text: /* 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.
   *
   * Trying to understand this rather complex code?
   *
   * Kevin Cuzner wrote a simpler version, and a great blog article:
   *   http://kevincuzner.com/2014/12/12/teensy-3-1-bare-metal-writing-a-usb-driver/
   *   https://github.com/kcuzner/teensy-oscilloscope/blob/master/scope-teensy/src/usb.c
   *
   * Andy Payne wrote another relatively simple USB example for Freescale Kinetis
   *   https://github.com/payne92/bare-metal-arm
   */
  
  #include "usb_dev.h"
  #if F_CPU >= 20000000 && defined(NUM_ENDPOINTS)
  
  #include "kinetis.h"
  //#include "HardwareSerial.h"
  #include "usb_mem.h"
  #include <string.h> // for memset
  
  // This code has a known bug with compiled with -O2 optimization on gcc 5.4.1
  // https://forum.pjrc.com/threads/53574-Teensyduino-1-43-Beta-2?p=186177&viewfull=1#post186177
  #if defined(__MKL26Z64__)
  #pragma GCC optimize ("Os")
  #else
  #pragma GCC optimize ("O3")
  #endif
  
  // buffer descriptor table
  
  typedef struct {
  	uint32_t desc;
  	void * addr;
  } bdt_t;
  
  __attribute__ ((section(".usbdescriptortable"), used))
  static bdt_t table[(NUM_ENDPOINTS+1)*4];
  
  static usb_packet_t *rx_first[NUM_ENDPOINTS];
  static usb_packet_t *rx_last[NUM_ENDPOINTS];
  static usb_packet_t *tx_first[NUM_ENDPOINTS];
  static usb_packet_t *tx_last[NUM_ENDPOINTS];
  uint16_t usb_rx_byte_count_data[NUM_ENDPOINTS];
  
  static uint8_t tx_state[NUM_ENDPOINTS];
  #define TX_STATE_BOTH_FREE_EVEN_FIRST	0
  #define TX_STATE_BOTH_FREE_ODD_FIRST	1
  #define TX_STATE_EVEN_FREE		2
  #define TX_STATE_ODD_FREE		3
  #define TX_STATE_NONE_FREE_EVEN_FIRST	4
  #define TX_STATE_NONE_FREE_ODD_FIRST	5
  
  #define BDT_OWN		0x80
  #define BDT_DATA1	0x40
  #define BDT_DATA0	0x00
  #define BDT_DTS		0x08
  #define BDT_STALL	0x04
  #define BDT_PID(n)	(((n) >> 2) & 15)
  
  #define BDT_DESC(count, data)	(BDT_OWN | BDT_DTS \
  				| ((data) ? BDT_DATA1 : BDT_DATA0) \
  				| ((count) << 16))
  
  #define TX   1
  #define RX   0
  #define ODD  1
  #define EVEN 0
  #define DATA0 0
  #define DATA1 1
  #define index(endpoint, tx, odd) (((endpoint) << 2) | ((tx) << 1) | (odd))
  #define stat2bufferdescriptor(stat) (table + ((stat) >> 2))
  
  
  static union {
   struct {
    union {
     struct {
  	uint8_t bmRequestType;
  	uint8_t bRequest;
     };
  	uint16_t wRequestAndType;
    };
  	uint16_t wValue;
  	uint16_t wIndex;
  	uint16_t wLength;
   };
   struct {
  	uint32_t word1;
  	uint32_t word2;
   };
  } setup;
  
  
  #define GET_STATUS		0
  #define CLEAR_FEATURE		1
  #define SET_FEATURE		3
  #define SET_ADDRESS		5
  #define GET_DESCRIPTOR		6
  #define SET_DESCRIPTOR		7
  #define GET_CONFIGURATION	8
  #define SET_CONFIGURATION	9
  #define GET_INTERFACE		10
  #define SET_INTERFACE		11
  #define SYNCH_FRAME		12
  
  // SETUP always uses a DATA0 PID for the data field of the SETUP transaction.
  // transactions in the data phase start with DATA1 and toggle (figure 8-12, USB1.1)
  // Status stage uses a DATA1 PID.
  
  static uint8_t ep0_rx0_buf[EP0_SIZE] __attribute__ ((aligned (4)));
  static uint8_t ep0_rx1_buf[EP0_SIZE] __attribute__ ((aligned (4)));
  static const uint8_t *ep0_tx_ptr = NULL;
  static uint16_t ep0_tx_len;
  static uint8_t ep0_tx_bdt_bank = 0;
  static uint8_t ep0_tx_data_toggle = 0;
  uint8_t usb_rx_memory_needed = 0;
  
  volatile uint8_t usb_configuration = 0;
  volatile uint8_t usb_reboot_timer = 0;
  
  
  static void endpoint0_stall(void)
  {
  	USB0_ENDPT0 = USB_ENDPT_EPSTALL | USB_ENDPT_EPRXEN | USB_ENDPT_EPTXEN | USB_ENDPT_EPHSHK;
  }
  
  
  static void endpoint0_transmit(const void *data, uint32_t len)
  {
  #if 0
  	serial_print("tx0:");
  	serial_phex32((uint32_t)data);
  	serial_print(",");
  	serial_phex16(len);
  	serial_print(ep0_tx_bdt_bank ? ", odd" : ", even");
  	serial_print(ep0_tx_data_toggle ? ", d1\n" : ", d0\n");
  #endif
  	table[index(0, TX, ep0_tx_bdt_bank)].addr = (void *)data;
  	table[index(0, TX, ep0_tx_bdt_bank)].desc = BDT_DESC(len, ep0_tx_data_toggle);
  	ep0_tx_data_toggle ^= 1;
  	ep0_tx_bdt_bank ^= 1;
  }
  
  static uint8_t reply_buffer[8];
  
  static void usb_setup(void)
  {
  	const uint8_t *data = NULL;
  	uint32_t datalen = 0;
  	const usb_descriptor_list_t *list;
  	uint32_t size;
  	volatile uint8_t *reg;
  	uint8_t epconf;
  	const uint8_t *cfg;
  	int i;
  
  	switch (setup.wRequestAndType) {
  	  case 0x0500: // SET_ADDRESS
  		break;
  	  case 0x0900: // SET_CONFIGURATION
  		//serial_print("configure\n");
  		usb_configuration = setup.wValue;
  		reg = &USB0_ENDPT1;
  		cfg = usb_endpoint_config_table;
  		// clear all BDT entries, free any allocated memory...
  		for (i=4; i < (NUM_ENDPOINTS+1)*4; i++) {
  			if (table[i].desc & BDT_OWN) {
  				usb_free((usb_packet_t *)((uint8_t *)(table[i].addr) - 8));
  			}
  		}
  		// free all queued packets
  		for (i=0; i < NUM_ENDPOINTS; i++) {
  			usb_packet_t *p, *n;
  			p = rx_first[i];
  			while (p) {
  				n = p->next;
  				usb_free(p);
  				p = n;
  			}
  			rx_first[i] = NULL;
  			rx_last[i] = NULL;
  			p = tx_first[i];
  			while (p) {
  				n = p->next;
  				usb_free(p);
  				p = n;
  			}
  			tx_first[i] = NULL;
  			tx_last[i] = NULL;
  			usb_rx_byte_count_data[i] = 0;
  			switch (tx_state[i]) {
  			  case TX_STATE_EVEN_FREE:
  			  case TX_STATE_NONE_FREE_EVEN_FIRST:
  				tx_state[i] = TX_STATE_BOTH_FREE_EVEN_FIRST;
  				break;
  			  case TX_STATE_ODD_FREE:
  			  case TX_STATE_NONE_FREE_ODD_FIRST:
  				tx_state[i] = TX_STATE_BOTH_FREE_ODD_FIRST;
  				break;
  			  default:
  				break;
  			}
  		}
  		usb_rx_memory_needed = 0;
  		for (i=1; i <= NUM_ENDPOINTS; i++) {
  			epconf = *cfg++;
  			*reg = epconf;
  			reg += 4;
  #ifdef AUDIO_INTERFACE
  			if (i == AUDIO_RX_ENDPOINT) {
  				table[index(i, RX, EVEN)].addr = usb_audio_receive_buffer;
  				table[index(i, RX, EVEN)].desc = (AUDIO_RX_SIZE<<16) | BDT_OWN;
  				table[index(i, RX, ODD)].addr = usb_audio_receive_buffer;
  				table[index(i, RX, ODD)].desc = (AUDIO_RX_SIZE<<16) | BDT_OWN;
  			} else
  #endif
  			if (epconf & USB_ENDPT_EPRXEN) {
  				usb_packet_t *p;
  				p = usb_malloc();
  				if (p) {
  					table[index(i, RX, EVEN)].addr = p->buf;
  					table[index(i, RX, EVEN)].desc = BDT_DESC(64, 0);
  				} else {
  					table[index(i, RX, EVEN)].desc = 0;
  					usb_rx_memory_needed++;
  				}
  				p = usb_malloc();
  				if (p) {
  					table[index(i, RX, ODD)].addr = p->buf;
  					table[index(i, RX, ODD)].desc = BDT_DESC(64, 1);
  				} else {
  					table[index(i, RX, ODD)].desc = 0;
  					usb_rx_memory_needed++;
  				}
  			}
  			table[index(i, TX, EVEN)].desc = 0;
  			table[index(i, TX, ODD)].desc = 0;
  #ifdef AUDIO_INTERFACE
  			if (i == AUDIO_SYNC_ENDPOINT) {
  				table[index(i, TX, EVEN)].addr = &usb_audio_sync_feedback;
  				table[index(i, TX, EVEN)].desc = (3<<16) | BDT_OWN;
  			}
  #endif
  		}
  		break;
  	  case 0x0880: // GET_CONFIGURATION
  		reply_buffer[0] = usb_configuration;
  		datalen = 1;
  		data = reply_buffer;
  		break;
  	  case 0x0080: // GET_STATUS (device)
  		reply_buffer[0] = 0;
  		reply_buffer[1] = 0;
  		datalen = 2;
  		data = reply_buffer;
  		break;
  	  case 0x0082: // GET_STATUS (endpoint)
  		i = setup.wIndex & 0x7F;
  		if (i > NUM_ENDPOINTS) {
  			// TODO: do we need to handle IN vs OUT here?
  			endpoint0_stall();
  			return;
  		}
  		reply_buffer[0] = 0;
  		reply_buffer[1] = 0;
  		if (*(uint8_t *)(&USB0_ENDPT0 + i * 4) & 0x02) reply_buffer[0] = 1;
  		data = reply_buffer;
  		datalen = 2;
  		break;
  	  case 0x0102: // CLEAR_FEATURE (endpoint)
  		i = setup.wIndex & 0x7F;
  		if (i > NUM_ENDPOINTS || setup.wValue != 0) {
  			// TODO: do we need to handle IN vs OUT here?
  			endpoint0_stall();
  			return;
  		}
  		(*(uint8_t *)(&USB0_ENDPT0 + i * 4)) &= ~0x02;
  		// TODO: do we need to clear the data toggle here?
  		break;
  	  case 0x0302: // SET_FEATURE (endpoint)
  		i = setup.wIndex & 0x7F;
  		if (i > NUM_ENDPOINTS || setup.wValue != 0) {
  			// TODO: do we need to handle IN vs OUT here?
  			endpoint0_stall();
  			return;
  		}
  		(*(uint8_t *)(&USB0_ENDPT0 + i * 4)) |= 0x02;
  		// TODO: do we need to clear the data toggle here?
  		break;
  	  case 0x0680: // GET_DESCRIPTOR
  	  case 0x0681:
  		//serial_print("desc:");
  		//serial_phex16(setup.wValue);
  		//serial_print("\n");
  		for (list = usb_descriptor_list; 1; list++) {
  			if (list->addr == NULL) break;
  			//if (setup.wValue == list->wValue &&
  			//(setup.wIndex == list->wIndex) || ((setup.wValue >> 8) == 3)) {
  			if (setup.wValue == list->wValue && setup.wIndex == list->wIndex) {
  				data = list->addr;
  				if ((setup.wValue >> 8) == 3) {
  					// for string descriptors, use the descriptor's
  					// length field, allowing runtime configured
  					// length.
  					datalen = *data;
  				} else {
  					datalen = list->length;
  				}
  #if 0
  				serial_print("Desc found, ");
  				serial_phex32((uint32_t)data);
  				serial_print(",");
  				serial_phex16(datalen);
  				serial_print(",");
  				serial_phex(data[0]);
  				serial_phex(data[1]);
  				serial_phex(data[2]);
  				serial_phex(data[3]);
  				serial_phex(data[4]);
  				serial_phex(data[5]);
  				serial_print("\n");
  #endif
  				goto send;
  			}
  		}
  		//serial_print("desc: not found\n");
  		endpoint0_stall();
  		return;
  	  case 0x2221: // CDC_SET_CONTROL_LINE_STATE
  		switch (setup.wIndex) {
  #ifdef CDC_STATUS_INTERFACE
  		  case CDC_STATUS_INTERFACE:
  			usb_cdc_line_rtsdtr_millis = systick_millis_count;
  			usb_cdc_line_rtsdtr = setup.wValue;
  			break;
  #endif
  #ifdef CDC2_STATUS_INTERFACE
  		  case CDC2_STATUS_INTERFACE:
  			usb_cdc2_line_rtsdtr_millis = systick_millis_count;
  			usb_cdc2_line_rtsdtr = setup.wValue;
  			break;
  #endif
  #ifdef CDC3_STATUS_INTERFACE
  		  case CDC3_STATUS_INTERFACE:
  			usb_cdc3_line_rtsdtr_millis = systick_millis_count;
  			usb_cdc3_line_rtsdtr = setup.wValue;
  			break;
  #endif
  		}
  		//serial_print("set control line state\n");
  		break;
  #ifdef CDC_STATUS_INTERFACE
  	  case 0x2321: // CDC_SEND_BREAK
  		break;
  	  case 0x2021: // CDC_SET_LINE_CODING
  		//serial_print("set coding, waiting...\n");
  		return;
  #endif
  
  #if defined(MTP_INTERFACE)
  	case 0x64A1: // Cancel Request (PTP spec, 5.2.1, page 8)
  		// TODO: required by PTP spec
  		endpoint0_stall();
  		return;
  	case 0x66A1: // Device Reset (PTP spec, 5.2.3, page 10)
  		// TODO: required by PTP spec
  		endpoint0_stall();
  		return;
  	case 0x67A1: // Get Device Statis (PTP spec, 5.2.4, page 10)
  		// For now, always respond with status ok.
  		reply_buffer[0] = 0x4;
  		reply_buffer[1] = 0;
  		reply_buffer[2] = 0x01;
  		reply_buffer[3] = 0x20;
  		data = reply_buffer;
  		datalen = 4;
  		break;
  #endif
  
  // TODO: this does not work... why?
  #if defined(SEREMU_INTERFACE) || defined(KEYBOARD_INTERFACE)
  	  case 0x0921: // HID SET_REPORT
  		//serial_print(":)\n");
  		return;
  	  case 0x0A21: // HID SET_IDLE
  		break;
  	  // case 0xC940:
  #endif
  
  #if defined(AUDIO_INTERFACE)
  	  case 0x0B01: // SET_INTERFACE (alternate setting)
  		if (setup.wIndex == AUDIO_INTERFACE+1) {
  			usb_audio_transmit_setting = setup.wValue;
  			if (usb_audio_transmit_setting > 0) {
  				bdt_t *b = &table[index(AUDIO_TX_ENDPOINT, TX, EVEN)];
  				uint8_t state = tx_state[AUDIO_TX_ENDPOINT-1];
  				if (state) b++;
  				if (!(b->desc & BDT_OWN)) {
  					memset(usb_audio_transmit_buffer, 0, 176);
  					b->addr = usb_audio_transmit_buffer;
  					b->desc = (176 << 16) | BDT_OWN;
  					tx_state[AUDIO_TX_ENDPOINT-1] = state ^ 1;
  				}
  			}
  		} else if (setup.wIndex == AUDIO_INTERFACE+2) {
  			usb_audio_receive_setting = setup.wValue;
  		} else {
  			endpoint0_stall();
  			return;
  		}
  		break;
  	  case 0x0A81: // GET_INTERFACE (alternate setting)
  		datalen = 1;
  		data = reply_buffer;
  		if (setup.wIndex == AUDIO_INTERFACE+1) {
  			reply_buffer[0] = usb_audio_transmit_setting;
  		} else if (setup.wIndex == AUDIO_INTERFACE+2) {
  			reply_buffer[0] = usb_audio_receive_setting;
  		} else {
  			endpoint0_stall();
  			return;
  		}
  		break;
  	  case 0x0121: // SET FEATURE
  	  case 0x0221:
  	  case 0x0321:
  	  case 0x0421:
  	  	// handle these on the next packet. See usb_audio_set_feature()
  		return;
  	  case 0x81A1: // GET FEATURE
  	  case 0x82A1:
  	  case 0x83A1:
  	  case 0x84A1:
  	  	if (usb_audio_get_feature(&setup, reply_buffer, &datalen)) {
  	  		data = reply_buffer;
  	  	}
  	  	else {
  	  		endpoint0_stall();
  	  		return;
  	  	}
  		break;
  
  	  case 0x81A2: // GET_CUR (wValue=0, wIndex=interface, wLength=len)
  		if (setup.wLength >= 3) {
  			reply_buffer[0] = 44100 & 255;
  			reply_buffer[1] = 44100 >> 8;
  			reply_buffer[2] = 0;
  			datalen = 3;
  			data = reply_buffer;
  		} else {
  			endpoint0_stall();
  			return;
  		}
  		break;
  #endif
  
  #if defined(MULTITOUCH_INTERFACE)
  	  case 0x01A1:
  		if (setup.wValue == 0x0300 && setup.wIndex == MULTITOUCH_INTERFACE) {
  			reply_buffer[0] = MULTITOUCH_FINGERS;
  			data = reply_buffer;
  			datalen = 1;
  		} else if (setup.wValue == 0x0100 && setup.wIndex == MULTITOUCH_INTERFACE) {
  			memset(reply_buffer, 0, 8);
  			data = reply_buffer;
  			datalen = 8;
  		} else {
  			endpoint0_stall();
  			return;
  		}
  		break;
  #endif
  	  default:
  		endpoint0_stall();
  		return;
  	}
  	send:
  	//serial_print("setup send ");
  	//serial_phex32(data);
  	//serial_print(",");
  	//serial_phex16(datalen);
  	//serial_print("\n");
  
  	if (datalen > setup.wLength) datalen = setup.wLength;
  	size = datalen;
  	if (size > EP0_SIZE) size = EP0_SIZE;
  	endpoint0_transmit(data, size);
  	data += size;
  	datalen -= size;
  	if (datalen == 0 && size < EP0_SIZE) return;
  
  	size = datalen;
  	if (size > EP0_SIZE) size = EP0_SIZE;
  	endpoint0_transmit(data, size);
  	data += size;
  	datalen -= size;
  	if (datalen == 0 && size < EP0_SIZE) return;
  
  	ep0_tx_ptr = data;
  	ep0_tx_len = datalen;
  }
  
  
  
  //A bulk endpoint's toggle sequence is initialized to DATA0 when the endpoint
  //experiences any configuration event (configuration events are explained in
  //Sections 9.1.1.5 and 9.4.5).
  
  //Configuring a device or changing an alternate setting causes all of the status
  //and configuration values associated with endpoints in the affected interfaces
  //to be set to their default values. This includes setting the data toggle of
  //any endpoint using data toggles to the value DATA0.
  
  //For endpoints using data toggle, regardless of whether an endpoint has the
  //Halt feature set, a ClearFeature(ENDPOINT_HALT) request always results in the
  //data toggle being reinitialized to DATA0.
  
  
  
  // #define stat2bufferdescriptor(stat) (table + ((stat) >> 2))
  
  static void usb_control(uint32_t stat)
  {
  	bdt_t *b;
  	uint32_t pid, size;
  	uint8_t *buf;
  	const uint8_t *data;
  
  	b = stat2bufferdescriptor(stat);
  	pid = BDT_PID(b->desc);
  	//count = b->desc >> 16;
  	buf = b->addr;
  	//serial_print("pid:");
  	//serial_phex(pid);
  	//serial_print(", count:");
  	//serial_phex(count);
  	//serial_print("\n");
  
  	switch (pid) {
  	case 0x0D: // Setup received from host
  		//serial_print("PID=Setup\n");
  		//if (count != 8) ; // panic?
  		// grab the 8 byte setup info
  		setup.word1 = *(uint32_t *)(buf);
  		setup.word2 = *(uint32_t *)(buf + 4);
  
  		// give the buffer back
  		b->desc = BDT_DESC(EP0_SIZE, DATA1);
  		//table[index(0, RX, EVEN)].desc = BDT_DESC(EP0_SIZE, 1);
  		//table[index(0, RX, ODD)].desc = BDT_DESC(EP0_SIZE, 1);
  
  		// clear any leftover pending IN transactions
  		ep0_tx_ptr = NULL;
  		if (ep0_tx_data_toggle) {
  		}
  		//if (table[index(0, TX, EVEN)].desc & 0x80) {
  			//serial_print("leftover tx even\n");
  		//}
  		//if (table[index(0, TX, ODD)].desc & 0x80) {
  			//serial_print("leftover tx odd\n");
  		//}
  		table[index(0, TX, EVEN)].desc = 0;
  		table[index(0, TX, ODD)].desc = 0;
  		// first IN after Setup is always DATA1
  		ep0_tx_data_toggle = 1;
  
  #if 0
  		serial_print("bmRequestType:");
  		serial_phex(setup.bmRequestType);
  		serial_print(", bRequest:");
  		serial_phex(setup.bRequest);
  		serial_print(", wValue:");
  		serial_phex16(setup.wValue);
  		serial_print(", wIndex:");
  		serial_phex16(setup.wIndex);
  		serial_print(", len:");
  		serial_phex16(setup.wLength);
  		serial_print("\n");
  #endif
  		// actually "do" the setup request
  		usb_setup();
  		// unfreeze the USB, now that we're ready
  		USB0_CTL = USB_CTL_USBENSOFEN; // clear TXSUSPENDTOKENBUSY bit
  		break;
  	case 0x01:  // OUT transaction received from host
  	case 0x02:
  		//serial_print("PID=OUT\n");
  		if (setup.wRequestAndType == 0x2021 /*CDC_SET_LINE_CODING*/) {
  			int i;
  			uint32_t *line_coding = NULL;
  			switch (setup.wIndex) {
  #ifdef CDC_STATUS_INTERFACE
  			  case CDC_STATUS_INTERFACE:
  				line_coding = usb_cdc_line_coding;
  				break;
  #endif
  #ifdef CDC2_STATUS_INTERFACE
  			  case CDC2_STATUS_INTERFACE:
  				line_coding = usb_cdc2_line_coding;
  				break;
  #endif
  #ifdef CDC3_STATUS_INTERFACE
  			  case CDC3_STATUS_INTERFACE:
  				line_coding = usb_cdc3_line_coding;
  				break;
  #endif
  			}
  			if (line_coding) {
  				uint8_t *dst = (uint8_t *)line_coding;
  				//serial_print("set line coding ");
  				for (i=0; i<7; i++) {
  					//serial_phex(*buf);
  					*dst++ = *buf++;
  				}
  				//serial_phex32(line_coding[0]);
  				//serial_print("\n");
  				if (line_coding[0] == 134) usb_reboot_timer = 15;
  			}
  			endpoint0_transmit(NULL, 0);
  		}
  #ifdef KEYBOARD_INTERFACE
  		if (setup.word1 == 0x02000921 && setup.word2 == ((1<<16)|KEYBOARD_INTERFACE)) {
  			keyboard_leds = buf[0];
  			endpoint0_transmit(NULL, 0);
  		}
  #endif
  #ifdef SEREMU_INTERFACE
  		if (setup.word1 == 0x03000921 && setup.word2 == ((4<<16)|SEREMU_INTERFACE)
  		  && buf[0] == 0xA9 && buf[1] == 0x45 && buf[2] == 0xC2 && buf[3] == 0x6B) {
  			usb_reboot_timer = 5;
  			endpoint0_transmit(NULL, 0);
  		}
  #endif
  #ifdef AUDIO_INTERFACE
  		if (usb_audio_set_feature(&setup, buf)) {
  			endpoint0_transmit(NULL, 0);
  		}
  #endif
  		// give the buffer back
  		b->desc = BDT_DESC(EP0_SIZE, DATA1);
  		break;
  
  	case 0x09: // IN transaction completed to host
  		//serial_print("PID=IN:");
  		//serial_phex(stat);
  		//serial_print("\n");
  
  		// send remaining data, if any...
  		data = ep0_tx_ptr;
  		if (data) {
  			size = ep0_tx_len;
  			if (size > EP0_SIZE) size = EP0_SIZE;
  			endpoint0_transmit(data, size);
  			data += size;
  			ep0_tx_len -= size;
  			ep0_tx_ptr = (ep0_tx_len > 0 || size == EP0_SIZE) ? data : NULL;
  		}
  
  		if (setup.bRequest == 5 && setup.bmRequestType == 0) {
  			setup.bRequest = 0;
  			//serial_print("set address: ");
  			//serial_phex16(setup.wValue);
  			//serial_print("\n");
  			USB0_ADDR = setup.wValue;
  		}
  
  		break;
  	//default:
  		//serial_print("PID=unknown:");
  		//serial_phex(pid);
  		//serial_print("\n");
  	}
  	USB0_CTL = USB_CTL_USBENSOFEN; // clear TXSUSPENDTOKENBUSY bit
  }
  
  
  
  
  
  
  usb_packet_t *usb_rx(uint32_t endpoint)
  {
  	usb_packet_t *ret;
  	endpoint--;
  	if (endpoint >= NUM_ENDPOINTS) return NULL;
  	__disable_irq();
  	ret = rx_first[endpoint];
  	if (ret) {
  		rx_first[endpoint] = ret->next;
  		usb_rx_byte_count_data[endpoint] -= ret->len;
  	}
  	__enable_irq();
  	//serial_print("rx, epidx=");
  	//serial_phex(endpoint);
  	//serial_print(", packet=");
  	//serial_phex32(ret);
  	//serial_print("\n");
  	return ret;
  }
  
  static uint32_t usb_queue_byte_count(const usb_packet_t *p)
  {
  	uint32_t count=0;
  
  	__disable_irq();
  	for ( ; p; p = p->next) {
  		count += p->len;
  	}
  	__enable_irq();
  	return count;
  }
  
  // TODO: make this an inline function...
  /*
  uint32_t usb_rx_byte_count(uint32_t endpoint)
  {
  	endpoint--;
  	if (endpoint >= NUM_ENDPOINTS) return 0;
  	return usb_rx_byte_count_data[endpoint];
  	//return usb_queue_byte_count(rx_first[endpoint]);
  }
  */
  
  uint32_t usb_tx_byte_count(uint32_t endpoint)
  {
  	endpoint--;
  	if (endpoint >= NUM_ENDPOINTS) return 0;
  	return usb_queue_byte_count(tx_first[endpoint]);
  }
  
  uint32_t usb_tx_packet_count(uint32_t endpoint)
  {
  	const usb_packet_t *p;
  	uint32_t count=0;
  
  	endpoint--;
  	if (endpoint >= NUM_ENDPOINTS) return 0;
  	__disable_irq();
  	for (p = tx_first[endpoint]; p; p = p->next) count++;
  	__enable_irq();
  	return count;
  }
  
  
  // Called from usb_free, but only when usb_rx_memory_needed > 0, indicating
  // receive endpoints are starving for memory.  The intention is to give
  // endpoints needing receive memory priority over the user's code, which is
  // likely calling usb_malloc to obtain memory for transmitting.  When the
  // user is creating data very quickly, their consumption could starve reception
  // without this prioritization.  The packet buffer (input) is assigned to the
  // first endpoint needing memory.
  //
  void usb_rx_memory(usb_packet_t *packet)
  {
  	unsigned int i;
  	const uint8_t *cfg;
  
  	cfg = usb_endpoint_config_table;
  	//serial_print("rx_mem:");
  	__disable_irq();
  	for (i=1; i <= NUM_ENDPOINTS; i++) {
  #ifdef AUDIO_INTERFACE
  		if (i == AUDIO_RX_ENDPOINT) continue;
  #endif
  		if (*cfg++ & USB_ENDPT_EPRXEN) {
  			if (table[index(i, RX, EVEN)].desc == 0) {
  				table[index(i, RX, EVEN)].addr = packet->buf;
  				table[index(i, RX, EVEN)].desc = BDT_DESC(64, 0);
  				usb_rx_memory_needed--;
  				__enable_irq();
  				//serial_phex(i);
  				//serial_print(",even\n");
  				return;
  			}
  			if (table[index(i, RX, ODD)].desc == 0) {
  				table[index(i, RX, ODD)].addr = packet->buf;
  				table[index(i, RX, ODD)].desc = BDT_DESC(64, 1);
  				usb_rx_memory_needed--;
  				__enable_irq();
  				//serial_phex(i);
  				//serial_print(",odd\n");
  				return;
  			}
  		}
  	}
  	__enable_irq();
  	// we should never reach this point.  If we get here, it means
  	// usb_rx_memory_needed was set greater than zero, but no memory
  	// was actually needed.
  	usb_rx_memory_needed = 0;
  	usb_free(packet);
  	return;
  }
  
  //#define index(endpoint, tx, odd) (((endpoint) << 2) | ((tx) << 1) | (odd))
  //#define stat2bufferdescriptor(stat) (table + ((stat) >> 2))
  
  void usb_tx(uint32_t endpoint, usb_packet_t *packet)
  {
  	bdt_t *b = &table[index(endpoint, TX, EVEN)];
  	uint8_t next;
  
  	endpoint--;
  	if (endpoint >= NUM_ENDPOINTS) return;
  	__disable_irq();
  	//serial_print("txstate=");
  	//serial_phex(tx_state[endpoint]);
  	//serial_print("\n");
  	switch (tx_state[endpoint]) {
  	  case TX_STATE_BOTH_FREE_EVEN_FIRST:
  		next = TX_STATE_ODD_FREE;
  		break;
  	  case TX_STATE_BOTH_FREE_ODD_FIRST:
  		b++;
  		next = TX_STATE_EVEN_FREE;
  		break;
  	  case TX_STATE_EVEN_FREE:
  		next = TX_STATE_NONE_FREE_ODD_FIRST;
  		break;
  	  case TX_STATE_ODD_FREE:
  		b++;
  		next = TX_STATE_NONE_FREE_EVEN_FIRST;
  		break;
  	  default:
  		if (tx_first[endpoint] == NULL) {
  			tx_first[endpoint] = packet;
  		} else {
  			tx_last[endpoint]->next = packet;
  		}
  		tx_last[endpoint] = packet;
  		__enable_irq();
  		return;
  	}
  	tx_state[endpoint] = next;
  	b->addr = packet->buf;
  	b->desc = BDT_DESC(packet->len, ((uint32_t)b & 8) ? DATA1 : DATA0);
  	__enable_irq();
  }
  
  void usb_tx_isochronous(uint32_t endpoint, void *data, uint32_t len)
  {
  	bdt_t *b = &table[index(endpoint, TX, EVEN)];
  	uint8_t next, state;
  
  	endpoint--;
  	if (endpoint >= NUM_ENDPOINTS) return;
  	__disable_irq();
  	state = tx_state[endpoint];
  	if (state == 0) {
  		next = 1;
  	} else {
  		b++;
  		next = 0;
  	}
  	tx_state[endpoint] = next;
  	b->addr = data;
  	b->desc = (len << 16) | BDT_OWN;
  	__enable_irq();
  }
  
  
  
  
  void _reboot_Teensyduino_(void)
  {
  	// TODO: initialize R0 with a code....
  	__asm__ volatile("bkpt");
  	__builtin_unreachable();
  }
  
  
  
  void usb_isr(void)
  {
  	uint8_t status, stat, t;
  
  	//serial_print("isr");
  	//status = USB0_ISTAT;
  	//serial_phex(status);
  	//serial_print("\n");
  	restart:
  	status = USB0_ISTAT;
  
  	if ((status & USB_ISTAT_SOFTOK /* 04 */ )) {
  		if (usb_configuration) {
  			t = usb_reboot_timer;
  			if (t) {
  				usb_reboot_timer = --t;
  				if (!t) _reboot_Teensyduino_();
  			}
  #ifdef CDC_DATA_INTERFACE
  			t = usb_cdc_transmit_flush_timer;
  			if (t) {
  				usb_cdc_transmit_flush_timer = --t;
  				if (t == 0) usb_serial_flush_callback();
  			}
  #endif
  #ifdef CDC2_DATA_INTERFACE
  			t = usb_cdc2_transmit_flush_timer;
  			if (t) {
  				usb_cdc2_transmit_flush_timer = --t;
  				if (t == 0) usb_serial2_flush_callback();
  			}
  #endif
  #ifdef CDC3_DATA_INTERFACE
  			t = usb_cdc3_transmit_flush_timer;
  			if (t) {
  				usb_cdc3_transmit_flush_timer = --t;
  				if (t == 0) usb_serial3_flush_callback();
  			}
  #endif
  #ifdef SEREMU_INTERFACE
  			t = usb_seremu_transmit_flush_timer;
  			if (t) {
  				usb_seremu_transmit_flush_timer = --t;
  				if (t == 0) usb_seremu_flush_callback();
  			}
  #endif
  #ifdef MIDI_INTERFACE
                          usb_midi_flush_output();
  #endif
  #ifdef FLIGHTSIM_INTERFACE
  			usb_flightsim_flush_callback();
  #endif
  #ifdef MULTITOUCH_INTERFACE
  			usb_touchscreen_update_callback();
  #endif
  		}
  		USB0_ISTAT = USB_ISTAT_SOFTOK;
  	}
  
  	if ((status & USB_ISTAT_TOKDNE /* 08 */ )) {
  		uint8_t endpoint;
  		stat = USB0_STAT;
  		//serial_print("token: ep=");
  		//serial_phex(stat >> 4);
  		//serial_print(stat & 0x08 ? ",tx" : ",rx");
  		//serial_print(stat & 0x04 ? ",odd\n" : ",even\n");
  		endpoint = stat >> 4;
  		if (endpoint == 0) {
  			usb_control(stat);
  		} else {
  			bdt_t *b = stat2bufferdescriptor(stat);
  			usb_packet_t *packet = (usb_packet_t *)((uint8_t *)(b->addr) - 8);
  #if 0
  			serial_print("ep:");
  			serial_phex(endpoint);
  			serial_print(", pid:");
  			serial_phex(BDT_PID(b->desc));
  			serial_print(((uint32_t)b & 8) ? ", odd" : ", even");
  			serial_print(", count:");
  			serial_phex(b->desc >> 16);
  			serial_print("\n");
  #endif
  			endpoint--;	// endpoint is index to zero-based arrays
  
  #ifdef AUDIO_INTERFACE
  			if ((endpoint == AUDIO_TX_ENDPOINT-1) && (stat & 0x08)) {
  				unsigned int len;
  				len = usb_audio_transmit_callback();
  				if (len > 0) {
  					b = (bdt_t *)((uint32_t)b ^ 8);
  					b->addr = usb_audio_transmit_buffer;
  					b->desc = (len << 16) | BDT_OWN;
  					tx_state[endpoint] ^= 1;
  				}
  			} else if ((endpoint == AUDIO_RX_ENDPOINT-1) && !(stat & 0x08)) {
  				usb_audio_receive_callback(b->desc >> 16);
  				b->addr = usb_audio_receive_buffer;
  				b->desc = (AUDIO_RX_SIZE << 16) | BDT_OWN;
  			} else if ((endpoint == AUDIO_SYNC_ENDPOINT-1) && (stat & 0x08)) {
  				b = (bdt_t *)((uint32_t)b ^ 8);
  				b->addr = &usb_audio_sync_feedback;
  				b->desc = (3 << 16) | BDT_OWN;
  				tx_state[endpoint] ^= 1;
  			} else
  #endif
  			if (stat & 0x08) { // transmit
  				usb_free(packet);
  				packet = tx_first[endpoint];
  				if (packet) {
  					//serial_print("tx packet\n");
  					tx_first[endpoint] = packet->next;
  					b->addr = packet->buf;
  					switch (tx_state[endpoint]) {
  					  case TX_STATE_BOTH_FREE_EVEN_FIRST:
  						tx_state[endpoint] = TX_STATE_ODD_FREE;
  						break;
  					  case TX_STATE_BOTH_FREE_ODD_FIRST:
  						tx_state[endpoint] = TX_STATE_EVEN_FREE;
  						break;
  					  case TX_STATE_EVEN_FREE:
  						tx_state[endpoint] = TX_STATE_NONE_FREE_ODD_FIRST;
  						break;
  					  case TX_STATE_ODD_FREE:
  						tx_state[endpoint] = TX_STATE_NONE_FREE_EVEN_FIRST;
  						break;
  					  default:
  						break;
  					}
  					b->desc = BDT_DESC(packet->len,
  						((uint32_t)b & 8) ? DATA1 : DATA0);
  				} else {
  					//serial_print("tx no packet\n");
  					switch (tx_state[endpoint]) {
  					  case TX_STATE_BOTH_FREE_EVEN_FIRST:
  					  case TX_STATE_BOTH_FREE_ODD_FIRST:
  						break;
  					  case TX_STATE_EVEN_FREE:
  						tx_state[endpoint] = TX_STATE_BOTH_FREE_EVEN_FIRST;
  						break;
  					  case TX_STATE_ODD_FREE:
  						tx_state[endpoint] = TX_STATE_BOTH_FREE_ODD_FIRST;
  						break;
  					  default:
  						tx_state[endpoint] = ((uint32_t)b & 8) ?
  						  TX_STATE_ODD_FREE : TX_STATE_EVEN_FREE;
  						break;
  					}
  				}
  			} else { // receive
  				packet->len = b->desc >> 16;
  				if (packet->len > 0) {
  					packet->index = 0;
  					packet->next = NULL;
  					if (rx_first[endpoint] == NULL) {
  						//serial_print("rx 1st, epidx=");
  						//serial_phex(endpoint);
  						//serial_print(", packet=");
  						//serial_phex32((uint32_t)packet);
  						//serial_print("\n");
  						rx_first[endpoint] = packet;
  					} else {
  						//serial_print("rx Nth, epidx=");
  						//serial_phex(endpoint);
  						//serial_print(", packet=");
  						//serial_phex32((uint32_t)packet);
  						//serial_print("\n");
  						rx_last[endpoint]->next = packet;
  					}
  					rx_last[endpoint] = packet;
  					usb_rx_byte_count_data[endpoint] += packet->len;
  					// TODO: implement a per-endpoint maximum # of allocated
  					// packets, so a flood of incoming data on 1 endpoint
  					// doesn't starve the others if the user isn't reading
  					// it regularly
  					packet = usb_malloc();
  					if (packet) {
  						b->addr = packet->buf;
  						b->desc = BDT_DESC(64,
  							((uint32_t)b & 8) ? DATA1 : DATA0);
  					} else {
  						//serial_print("starving ");
  						//serial_phex(endpoint + 1);
  						b->desc = 0;
  						usb_rx_memory_needed++;
  					}
  				} else {
  					b->desc = BDT_DESC(64, ((uint32_t)b & 8) ? DATA1 : DATA0);
  				}
  			}
  
  		}
  		USB0_ISTAT = USB_ISTAT_TOKDNE;
  		goto restart;
  	}
  
  
  
  	if (status & USB_ISTAT_USBRST /* 01 */ ) {
  		//serial_print("reset\n");
  
  		// initialize BDT toggle bits
  		USB0_CTL = USB_CTL_ODDRST;
  		ep0_tx_bdt_bank = 0;
  
  		// set up buffers to receive Setup and OUT packets
  		table[index(0, RX, EVEN)].desc = BDT_DESC(EP0_SIZE, 0);
  		table[index(0, RX, EVEN)].addr = ep0_rx0_buf;
  		table[index(0, RX, ODD)].desc = BDT_DESC(EP0_SIZE, 0);
  		table[index(0, RX, ODD)].addr = ep0_rx1_buf;
  		table[index(0, TX, EVEN)].desc = 0;
  		table[index(0, TX, ODD)].desc = 0;
  
  		// activate endpoint 0
  		USB0_ENDPT0 = USB_ENDPT_EPRXEN | USB_ENDPT_EPTXEN | USB_ENDPT_EPHSHK;
  
  		// clear all ending interrupts
  		USB0_ERRSTAT = 0xFF;
  		USB0_ISTAT = 0xFF;
  
  		// set the address to zero during enumeration
  		USB0_ADDR = 0;
  
  		// enable other interrupts
  		USB0_ERREN = 0xFF;
  		USB0_INTEN = USB_INTEN_TOKDNEEN |
  			USB_INTEN_SOFTOKEN |
  			USB_INTEN_STALLEN |
  			USB_INTEN_ERROREN |
  			USB_INTEN_USBRSTEN |
  			USB_INTEN_SLEEPEN;
  
  		// is this necessary?
  		USB0_CTL = USB_CTL_USBENSOFEN;
  		return;
  	}
  
  
  	if ((status & USB_ISTAT_STALL /* 80 */ )) {
  		//serial_print("stall:\n");
  		USB0_ENDPT0 = USB_ENDPT_EPRXEN | USB_ENDPT_EPTXEN | USB_ENDPT_EPHSHK;
  		USB0_ISTAT = USB_ISTAT_STALL;
  	}
  	if ((status & USB_ISTAT_ERROR /* 02 */ )) {
  		uint8_t err = USB0_ERRSTAT;
  		USB0_ERRSTAT = err;
  		//serial_print("err:");
  		//serial_phex(err);
  		//serial_print("\n");
  		USB0_ISTAT = USB_ISTAT_ERROR;
  	}
  
  	if ((status & USB_ISTAT_SLEEP /* 10 */ )) {
  		//serial_print("sleep\n");
  		USB0_ISTAT = USB_ISTAT_SLEEP;
  	}
  
  }
  
  
  
  void usb_init(void)
  {
  	int i;
  
  	//serial_begin(BAUD2DIV(115200));
  	//serial_print("usb_init\n");
  
  	usb_init_serialnumber();
  
  	for (i=0; i <= NUM_ENDPOINTS*4; i++) {
  		table[i].desc = 0;
  		table[i].addr = 0;
  	}
  
  	// this basically follows the flowchart in the Kinetis
  	// Quick Reference User Guide, Rev. 1, 03/2012, page 141
  
  	// assume 48 MHz clock already running
  	// SIM - enable clock
  	SIM_SCGC4 |= SIM_SCGC4_USBOTG;
  #ifdef HAS_KINETIS_MPU
  	MPU_RGDAAC0 |= 0x03000000;
  #endif
  #if F_CPU == 180000000 || F_CPU == 216000000 || F_CPU == 256000000
  	// if using IRC48M, turn on the USB clock recovery hardware
  	USB0_CLK_RECOVER_IRC_EN = USB_CLK_RECOVER_IRC_EN_IRC_EN | USB_CLK_RECOVER_IRC_EN_REG_EN;
  	USB0_CLK_RECOVER_CTRL = USB_CLK_RECOVER_CTRL_CLOCK_RECOVER_EN |
  		USB_CLK_RECOVER_CTRL_RESTART_IFRTRIM_EN;
  #endif
  	// reset USB module
  	//USB0_USBTRC0 = USB_USBTRC_USBRESET;
  	//while ((USB0_USBTRC0 & USB_USBTRC_USBRESET) != 0) ; // wait for reset to end
  
  	// set desc table base addr
  	USB0_BDTPAGE1 = ((uint32_t)table) >> 8;
  	USB0_BDTPAGE2 = ((uint32_t)table) >> 16;
  	USB0_BDTPAGE3 = ((uint32_t)table) >> 24;
  
  	// clear all ISR flags
  	USB0_ISTAT = 0xFF;
  	USB0_ERRSTAT = 0xFF;
  	USB0_OTGISTAT = 0xFF;
  
  	//USB0_USBTRC0 |= 0x40; // undocumented bit
  
  	// enable USB
  	USB0_CTL = USB_CTL_USBENSOFEN;
  	USB0_USBCTRL = 0;
  
  	// enable reset interrupt
  	USB0_INTEN = USB_INTEN_USBRSTEN;
  
  	// enable interrupt in NVIC...
  	NVIC_SET_PRIORITY(IRQ_USBOTG, 112);
  	NVIC_ENABLE_IRQ(IRQ_USBOTG);
  
  	// enable d+ pullup
  	USB0_CONTROL = USB_CONTROL_DPPULLUPNONOTG;
  }
  
  
  #else // F_CPU < 20 MHz && defined(NUM_ENDPOINTS)
  
  void usb_init(void)
  {
  }
  
  #endif // F_CPU >= 20 MHz && defined(NUM_ENDPOINTS)
  