/* 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; }