msp/comm.c

   1 /*
   2  Copyright (C) 2012 jaseg <s@jaseg.de>
   3
   4  This program is free software; you can redistribute it and/or
   5  modify it under the terms of the GNU General Public License
   6  version 3 as published by the Free Software Foundation.
   7  */
   8
   9 #include <stdint.h>
  10 #include <stddef.h>
  11 #include <msp430.h>
  12 #include "comm.h"
  13 #include "uart_io.h"
  14
  15 void comm_loop(){
  16     static uint8_t escape_state = 0;
  17         static uint8_t state = 0;
  18     static uint16_t pos = 0;
  19     static uint16_t funcid = 0;
  20         static uint16_t crcbuf = 0;
  21         static uint8_t argbuf[ARGBUF_SIZE];
  22         static uint16_t arglen = 0;
  23
  24     uint16_t v = uart_getc_nonblocking();
  25     uint8_t c = v&0xff;
  26     v &= 0xff00;
  27     if(!v){ //a character was successfully received
  28         if(escape_state){
  29             if(c == '#'){ //FIXME
  30                 pos = 0;
  31                 return;
  32             }
  33             escape_state = 0;
  34         }else{
  35             if(c == '\\'){
  36                 escape_state = 1;
  37                 return;
  38             }
  39         }
  40                 //escape sequence handling completed. 'c' now contains the next char of the payload.
  41                 switch(state){
  42                         case 0: //receive funcid, payload length
  43                                 switch(pos){
  44                                         case 0:
  45                                                 funcid = c<<8;
  46                                                 pos++;
  47                                                 break;
  48                                         case 1:
  49                                                 funcid |= c;
  50                                                 pos++;
  51                                                 break;
  52                                         case 2:
  53                                                 arglen = c<<8;
  54                                                 pos++;
  55                                                 break;
  56                                         case 3:
  57                                                 pos = c;
  58                                                 arglen |= c;
  59                                                 state = 1;
  60                                                 break;
  61                                 }
  62                                 break;
  63                         case 1: //receive arg payload
  64                                 pos--;
  65                                 argbuf[pos] = c;
  66                                 if(pos == 0)
  67                                         state = 3;
  68                                 break;
  69                         case 2: //receive and check payload crc. finally, call the function and send the return value
  70                                 if(pos == 0){
  71                                         crcbuf = c<<8;
  72                                         pos++;
  73                                 }else{
  74                                         crcbuf |= c;
  75                                         //successfully received the crc
  76                                         //FIXME add crc checking
  77                                         if(funcid < NUM_CALLBACKS){
  78                                                 //HACK: The argument buffer is currently passed as the response buffer for ram efficiency.
  79                                                 //Only write to the response buffer *after* you are done reading from it.
  80                                                 comm_callbacks[funcid](arglen, argbuf);
  81                                         }else{
  82                                                 //FIXME error handling
  83                                         }
  84                                 }
  85                                 break;
  86                 }
  87     }
  88 }
  89
  90 void putc_escaped(char c){
  91     if(c == '\\'){
  92         uart_putc(c);
  93     }
  94     uart_putc(c);
  95 }