lib/serial.c

   1 /**
   2  * Copyright (C) 2009 Ubixum, Inc.
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2.1 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  17  **/
  18
  19
  20 #include <fx2regs.h>
  21 #include <fx2macros.h>
  22 #include <serial.h>
  23
  24
  25 /**
  26  * using the comp port implies that timer 2 will be used as
  27  * a baud rate generator.  (Don't use timer 2)
  28  **/
  29 void sio0_init( WORD baud_rate ) __critical { // baud_rate max should be 57600 since int=2 bytes
  30
  31     WORD hl; // hl value for reload
  32         BYTE mult; // multiplier for clock speed
  33     DWORD tmp; // scratch for mult/divide
  34
  35     // 0 = 12mhz, 1=24mhz, 2=48mhz
  36         mult = CPUFREQ == CLK_12M ? 1 :
  37            CPUFREQ == CLK_24M ? 2 : 4; // since only 3 clock speeds, fast switch instead of doing 2^clock speed pow(2,clkspd)
  38
  39         // set the clock rate
  40         // use clock 2
  41         RCLK=1;TCLK=1;
  42
  43 //    RCAP2H:L = 0xFFFF - CLKOUT / 32 x baud_rate
  44
  45     // in order to round to nearest value..
  46     // tmp * 2 // double
  47     // tmp / rate // do the divide
  48     // tmp + 1 // add one (which is like adding 1/2)
  49     // tmp / 2 // back to original rounded
  50     tmp = mult * 375000L * 2 ;
  51     tmp /= baud_rate;
  52     tmp += 1;
  53     tmp /= 2;
  54
  55     hl = 0xFFFF - (WORD)tmp;
  56
  57         RCAP2H= MSB(hl);
  58         // seems that the 24/48mhz calculations are always one less than suggested values
  59     // trm table 14-16
  60         RCAP2L= LSB(hl) + (mult>0?1:0);
  61         TR2=1; // start the timer
  62
  63         // set up the serial port
  64         SM0 = 0; SM1=1;// serial mode 1 (asyncronous)
  65         SM2 = 0 ; // has to do with receiving
  66         REN = 1 ; // to enable receiving
  67     PCON |= 0x80; // SET SMOD0, baud rate doubler
  68     TI = 1; // we send initial byte
  69
  70 }
  71
  72 char getchar() {
  73   char c;
  74   while (!RI)
  75     ;
  76   c=SBUF0;
  77   RI=0;
  78   return c;
  79 }
  80
  81 void _transchar(char c) {
  82  while ( !TI ); // wait for TI=1
  83  TI=0;
  84  SBUF0=c;
  85 }
  86
  87 void putchar (char c) {
  88   if (c=='\n') _transchar('\r'); // transmit \r\n
  89   _transchar(c);
  90   if (c == '\r' ) _transchar('\n'); // transmit \r\n
  91 }
  92