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