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#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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