protocol/pjrc/usb_debug.c

   1 /* USB Keyboard Plus Debug Channel Example for Teensy USB Development Board
   2  * http://www.pjrc.com/teensy/usb_keyboard.html
   3  * Copyright (c) 2009 PJRC.COM, LLC
   4  *
   5  * Permission is hereby granted, free of charge, to any person obtaining a copy
   6  * of this software and associated documentation files (the "Software"), to deal
   7  * in the Software without restriction, including without limitation the rights
   8  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   9  * copies of the Software, and to permit persons to whom the Software is
  10  * furnished to do so, subject to the following conditions:
  11  *
  12  * The above copyright notice and this permission notice shall be included in
  13  * all copies or substantial portions of the Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  18  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  21  * THE SOFTWARE.
  22  */
  23
  24 #include <avr/interrupt.h>
  25 #include "sendchar.h"
  26 #include "usb_debug.h"
  27
  28
  29 // the time remaining before we transmit any partially full
  30 // packet, or send a zero length packet.
  31 volatile uint8_t debug_flush_timer=0;
  32
  33
  34 int8_t sendchar(uint8_t c)
  35 {
  36         static uint8_t previous_timeout=0;
  37         uint8_t timeout, intr_state;
  38
  39         // if we're not online (enumerated and configured), error
  40         if (!usb_configured()) return -1;
  41         // interrupts are disabled so these functions can be
  42         // used from the main program or interrupt context,
  43         // even both in the same program!
  44         intr_state = SREG;
  45         cli();
  46         UENUM = DEBUG_TX_ENDPOINT;
  47         // if we gave up due to timeout before, don't wait again
  48         if (previous_timeout) {
  49                 if (!(UEINTX & (1<<RWAL))) {
  50                         SREG = intr_state;
  51                         return -1;
  52                 }
  53                 previous_timeout = 0;
  54         }
  55         // wait for the FIFO to be ready to accept data
  56         timeout = UDFNUML + 4;
  57         while (1) {
  58                 // are we ready to transmit?
  59                 if (UEINTX & (1<<RWAL)) break;
  60                 SREG = intr_state;
  61                 // have we waited too long?
  62                 if (UDFNUML == timeout) {
  63                         previous_timeout = 1;
  64                         return -1;
  65                 }
  66                 // has the USB gone offline?
  67                 if (!usb_configured()) return -1;
  68                 // get ready to try checking again
  69                 intr_state = SREG;
  70                 cli();
  71                 UENUM = DEBUG_TX_ENDPOINT;
  72         }
  73         // actually write the byte into the FIFO
  74         UEDATX = c;
  75         // if this completed a packet, transmit it now!
  76         if (!(UEINTX & (1<<RWAL))) {
  77                 UEINTX = 0x3A;
  78                 debug_flush_timer = 0;
  79         } else {
  80                 debug_flush_timer = 2;
  81         }
  82         SREG = intr_state;
  83         return 0;
  84 }
  85
  86 // immediately transmit any buffered output.
  87 void usb_debug_flush_output(void)
  88 {
  89         uint8_t intr_state;
  90
  91         intr_state = SREG;
  92         cli();
  93         if (debug_flush_timer) {
  94                 UENUM = DEBUG_TX_ENDPOINT;
  95                 while ((UEINTX & (1<<RWAL))) {
  96                         UEDATX = 0;
  97                 }
  98                 UEINTX = 0x3A;
  99                 debug_flush_timer = 0;
 100         }
 101         SREG = intr_state;
 102 }