Add unmodified Teensy files

BUILD file and modifications to sanify coming soon. These are unmodified
from Teensyduino 1.37 for change tracking purposes.

Change-Id: Id55e2eba0e03260d14ea58ae4c536ae271315164
diff --git a/motors/usb/usb_serial.c b/motors/usb/usb_serial.c
new file mode 100644
index 0000000..a312176
--- /dev/null
+++ b/motors/usb/usb_serial.c
@@ -0,0 +1,305 @@
+/* Teensyduino Core Library
+ * http://www.pjrc.com/teensy/
+ * Copyright (c) 2017 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
+ * 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 "usb_dev.h"
+#include "usb_serial.h"
+#include "core_pins.h" // for yield()
+//#include "HardwareSerial.h"
+#include <string.h> // for memcpy()
+
+// defined by usb_dev.h -> usb_desc.h
+#if defined(CDC_STATUS_INTERFACE) && defined(CDC_DATA_INTERFACE)
+#if F_CPU >= 20000000
+
+uint32_t usb_cdc_line_coding[2];
+volatile uint32_t usb_cdc_line_rtsdtr_millis;
+volatile uint8_t usb_cdc_line_rtsdtr=0;
+volatile uint8_t usb_cdc_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_serial_getchar(void)
+{
+	unsigned int i;
+	int c;
+
+	if (!rx_packet) {
+		if (!usb_configuration) return -1;
+		rx_packet = usb_rx(CDC_RX_ENDPOINT);
+		if (!rx_packet) return -1;
+	}
+	i = rx_packet->index;
+	c = rx_packet->buf[i++];
+	if (i >= rx_packet->len) {
+		usb_free(rx_packet);
+		rx_packet = NULL;
+	} else {
+		rx_packet->index = i;
+	}
+	return c;
+}
+
+// peek at the next character, or -1 if nothing received
+int usb_serial_peekchar(void)
+{
+	if (!rx_packet) {
+		if (!usb_configuration) return -1;
+		rx_packet = usb_rx(CDC_RX_ENDPOINT);
+		if (!rx_packet) return -1;
+	}
+	if (!rx_packet) return -1;
+	return rx_packet->buf[rx_packet->index];
+}
+
+// number of bytes available in the receive buffer
+int usb_serial_available(void)
+{
+	int count;
+	count = usb_rx_byte_count(CDC_RX_ENDPOINT);
+	if (rx_packet) count += rx_packet->len - rx_packet->index;
+	return count;
+}
+
+// read a block of bytes to a buffer
+int usb_serial_read(void *buffer, uint32_t size)
+{
+	uint8_t *p = (uint8_t *)buffer;
+	uint32_t qty, count=0;
+
+	while (size) {
+		if (!usb_configuration) break;
+		if (!rx_packet) {
+			rx:
+			rx_packet = usb_rx(CDC_RX_ENDPOINT);
+			if (!rx_packet) break;
+			if (rx_packet->len == 0) {
+				usb_free(rx_packet);
+				goto rx;
+			}
+		}
+		qty = rx_packet->len - rx_packet->index;
+		if (qty > size) qty = size;
+		memcpy(p, rx_packet->buf + rx_packet->index, qty);
+		p += qty;
+		count += qty;
+		size -= qty;
+		rx_packet->index += qty;
+		if (rx_packet->index >= rx_packet->len) {
+			usb_free(rx_packet);
+			rx_packet = NULL;
+		}
+	}
+	return count;
+}
+
+// discard any buffered input
+void usb_serial_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(CDC_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 8
+
+// 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 70
+
+#if F_CPU == 240000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 1600)
+#elif F_CPU == 216000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 1440)
+#elif F_CPU == 192000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 1280)
+#elif F_CPU == 180000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 1200)
+#elif F_CPU == 168000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 1100)
+#elif F_CPU == 144000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 932)
+#elif F_CPU == 120000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 764)
+#elif F_CPU == 96000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 596)
+#elif F_CPU == 72000000
+  #define TX_TIMEOUT (TX_TIMEOUT_MSEC * 512)
+#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_serial_putchar(uint8_t c)
+{
+	return usb_serial_write(&c, 1);
+}
+
+
+int usb_serial_write(const void *buffer, uint32_t size)
+{
+	uint32_t ret = size;
+	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(CDC_TX_ENDPOINT) < TX_PACKET_LIMIT) {
+					tx_noautoflush = 1;
+					tx_packet = usb_malloc();
+					if (tx_packet) break;
+					tx_noautoflush = 0;
+				}
+				if (++wait_count > TX_TIMEOUT || transmit_previous_timeout) {
+					transmit_previous_timeout = 1;
+					return -1;
+				}
+				yield();
+			}
+		}
+		transmit_previous_timeout = 0;
+		len = CDC_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 >= CDC_TX_SIZE) {
+			tx_packet->len = CDC_TX_SIZE;
+			usb_tx(CDC_TX_ENDPOINT, tx_packet);
+			tx_packet = NULL;
+		}
+		usb_cdc_transmit_flush_timer = TRANSMIT_FLUSH_TIMEOUT;
+	}
+	tx_noautoflush = 0;
+	return ret;
+}
+
+int usb_serial_write_buffer_free(void)
+{
+	uint32_t len;
+
+	tx_noautoflush = 1;
+	if (!tx_packet) {
+		if (!usb_configuration ||
+		  usb_tx_packet_count(CDC_TX_ENDPOINT) >= TX_PACKET_LIMIT ||
+		  (tx_packet = usb_malloc()) == NULL) {
+			tx_noautoflush = 0;
+			return 0;
+		}
+	}
+	len = CDC_TX_SIZE - tx_packet->index;
+	// TODO: Perhaps we need "usb_cdc_transmit_flush_timer = TRANSMIT_FLUSH_TIMEOUT"
+	// added here, so the SOF interrupt can't take away the available buffer
+	// space we just promised the user could write without blocking?
+	// But does this come with other performance downsides?  Could it lead to
+	// buffer data never actually transmitting in some usage cases?  More
+	// investigation is needed.
+	// https://github.com/PaulStoffregen/cores/issues/10#issuecomment-61514955
+	tx_noautoflush = 0;
+	return len;
+}
+
+void usb_serial_flush_output(void)
+{
+	if (!usb_configuration) return;
+	tx_noautoflush = 1;
+	if (tx_packet) {
+		usb_cdc_transmit_flush_timer = 0;
+		tx_packet->len = tx_packet->index;
+		usb_tx(CDC_TX_ENDPOINT, tx_packet);
+		tx_packet = NULL;
+	} else {
+		usb_packet_t *tx = usb_malloc();
+		if (tx) {
+			usb_cdc_transmit_flush_timer = 0;
+			usb_tx(CDC_TX_ENDPOINT, tx);
+		} else {
+			usb_cdc_transmit_flush_timer = 1;
+		}
+	}
+	tx_noautoflush = 0;
+}
+
+void usb_serial_flush_callback(void)
+{
+	if (tx_noautoflush) return;
+	if (tx_packet) {
+		tx_packet->len = tx_packet->index;
+		usb_tx(CDC_TX_ENDPOINT, tx_packet);
+		tx_packet = NULL;
+	} else {
+		usb_packet_t *tx = usb_malloc();
+		if (tx) {
+			usb_tx(CDC_TX_ENDPOINT, tx);
+		} else {
+			usb_cdc_transmit_flush_timer = 1;
+		}
+	}
+}
+
+
+
+
+#endif // F_CPU
+#endif // CDC_STATUS_INTERFACE && CDC_DATA_INTERFACE