usb_debug.c

   1 #include <avr/interrupt.h>
   2 #include "usb_debug.h"
   3
   4
   5 // the time remaining before we transmit any partially full
   6 // packet, or send a zero length packet.
   7 volatile uint8_t debug_flush_timer=0;
   8
   9
  10 // transmit a character.  0 returned on success, -1 on error
  11 int8_t usb_debug_putchar(uint8_t c)
  12 {
  13         static uint8_t previous_timeout=0;
  14         uint8_t timeout, intr_state;
  15
  16         // if we're not online (enumerated and configured), error
  17         if (!usb_configured()) return -1;
  18         // interrupts are disabled so these functions can be
  19         // used from the main program or interrupt context,
  20         // even both in the same program!
  21         intr_state = SREG;
  22         cli();
  23         UENUM = DEBUG_TX_ENDPOINT;
  24         // if we gave up due to timeout before, don't wait again
  25         if (previous_timeout) {
  26                 if (!(UEINTX & (1<<RWAL))) {
  27                         SREG = intr_state;
  28                         return -1;
  29                 }
  30                 previous_timeout = 0;
  31         }
  32         // wait for the FIFO to be ready to accept data
  33         timeout = UDFNUML + 4;
  34         while (1) {
  35                 // are we ready to transmit?
  36                 if (UEINTX & (1<<RWAL)) break;
  37                 SREG = intr_state;
  38                 // have we waited too long?
  39                 if (UDFNUML == timeout) {
  40                         previous_timeout = 1;
  41                         return -1;
  42                 }
  43                 // has the USB gone offline?
  44                 if (!usb_configured()) return -1;
  45                 // get ready to try checking again
  46                 intr_state = SREG;
  47                 cli();
  48                 UENUM = DEBUG_TX_ENDPOINT;
  49         }
  50         // actually write the byte into the FIFO
  51         UEDATX = c;
  52         // if this completed a packet, transmit it now!
  53         if (!(UEINTX & (1<<RWAL))) {
  54                 UEINTX = 0x3A;
  55                 debug_flush_timer = 0;
  56         } else {
  57                 debug_flush_timer = 2;
  58         }
  59         SREG = intr_state;
  60         return 0;
  61 }
  62
  63
  64 // immediately transmit any buffered output.
  65 void usb_debug_flush_output(void)
  66 {
  67         uint8_t intr_state;
  68
  69         intr_state = SREG;
  70         cli();
  71         if (debug_flush_timer) {
  72                 UENUM = DEBUG_TX_ENDPOINT;
  73                 while ((UEINTX & (1<<RWAL))) {
  74                         UEDATX = 0;
  75                 }
  76                 UEINTX = 0x3A;
  77                 debug_flush_timer = 0;
  78         }
  79         SREG = intr_state;
  80 }