usb_seremu.c

/* Teensyduino Core Library
 * http://www.pjrc.com/teensy/
 * Copyright (c) 2013 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:
 *
 * 1. The above copyright notice and this permission notice shall be 
 * included in all copies or substantial portions of the Software.
 *
 * 2. If the Software is incorporated into a build system that allows 
 * selection among a list of target devices, then similar target
 * devices manufactured by PJRC.COM must be included in the list of
 * target devices and selectable in the same manner.
 *
 * 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
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 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

//#include "mk20dx128.h"
#include "usb_dev.h"
#include "usb_seremu.h"
#include "core_pins.h" // for yield()
//#include "HardwareSerial.h"

#ifdef SEREMU_INTERFACE // defined by usb_dev.h -> usb_desc.h

volatile uint8_t usb_seremu_transmit_flush_timer=0;

static usb_packet_t *rx_packet=NULL;
static usb_packet_t *tx_packet=NULL;
static volatile uint8_t tx_noautoflush=0;

#define TRANSMIT_FLUSH_TIMEOUT	5   /* in milliseconds */


// get the next character, or -1 if nothing received
int usb_seremu_getchar(void)
{
	unsigned int i;
	int c;

	while (1) {
		if (!usb_configuration) return -1;
		if (!rx_packet) rx_packet = usb_rx(SEREMU_RX_ENDPOINT);
		if (!rx_packet) return -1;
		i = rx_packet->index;
		c = rx_packet->buf[i++];
		if (c) {
			if (i >= rx_packet->len) {
				usb_free(rx_packet);
				rx_packet = NULL;
			} else {
				rx_packet->index = i;
			}
			return c;
		}
		usb_free(rx_packet);
		rx_packet = NULL;
	}
}

// peek at the next character, or -1 if nothing received
int usb_seremu_peekchar(void)
{
	int c;

	while (1) {
		if (!usb_configuration) return -1;
		if (!rx_packet) rx_packet = usb_rx(SEREMU_RX_ENDPOINT);
		if (!rx_packet) return -1;
		c = rx_packet->buf[rx_packet->index];
		if (c) return c;
		usb_free(rx_packet);
		rx_packet = NULL;
	}
}

// number of bytes available in the receive buffer
int usb_seremu_available(void)
{
	int i, len, count;

	if (!rx_packet) {
		if (usb_configuration) rx_packet = usb_rx(SEREMU_RX_ENDPOINT);
		if (!rx_packet) return 0;
	}
	len = rx_packet->len;
	i = rx_packet->index;
	count = 0;
	for (i = rx_packet->index; i < len; i++) {
		if (rx_packet->buf[i] == 0) break;
		count++;
	}
	if (count == 0) {
		usb_free(rx_packet);
		rx_packet = NULL;
	}
	return count;
}


// discard any buffered input
void usb_seremu_flush_input(void)
{
	usb_packet_t *rx;

	if (!usb_configuration) return;
	if (rx_packet) {
		usb_free(rx_packet);
		rx_packet = NULL;
	}
	while (1) {
		rx = usb_rx(SEREMU_RX_ENDPOINT);
		if (!rx) break;
		usb_free(rx);
	}
}



// Maximum number of transmit packets to queue so we don't starve other endpoints for memory
#define TX_PACKET_LIMIT 6

// When the PC isn't listening, how long do we wait before discarding data?  If this is
// too short, we risk losing data during the stalls that are common with ordinary desktop
// software.  If it's too long, we stall the user's program when no software is running.
#define TX_TIMEOUT_MSEC 30

#if F_CPU == 96000000
  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 596)
#elif F_CPU == 48000000
  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 428)
#elif F_CPU == 24000000
  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 262)
#endif

// When we've suffered the transmit timeout, don't wait again until the computer
// begins accepting data.  If no software is running to receive, we'll just discard
// data as rapidly as Serial.print() can generate it, until there's something to
// actually receive it.
static uint8_t transmit_previous_timeout=0;


// transmit a character.  0 returned on success, -1 on error
int usb_seremu_putchar(uint8_t c)
{
	return usb_seremu_write(&c, 1);
}


int usb_seremu_write(const void *buffer, uint32_t size)
{
#if 1
	uint32_t len;
	uint32_t wait_count;
	const uint8_t *src = (const uint8_t *)buffer;
	uint8_t *dest;

	tx_noautoflush = 1;
	while (size > 0) {
		if (!tx_packet) {
			wait_count = 0;
			while (1) {
				if (!usb_configuration) {
					tx_noautoflush = 0;
					return -1;
				}
				if (usb_tx_packet_count(SEREMU_TX_ENDPOINT) < TX_PACKET_LIMIT) {
					tx_noautoflush = 1;
					tx_packet = usb_malloc();
					if (tx_packet) break;
				}
				if (++wait_count > TX_TIMEOUT || transmit_previous_timeout) {
					transmit_previous_timeout = 1;
					tx_noautoflush = 0;
					return -1;
				}
				tx_noautoflush = 0;
				yield();
				tx_noautoflush = 1;
			}
		}
		transmit_previous_timeout = 0;
		len = SEREMU_TX_SIZE - tx_packet->index;
		if (len > size) len = size;
		dest = tx_packet->buf + tx_packet->index;
		tx_packet->index += len;
		size -= len;
		while (len-- > 0) *dest++ = *src++;
		if (tx_packet->index < SEREMU_TX_SIZE) {
			usb_seremu_transmit_flush_timer = TRANSMIT_FLUSH_TIMEOUT;
		} else {
			tx_packet->len = SEREMU_TX_SIZE;
			usb_seremu_transmit_flush_timer = 0;
			usb_tx(SEREMU_TX_ENDPOINT, tx_packet);
			tx_packet = NULL;
		}
	}
	tx_noautoflush = 0;
	return 0;
#endif
}

void usb_seremu_flush_output(void)
{
	int i;

	if (!usb_configuration) return;
	//serial_print("usb_serial_flush_output\n");
	if (tx_packet && tx_packet->index > 0) {
		usb_seremu_transmit_flush_timer = 0;
		for (i = tx_packet->index; i < SEREMU_TX_SIZE; i++) {
			tx_packet->buf[i] = 0;
		}
		tx_packet->len = SEREMU_TX_SIZE;
		usb_tx(SEREMU_TX_ENDPOINT, tx_packet);
		tx_packet = NULL;
	}
	// while (usb_tx_byte_count(SEREMU_TX_ENDPOINT) > 0) ; // wait
}

void usb_seremu_flush_callback(void)
{
	int i;
	//serial_print("C");
	if (tx_noautoflush) return;
	//serial_print("usb_flush_callback \n");
	for (i = tx_packet->index; i < SEREMU_TX_SIZE; i++) {
		tx_packet->buf[i] = 0;
	}
	tx_packet->len = SEREMU_TX_SIZE;
	usb_tx(SEREMU_TX_ENDPOINT, tx_packet);
	tx_packet = NULL;
	//serial_print("usb_flush_callback end\n");
}

#endif // SEREMU_INTERFACE