') continue;        // discard CR's
  194.     s[pos++] = c;
  195.     if (c == '\n') break;           // NL terminates
  196.   }
  197.   s[pos] = '\0';                  // terminate string
  198. }
  199.  
  200. unsigned char
  201. ser_can_xmt (void)
  202. {
  203.   return TXBUFLEN - txcnt;
  204. }
  205.  
  206. unsigned char
  207. ser_can_rcv (void)
  208. {
  209.   return rxcnt;
  210. }
  211.