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/* USB Keyboard Plus Debug Channel Example for Teensy USB Development Board
* http://www.pjrc.com/teensy/usb_keyboard.html
* Copyright (c) 2009 PJRC.COM, LLC
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <avr/interrupt.h>
#include "sendchar.h"
#include "usb_debug.h"
// the time remaining before we transmit any partially full
// packet, or send a zero length packet.
volatile uint8_t debug_flush_timer = 0;
int8_t sendchar(uint8_t c) {
static uint8_t previous_timeout = 0;
uint8_t timeout, intr_state;
// if we're not online (enumerated and configured), error
if (!usb_configured()) return -1;
// interrupts are disabled so these functions can be
// used from the main program or interrupt context,
// even both in the same program!
intr_state = SREG;
cli();
UENUM = DEBUG_TX_ENDPOINT;
// if we gave up due to timeout before, don't wait again
if (previous_timeout) {
if (!(UEINTX & (1 << RWAL))) {
SREG = intr_state;
return -1;
}
previous_timeout = 0;
}
// wait for the FIFO to be ready to accept data
timeout = UDFNUML + 4;
while (1) {
// are we ready to transmit?
if (UEINTX & (1 << RWAL)) break;
SREG = intr_state;
// have we waited too long?
if (UDFNUML == timeout) {
previous_timeout = 1;
return -1;
}
// has the USB gone offline?
if (!usb_configured()) return -1;
// get ready to try checking again
intr_state = SREG;
cli();
UENUM = DEBUG_TX_ENDPOINT;
}
// actually write the byte into the FIFO
UEDATX = c;
// if this completed a packet, transmit it now!
if (!(UEINTX & (1 << RWAL))) {
UEINTX = 0x3A;
debug_flush_timer = 0;
} else {
debug_flush_timer = 2;
}
SREG = intr_state;
return 0;
}
// immediately transmit any buffered output.
void usb_debug_flush_output(void) {
uint8_t intr_state;
intr_state = SREG;
cli();
if (debug_flush_timer) {
UENUM = DEBUG_TX_ENDPOINT;
while ((UEINTX & (1 << RWAL))) {
UEDATX = 0;
}
UEINTX = 0x3A;
debug_flush_timer = 0;
}
SREG = intr_state;
}
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