teensy-usbhost/serial.cpp

/* USB EHCI Host for Teensy 3.6
 * Copyright 2017 Paul Stoffregen (paul@pjrc.com)
 *
 * 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.
 *
 * Note: special thanks to the Linux kernel for the CH341's method of operation, particularly how the baud rate is encoded.
 */

#include <Arduino.h>
#include "USBHost_t36.h"  // Read this header first for key info

#define print   USBHost::print_
#define println USBHost::println_

//#define ENABLE_DEBUG_PINS

#ifdef ENABLE_DEBUG_PINS
#define debugDigitalToggle(pin)  {digitalWriteFast(pin, !digitalReadFast(pin));}
#define debugDigitalWrite(pin, state) {digitalWriteFast(pin, state);}
#else
#define debugDigitalToggle(pin)  {;}
#define debugDigitalWrite(pin, state) {;}
#endif

/************************************************************/
//  Define mapping VID/PID - to Serial Device type.
/************************************************************/
USBSerial::product_vendor_mapping_t USBSerial::pid_vid_mapping[] = {
	// FTDI mappings. 
	{0x0403, 0x6001, USBSerial::FTDI},

	// PL2303
	{0x67B,0x2303, USBSerial::PL2303}, 

	// CH341
	{0x4348, 0x5523, USBSerial::CH341 },
	{0x1a86, 0x7523, USBSerial::CH341 },
	{0x1a86, 0x5523, USBSerial::CH341 },

	// Silex CP210...
	{0x10c4, 0xea60, USBSerial::CP210X }
};


/************************************************************/
//  Initialization and claiming of devices & interfaces
/************************************************************/

void USBSerial::init()
{
	contribute_Pipes(mypipes, sizeof(mypipes)/sizeof(Pipe_t));
	contribute_Transfers(mytransfers, sizeof(mytransfers)/sizeof(Transfer_t));
	contribute_String_Buffers(mystring_bufs, sizeof(mystring_bufs)/sizeof(strbuf_t));
	driver_ready_for_device(this);
	format_ = USBHOST_SERIAL_8N1;
}

bool USBSerial::claim(Device_t *dev, int type, const uint8_t *descriptors, uint32_t len)
{
	// only claim at interface level
	println("USBSerial claim this=", (uint32_t)this, HEX);
	print("vid=", dev->idVendor, HEX);
	print(", pid=", dev->idProduct, HEX);
	print(", bDeviceClass = ", dev->bDeviceClass);
   	print(", bDeviceSubClass = ", dev->bDeviceSubClass);
   	println(", bDeviceProtocol = ", dev->bDeviceProtocol);
	print_hexbytes(descriptors, len);
	if (type == 0) {
		//---------------------------------------------------------------------
		// CDCACM
		if ((dev->bDeviceClass == 2) && (dev->bDeviceSubClass == 0)) {
			// It is a communication device see if we can extract the data... 
			// Try some ttyACM types? 
			// This code may be similar to MIDI code. 
			// But first pass see if we can simply look at the interface...
			// Lets walk through end points and see if we 
			// can find an RX and TX bulk transfer end point.
			// 0  1  2  3  4  5  6  7  8 *9 10  1  2  3 *4  5  6  7 *8  9 20  1  2 *3  4  5  6  7  8  9*30  1  2  3  4  5  6  7  8 *9 40  1  2  3  4  5 *6  7  8  9 50  1  2 
			// USB2AX
			//09 04 00 00 01 02 02 01 00 05 24 00 10 01 04 24 02 06 05 24 06 00 01 07 05 82 03 08 00 FF 09 04 01 00 02 0A 00 00 00 07 05 04 02 10 00 01 07 05 83 02 10 00 01
			//09 04 01 00 02 0A 00 00 00 07 05 04 02 10 00 01 07 05 83 02 10 00 01 
		    // Teensy 3.6
		    //09 04 00 00 01 02 02 01 00 05 24 00 10 01 05 24 01 01 01 04 24 02 06 05 24 06 00 01 07 05 82 03 10 00 40 09 04 01 00 02 0A 00 00 00 07 05 03 02 40 00 00 07 05 84 02 40 00 00  
		    //09 04 01 00 02 0A 00 00 00 07 05 03 02 40 00 00 07 05 84 02 40 00 00 
			const uint8_t *p = descriptors;
			const uint8_t *end = p + len;

			if (p[0] != 9 || p[1] != 4) return false; // interface descriptor
			//println("  bInterfaceClass=", p[5]);
			//println("  bInterfaceSubClass=", p[6]);
			if (p[5] != 2) return false; // bInterfaceClass: 2 Communications
			if (p[6] != 2) return false; // bInterfaceSubClass: 2 serial 
			p += 9;
			println("  Interface is Serial");
			uint8_t rx_ep = 0;
			uint8_t tx_ep = 0;
			uint16_t rx_size = 0;
			uint16_t tx_size = 0;
			interface = 0;	// clear out any interface numbers passed in. 

			while (p < end) {
				len = *p;
				if (len < 4) return false; 
				if (p + len > end) return false; // reject if beyond end of data
				uint32_t type = p[1];
				//println("type: ", type);
				// Unlike Audio, we need to look at Interface as our endpoints are after them...
				if (type == 4 ) { // Interface - lets remember it's number...
					interface = p[2];
					println("    Interface: ", interface);
				}
				else if (type == 0x24) {  // 0x24 = CS_INTERFACE, 
					uint32_t subtype = p[2];
					print("    CS_INTERFACE - subtype: ", subtype);
					if (len >= 4) print(" ", p[3], HEX);
					if (len >= 5) print(" ", p[4], HEX);
					if (len >= 6) print(" ", p[5], HEX);
					switch (subtype) {
						case 0: println(" - Header Functional Descriptor"); break;
						case 1: println(" - Call Management Functional"); break;
						case 2: println(" - Abstract Control Management"); break;
						case 4: println(" - Telephone Ringer"); break;
						case 6: println("  - union Functional"); break;
						default: println(" - ??? other"); break; 
					}
					// First pass ignore...
				} else if (type == 5) {
					// endpoint descriptor
					if (p[0] < 7) return false; // at least 7 bytes
					if (p[3] == 2) {  // First try ignore the first one which is interrupt...
						println("     Endpoint: ", p[2], HEX);
						switch (p[2] & 0xF0) {
						case 0x80:
							// IN endpoint
							if (rx_ep == 0) {
								rx_ep = p[2] & 0x0F;
								rx_size = p[4] | (p[5] << 8);
								println("      rx_size = ", rx_size);
							}
							break;
						case 0x00:
							// OUT endpoint
							if (tx_ep == 0) {
								tx_ep = p[2];
								tx_size = p[4] | (p[5] << 8);
								println("      tx_size = ", tx_size);
							}
							break;
						default:
							println("  invalid end point: ", p[2]);
							return false;
						}
					}
				} else {
					println("  Unknown type: ", type);
					return false; // unknown
				}
				p += len;
			}
			print("  exited loop rx:", rx_ep);
			println(", tx:", tx_ep);
			if (!rx_ep || !tx_ep) return false; 	// did not get our two end points
			if (!init_buffers(rx_size, tx_size)) return false;
			println("  rx buffer size:", rxsize);
			println("  tx buffer size:", txsize);
			rxpipe = new_Pipe(dev, 2, rx_ep & 15, 1, rx_size);
			if (!rxpipe) return false;
			txpipe = new_Pipe(dev, 2, tx_ep, 0, tx_size);
			if (!txpipe) {
				// TODO: free rxpipe
				return false;
			}
			sertype = CDCACM;
			rxpipe->callback_function = rx_callback;
			queue_Data_Transfer(rxpipe, rx1, (rx_size < 64)? rx_size : 64, this);
			rxstate = 1;
			if (rx_size > 128) {
				queue_Data_Transfer(rxpipe, rx2, rx_size, this);
				rxstate = 3;
			}
			txstate = 0;
			txpipe->callback_function = tx_callback;
			baudrate = 115200;
			// Wish I could just call Control to do the output... Maybe can defer until the user calls begin()
			// control requires that device is setup which is not until this call completes...
			println("Control - CDCACM DTR...");
			// Need to setup  the data the line coding data
			mk_setup(setup, 0x21, 0x22, 3, 0, 0);
			queue_Control_Transfer(dev, &setup, NULL, this);
			control_queued = true;
			pending_control = 0x0;	// Maybe don't need to do...
			return true;
		}

		// See if the vendor_id:product_id is in our list of products.
		sertype = UNKNOWN;
		for (uint8_t i = 0; i < (sizeof(pid_vid_mapping)/sizeof(pid_vid_mapping[0])); i++) {
			if ((dev->idVendor == pid_vid_mapping[i].idVendor) && (dev->idProduct == pid_vid_mapping[i].idProduct)) {
				sertype = pid_vid_mapping[i].sertype;
				break;
			}
		}  
		if (sertype == UNKNOWN) return false; 	// not one of ours

		// Lets try to locate the end points.  Code is common across these devices
		println("len = ", len);
		uint8_t count_end_points = descriptors[4];
		if (count_end_points < 2) return false; // not enough end points
		if (len < 23) return false;
		if (descriptors[0] != 9) return false; // length 9

		// Lets walk through end points and see if we 
		// can find an RX and TX bulk transfer end point.
		//Example vid=67B, pid=2303
		// 0  1  2  3  4  5  6  7  8  9 10  1  2  3  4  5  6  7  8  9 20  1  2  3  4  5  6  7  8  9
		//09 04 00 00 03 FF 00 00 00 07 05 81 03 0A 00 01 07 05 02 02 40 00 00 07 05 83 02 40 00 00 
		uint32_t rxep = 0;
		uint32_t txep = 0;
		uint16_t rx_size = 0;
		uint16_t tx_size = 0;
		uint32_t descriptor_index = 9; 
		while (count_end_points-- && ((rxep == 0) || txep == 0)) {
			if (descriptors[descriptor_index] != 7) return false; // length 7
			if (descriptors[descriptor_index+1] != 5) return false; // ep desc
			if ((descriptors[descriptor_index+3] == 2) 
				&& (descriptors[descriptor_index+4] <= 64)
				&& (descriptors[descriptor_index+5] == 0)) {
				// have a bulk EP size 
				if (descriptors[descriptor_index+2] & 0x80 ) {
					rxep = descriptors[descriptor_index+2];
					rx_size = descriptors[descriptor_index+4];
				} else {
					txep = descriptors[descriptor_index+2]; 
					tx_size = descriptors[descriptor_index+4];
				}
			}
			descriptor_index += 7;  // setup to look at next one...
		}
		// Try to verify the end points. 
		if (!check_rxtx_ep(rxep, txep)) return false;
		print("USBSerial, rxep=", rxep & 15);
		print("(", rx_size);
		print("), txep=", txep);
		print("(", tx_size);
		println(")");

		if (!init_buffers(rx_size, tx_size)) return false;
		println("  rx buffer size:", rxsize);
		println("  tx buffer size:", txsize);

		rxpipe = new_Pipe(dev, 2, rxep & 15, 1, rx_size);
		if (!rxpipe) return false;
		txpipe = new_Pipe(dev, 2, txep, 0, tx_size);
		if (!txpipe) {
			//free_Pipe(rxpipe);
			return false;
		}
		rxpipe->callback_function = rx_callback;
		queue_Data_Transfer(rxpipe, rx1, rx_size, this);
		rxstate = 1;
		txstate = 0;
		txpipe->callback_function = tx_callback;
		baudrate = 115200;

		// Now do specific setup per type
		switch (sertype) {
		//---------------------------------------------------------------------
		// FTDI
		case FTDI:
			{
				pending_control = 0x0F;
				mk_setup(setup, 0x40, 0, 0, 0, 0); // reset port
				queue_Control_Transfer(dev, &setup, NULL, this);
				control_queued = true;
				return true;
			}
		//------------------------------------------------------------------------
		// Prolific
		// TODO: Note: there are probably more vendor/product pairs.. Maybe should create table of them
		case PL2303: 
			{
				//  First attempt keep it simple... 
				println("PL2303: readRegister(0x04)");
				// Need to setup  the data the line coding data
				mk_setup(setup, 0xC0, 0x1, 0x8484, 0, 1);  
				queue_Control_Transfer(dev, &setup, setupdata, this); 
				control_queued = true;
				setup_state = 1; 	// We are at step one of setup... 
				pending_control = 0x3f;
				return true;
			}
		//------------------------------------------------------------------------
		// CH341
		case CH341:
			{
				println("CH341:  0xC0, 0x5f, 0, 0, 8");
				// Need to setup  the data the line coding data
				mk_setup(setup, 0xC0, 0x5f, 0, 0, sizeof(setupdata));  
				queue_Control_Transfer(dev, &setup, setupdata, this); 
				control_queued = true;
				setup_state = 1; 	// We are at step one of setup... 
				pending_control = 0x7f;	
				return true;
			}
		//------------------------------------------------------------------------
		// CP210X
		case CP210X:
			{
				println("CP210X:  0x41, 0x11, 0, 0, 0 - reset port");
				// Need to setup  the data the line coding data
				mk_setup(setup, 0x41, 0x11, 0, 0, 0);  
				queue_Control_Transfer(dev, &setup, NULL, this); 
				control_queued = true;
				setup_state = 1; 	// We are at step one of setup... 
				pending_control = 0xf;	
				return true;
			}
		//------------------------------------------------------------------------
		// PID:VID - not in our product list. 
		default:
			return false;
		}
	} else if (type != 1) return false;
	// TTYACM: <Composit device> 
	// 
	// We first tried to claim a simple ttyACM device like a teensy who is configured
	// only as Serial at the device level like what was done for midi
	//
	// However some devices are a compisit of multiple Interfaces, so see if this Interface
	// is of the CDC Interface class and 0 for SubClass and protocol
	// Todo: some of this can maybe be combined with the Whole device code above. 
	
	if (descriptors[0] != 9 || descriptors[1] != 4) return false; // interface descriptor
	if (descriptors[4] < 2) return false; 		// less than 2 end points
	if (descriptors[5] != 0xA) return false; // bInterfaceClass, 0xa = CDC data
	if (descriptors[6] != 0) return false; // bInterfaceSubClass
	if (descriptors[7] != 0) return false; // bInterfaceProtocol

	if (descriptors[9] != 7) return false; // length 7
	if (descriptors[10] != 5) return false; // ep desc
	uint32_t txep = descriptors[11];
	uint32_t txsize = descriptors[13];
	if (descriptors[12] != 2) return false; // bulk type
	if (descriptors[13] > 64) return false; // size 64 Max
	if (descriptors[14] != 0) return false;

	if (descriptors[16] != 7) return false; // length 7
	if (descriptors[17] != 5) return false; // ep desc
	uint32_t rxep = descriptors[18];
	uint32_t rxsize = descriptors[20];
	if (descriptors[19] != 2) return false; // bulk type
	if (descriptors[20] > 64) return false; // size 64 Max
	if (descriptors[21] != 0) return false;
	if (!check_rxtx_ep(rxep, txep)) return false;
	interface = descriptors[2];

	print("CDC, rxep=", rxep & 15);
	println(", txep=", txep);
	if (!init_buffers(rxsize, txsize)) return false;
	rxpipe = new_Pipe(dev, 2, rxep & 15, 1, rxsize);
	if (!rxpipe) return false;
	txpipe = new_Pipe(dev, 2, txep, 0, txsize);
	if (!txpipe) {
		// TODO: free rxpipe
		return false;
	}
	sertype = CDCACM;
	rxpipe->callback_function = rx_callback;
	queue_Data_Transfer(rxpipe, rx1, 64, this);
	rxstate = 1;
	if (rxsize > 128) {
		queue_Data_Transfer(rxpipe, rx2, 64, this);
		rxstate = 3;
	}
	txstate = 0;
	txpipe->callback_function = tx_callback;

	// See if we can do just the inteface...
	baudrate = 115200;
	println("Control - CDCACM LINE_CODING");
	setupdata[0] = 0;  // Setup baud rate 115200 - 0x1C200
	setupdata[1] = 0xc2;
	setupdata[2] = 0x1;
	setupdata[3] = 0;
    setupdata[4] = 0; // 0 - 1 stop bit, 1 - 1.5 stop bits, 2 - 2 stop bits
    setupdata[5] = 0; // 0 - None, 1 - Odd, 2 - Even, 3 - Mark, 4 - Space
    setupdata[6] = 8; // Data bits (5, 6, 7, 8 or 16)
	mk_setup(setup, 0x21, 0x20, 0, 0, 7);
	queue_Control_Transfer(dev, &setup, setupdata, this);
	pending_control = 0x04;	// Maybe don't need to do...
	control_queued = true;
	return true;
}

// check if two legal endpoints, 1 receive & 1 transmit
bool USBSerial::check_rxtx_ep(uint32_t &rxep, uint32_t &txep)
{
	if ((rxep & 0x0F) == 0) return false;
	if ((txep & 0x0F) == 0) return false;
	uint32_t rxdir = rxep & 0xF0;
	uint32_t txdir = txep & 0xF0;
	if (rxdir == 0x80 && txdir == 0x00) {
		return true;
	}
	if (rxdir == 0x00 && txdir == 0x80) {
		std::swap(rxep, txep);
		return true;
	}
	return false;
}

// initialize buffer sizes and pointers
bool USBSerial::init_buffers(uint32_t rsize, uint32_t tsize)
{
	// buffer must be able to hold 2 of each packet, plus buffer
	// space to hold RX and TX data. 
	if (sizeof(bigbuffer) < (rsize + tsize) * 3 + 2) return false;
	rx1 = (uint8_t *)bigbuffer;
	rx2 = rx1 + rsize;
	tx1 = rx2 + rsize;
	tx2 = tx1 + tsize;
	rxbuf = tx2 + tsize;
	// FIXME: this assume 50-50 split - not true when rsize != tsize
	rxsize = (sizeof(bigbuffer) - (rsize + tsize) * 2) / 2;
	txsize = rxsize;
	txbuf = rxbuf + rxsize;
	rxhead = 0;
	rxtail = 0;
	txhead = 0;
	txtail = 0;
	rxstate = 0;
	return true;
}

void USBSerial::disconnect()
{
}



void USBSerial::control(const Transfer_t *transfer)
{
	println("control callback (serial) ", pending_control, HEX);
	control_queued = false;

	// We will split this up by Serial type, maybe different functions? 

	//-------------------------------------------------------------------------
	// First FTDI
	if (sertype == FTDI) {
		if (pending_control & 1) {
			pending_control &= ~1;
			// set data format
			uint16_t ftdi_format = format_ & 0xf;	// This should give us the number of bits.

			// now lets extract the parity from our encoding
			ftdi_format |= (format_ & 0xe0) << 3;	// they encode bits 9-11

			// See if two stop bits
			if (format_ & 0x100) ftdi_format |= (0x2 << 11);

			mk_setup(setup, 0x40, 4, ftdi_format, 0, 0); // data format 8N1
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}
		// set baud rate
		if (pending_control & 2) {
			pending_control &= ~2;
			uint32_t baudval = 3000000 / baudrate;
			mk_setup(setup, 0x40, 3, baudval, 0, 0);
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}
		// configure flow control
		if (pending_control & 4) {
			pending_control &= ~4;
			mk_setup(setup, 0x40, 2, 0, 1, 0);
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true; 
			return;
		}
		// set DTR
		if (pending_control & 8) {
			pending_control &= ~8;
			mk_setup(setup, 0x40, 1, 0x0101, 0, 0);
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}
		// clear DTR
		if (pending_control & 0x80) {
			pending_control &= ~0x80;
			println("FTDI clear DTR");
			mk_setup(setup, 0x40, 1, 0x0100, 0, 0);
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}

	}

	//-------------------------------------------------------------------------
	// Now CDCACM
	if (sertype == CDCACM) {
		if (pending_control & 2) {
			pending_control &= ~2;
			// Should probably use data structure, but that may depend on byte ordering...
			setupdata[0] = (baudrate) & 0xff;  // Setup baud rate 115200 - 0x1C200
			setupdata[1] = (baudrate >> 8) & 0xff;
			setupdata[2] = (baudrate >> 16) & 0xff;
			setupdata[3] = (baudrate >> 24) & 0xff;
	        setupdata[4] = (format_ & 0x100)? 2 : 0; 	// 0 - 1 stop bit, 1 - 1.5 stop bits, 2 - 2 stop bits
	        setupdata[5] = (format_ & 0xe0) >> 5; 		// 0 - None, 1 - Odd, 2 - Even, 3 - Mark, 4 - Space
	        setupdata[6] = format_ & 0x1f;				// Data bits (5, 6, 7, 8 or 16)
	        print("CDCACM setup: ");
	        print_hexbytes(&setupdata, 7);
			mk_setup(setup, 0x21, 0x20, 0, 0, 7);
			queue_Control_Transfer(device, &setup, setupdata, this);
			control_queued = true;
			return;
		}
		// configure flow control
		if (pending_control & 4) {
			pending_control &= ~4;
			println("Control - 0x21,0x22, 0x3");
			// Need to setup  the data the line coding data
			mk_setup(setup, 0x21, 0x22, 3, 0, 0);
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}
		if (pending_control & 0x80) {
			pending_control &= ~0x80;
			println("Control - 0x21,0x22, 0x0 - clear DTR");
			// Need to setup  the data the line coding data
			mk_setup(setup, 0x21, 0x22, 0, 0, 0);
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}
	}

	//-------------------------------------------------------------------------
	// Now PL2303 - Which appears to be a little more complicated
	if (sertype == PL2303) {
		if (pending_control & 1) {
			// Still in larger setup state mode
			switch (setup_state) {
				case 1:
					println("PL2303: writeRegister(0x04, 0x00)");
					mk_setup(setup, 0x40, 1, 0x0404, 0, 0); // 
					queue_Control_Transfer(device, &setup, NULL, this);
					setup_state = 2; 
					control_queued = true;
					return;
				case 2:
					println("PL2303: readRegister(0x04)");
					mk_setup(setup, 0xC0, 0x1, 0x8484, 0, 1);  
					queue_Control_Transfer(device, &setup, setupdata, this); 
					control_queued = true;
					setup_state = 3; 
					return;
				case 3:
					println("PL2303: v1 = readRegister(0x03)");
					mk_setup(setup, 0xC0, 0x1, 0x8383, 0, 1);  
					queue_Control_Transfer(device, &setup, setupdata, this); 
					control_queued = true;
					setup_state = 4; 
					return;
				case 4:
					println("PL2303: readRegister(0x04)");
					// Do we need this value long term or we could just leave in setup data? 
					pl2303_v1 = setupdata[0];	// save the first bye of version
					mk_setup(setup, 0xC0, 0x1, 0x8484, 0, 1);  
					queue_Control_Transfer(device, &setup, setupdata, this); 
					control_queued = true;
					setup_state = 5; 
					return;
				case 5:
					println("PL2303: writeRegister(0x04, 0x01)");
					mk_setup(setup, 0x40, 1, 0x0404, 1, 0); // 
					queue_Control_Transfer(device, &setup, NULL, this);
					setup_state = 6; 
					control_queued = true;
					return;
				case 6:
					println("PL2303: readRegister(0x04)");
					mk_setup(setup, 0xC0, 0x1, 0x8484, 0, 1);  
					queue_Control_Transfer(device, &setup, setupdata, this); 
					control_queued = true;
					setup_state = 7; 
					return;
				case 7:
					println("PL2303: v2 = readRegister(0x03)");
					mk_setup(setup, 0xC0, 0x1, 0x8383, 0, 1);  
					queue_Control_Transfer(device, &setup, setupdata, this); 
					control_queued = true;
					setup_state = 8; 
					return;
				case 8:
					pl2303_v2 = setupdata[0];	// save the first bye of version
					print(" PL2303 Version ", pl2303_v1, HEX);
					println(":", pl2303_v2, HEX);
					println("PL2303: writeRegister(0, 1)");
					mk_setup(setup, 0x40, 1, 0, 1, 0); // 
					queue_Control_Transfer(device, &setup, NULL, this);
					setup_state = 9; 
					control_queued = true;
					return;
				case 9:
					println("PL2303: writeRegister(1, 0)");
					mk_setup(setup, 0x40, 1, 1, 0, 0); // 
					queue_Control_Transfer(device, &setup, NULL, this);
					setup_state = 10; 
					control_queued = true;
					return;
				case 10:
					println("PL2303: writeRegister(2, 44)");
					mk_setup(setup, 0x40, 1, 2, 0x44, 0); // 
					queue_Control_Transfer(device, &setup, NULL, this);
					setup_state = 11; 
					control_queued = true;
					return;
				case 11:
					println("PL2303: writeRegister(8, 0)");
					mk_setup(setup, 0x40, 1, 8, 0, 0); // 
					queue_Control_Transfer(device, &setup, NULL, this);
					setup_state = 12; 
					control_queued = true;
					return;
				case 12:
					println("PL2303: writeRegister(9, 0)");
					mk_setup(setup, 0x40, 1, 9, 0, 0); // 
					queue_Control_Transfer(device, &setup, NULL, this);
					setup_state = 13; 
					control_queued = true;
					return;
				case 13:
					println("PL2303: Read current Baud/control");
					mk_setup(setup, 0xA1, 0x21, 0, 0, 7);
					queue_Control_Transfer(device, &setup, setupdata, this);
					control_queued = true;
					break;
			}
			pending_control &= ~1;  // We are finally going to leave this list and join the rest
			if (control_queued) return;
		}

		// set baud rate
		if (pending_control & 2) {
			pending_control &= ~2;
			// See what the read returned earlier
			print("PL2303: Returned configuration data: ");
			print_hexbytes(setupdata, 7);

			// Should probably use data structure, but that may depend on byte ordering...
			setupdata[0] = (baudrate) & 0xff;  // Setup baud rate 115200 - 0x1C200
			setupdata[1] = (baudrate >> 8) & 0xff;
			setupdata[2] = (baudrate >> 16) & 0xff;
			setupdata[3] = (baudrate >> 24) & 0xff;
	        setupdata[4] = (format_ & 0x100)? 2 : 0; 	// 0 - 1 stop bit, 1 - 1.5 stop bits, 2 - 2 stop bits
	        setupdata[5] = (format_ & 0xe0) >> 5; 		// 0 - None, 1 - Odd, 2 - Even, 3 - Mark, 4 - Space
	        setupdata[6] = format_ & 0x1f;				// Data bits (5, 6, 7, 8 or 16)
	        print("PL2303: Set baud/control: ", baudrate, HEX);
	        print(" = ");
	        print_hexbytes(&setupdata, 7);
			mk_setup(setup, 0x21, 0x20, 0, 0, 7);
			queue_Control_Transfer(device, &setup, setupdata, this);
			control_queued = true;
			return;
		}
		if (pending_control & 4) {
			pending_control &= ~4;
			println("PL2303: writeRegister(0, 0)");
			mk_setup(setup, 0x40, 1, 0, 0, 0); // 
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return; 
		}
		if (pending_control & 8) {
			pending_control &= ~8;
			println("PL2303: Read current Baud/control");
			memset(setupdata, 0, sizeof(setupdata));	// clear it to see if we read it...
			mk_setup(setup, 0xA1, 0x21, 0, 0, 7);
			queue_Control_Transfer(device, &setup, setupdata, this);
			control_queued = true;
		}
		if (pending_control & 0x10) {
			pending_control &= ~0x10;
			print("PL2303: Returned configuration data: ");
			print_hexbytes(setupdata, 7);

			// This sets the control lines (0x1=DTR, 0x2=RTS)
			println("PL2303: 0x21, 0x22, 0x3");
			mk_setup(setup, 0x21, 0x22, 3, 0, 0); // 
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}
		if (pending_control & 0x20) {
			pending_control &= ~0x20;
			println("PL2303: 0x21, 0x22, 0x3");
			mk_setup(setup, 0x21, 0x22, 3, 0, 0); // 
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
		}
		if (pending_control & 0x80) {
			pending_control &= ~0x80;
			println("PL2303: 0x21, 0x22, 0x0");  // Clear DTR/RTS
			mk_setup(setup, 0x21, 0x22, 0, 0, 0); // 
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
		}
	}

	if (sertype == CH341) {
#if 0
		print("  Transfer: ");
		print_hexbytes(&transfer->setup, sizeof(setup_t));
		if (transfer->length) {
			print("  data: ");
			print_hexbytes(transfer->buffer, transfer->length);
		}
#endif
		if (pending_control & 1) {
			// Still in larger setup state mode
			switch (setup_state) {
				case 1:
					print("  Returned: ");
					print_hexbytes(transfer->buffer, transfer->length);
					println("CH341: 40, a1, 0, 0, 0");
					mk_setup(setup, 0x40, 0xa1, 0, 0, 0); // 
					queue_Control_Transfer(device, &setup, NULL, this);
					setup_state = 2; 
					control_queued = true;
					return;
				case 2:
					ch341_setBaud(0);	// send the first byte of the baud rate
					control_queued = true;
					setup_state = 3;
					return;
				case 3:
					ch341_setBaud(1);	// send the second byte of the baud rate
					control_queued = true;
					setup_state = 4;
					return;
				case 4:
					println("CH341: c0, 95, 2518, 0, 8");
					mk_setup(setup, 0xc0, 0x95, 0x2518, 0, sizeof(setup)); // 
					queue_Control_Transfer(device, &setup, setupdata, this);
					setup_state = 5; 
					control_queued = true;
					return;
				case 5:
					print("  Returned: ");
					print_hexbytes(transfer->buffer, transfer->length);
					println("CH341: 40, 0x9a, 0x2518, 0x0050, 0");
					mk_setup(setup, 0x40, 0x9a, 0x2518, 0x0050, 0); // 
					queue_Control_Transfer(device, &setup, NULL, this);
					setup_state = 6; 
					control_queued = true;
					return;
				case 6:
					println("CH341: c0, 95, 0x706, 0, 8 - get status");
					mk_setup(setup, 0xc0, 0x95, 0x706, 0, sizeof(setup)); // 
					queue_Control_Transfer(device, &setup, setupdata, this);
					setup_state = 7; 
					control_queued = true;
					return;
				case 7:
					print("  Returned: ");
					print_hexbytes(transfer->buffer, transfer->length);
					println("CH341: 40, 0xa1, 0x501f, 0xd90a, 0");
					mk_setup(setup, 0x40, 0xa1, 0x501f, 0xd90a, 0); // 
					queue_Control_Transfer(device, &setup, NULL, this);
					setup_state = 8; 
					control_queued = true;
					break;
			}
			pending_control &= ~1;  // We are finally going to leave this list and join the rest
			if (control_queued) return;
		}
		// set baud rate
		if (pending_control & 2) {
			pending_control &= ~2;
			ch341_setBaud(0);	// send the first byte of the baud rate
			control_queued = true;
			return;
		}
		if (pending_control & 4) {
			pending_control &= ~4;
			ch341_setBaud(1);	// send the first byte of the baud rate
			control_queued = true;
			return;
		}

		if (pending_control & 8) {
			pending_control &= ~8;
			uint16_t ch341_format;
			switch (format_) {
				default:
				// These values were observed when used on PC... Need to flush out others. 
				case USBHOST_SERIAL_8N1: ch341_format = 0xc3; break;
				case USBHOST_SERIAL_7E1: ch341_format = 0xda; break;
				case USBHOST_SERIAL_7O1: ch341_format = 0xca; break;
				case USBHOST_SERIAL_8N2: ch341_format = 0xc7; break;
			}
			println("CH341: 40, 0x9a, 0x2518: ", ch341_format, HEX);
			mk_setup(setup, 0x40, 0x9a, 0x2518, ch341_format, 0); // 
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}
		if (pending_control & 0x10) {
			pending_control &= ~0x10;
			// This is setting handshake need to figure out what...
			// 0x20=DTR, 0x40=RTS send ~ of values. 
			println("CH341: 0x40, 0xa4, 0xff9f, 0, 0 - Handshake");
			mk_setup(setup, 0x40, 0xa4, 0xff9f, 0, 0); // 
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}
		if (pending_control & 0x20) {
			pending_control &= ~0x20;
			// This is setting handshake need to figure out what...
			println("CH341: c0, 95, 0x706, 0, 8 - get status");
			mk_setup(setup, 0xc0, 0x95, 0x706, 0, sizeof(setup)); // 
			queue_Control_Transfer(device, &setup, setupdata, this);
			control_queued = true;
			return;
		}
		if (pending_control & 0x40) {
			pending_control &= ~0x40;
			print("  Returned: ");
			print_hexbytes(transfer->buffer, transfer->length);
			println("CH341: 0x40, 0x9a, 0x2727, 0, 0");
			mk_setup(setup, 0x40, 0x9a, 0x2727, 0, 0); // 
			queue_Control_Transfer(device, &setup, NULL, this);

			return;
		}

		if (pending_control & 0x80) {
			pending_control &= ~0x80;
			println("CH341: 0x40, 0xa4, 0xffff, 0, 0 - Handshake");
			mk_setup(setup, 0x40, 0xa4, 0xffff, 0, 0); // 
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}
	}
	//-------------------------------------------------------------------------
	// First CP210X
	if (sertype == CP210X) {
		if (pending_control & 1) {
			pending_control &= ~1;
			// set data format
			uint16_t cp210x_format = (format_ & 0xf) << 8;	// This should give us the number of bits.

			// now lets extract the parity from our encoding bits 5-7 and in theres 4-7
			cp210x_format |= (format_ & 0xe0) >> 1;	// they encode bits 9-11

			// See if two stop bits
			if (format_ & 0x100) cp210x_format |= 2;

			mk_setup(setup, 0x41, 3, cp210x_format, 0, 0); // data format 8N1
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}
		// set baud rate
		if (pending_control & 2) {
			pending_control &= ~2;
			setupdata[0] = (baudrate) & 0xff;  // Setup baud rate 115200 - 0x1C200
			setupdata[1] = (baudrate >> 8) & 0xff;
			setupdata[2] = (baudrate >> 16) & 0xff;
			setupdata[3] = (baudrate >> 24) & 0xff;
			mk_setup(setup, 0x40, 0x1e, 0, 0, 4);
			queue_Control_Transfer(device, &setup, setupdata, this);
			control_queued = true;
			return;
		}
		// configure flow control
		if (pending_control & 4) {
			pending_control &= ~4;
			memset(setupdata, 0, sizeof(setupdata));	// clear out the data
			setupdata[0] = 1; 	// Set dtr active? 
			mk_setup(setup, 0x41, 13, 0, 0, 0x10);
			queue_Control_Transfer(device, &setup, setupdata, this);
			control_queued = true; 
			return;
		}
		// set DTR
		if (pending_control & 8) {
			pending_control &= ~8;
			mk_setup(setup, 0x41, 7, 0x0101, 0, 0);
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}
		// clear DTR
		if (pending_control & 0x80) {
			pending_control &= ~0x80;
			println("CP210x clear DTR");
			mk_setup(setup, 0x40, 1, 0x0100, 0, 0);
			queue_Control_Transfer(device, &setup, NULL, this);
			control_queued = true;
			return;
		}

	}
}

#define CH341_BAUDBASE_FACTOR 1532620800
#define CH341_BAUDBASE_DIVMAX 3
void USBSerial::ch341_setBaud(uint8_t byte_index) {
	if (byte_index == 0) {
		uint32_t factor;
		uint16_t divisor;

		factor = (CH341_BAUDBASE_FACTOR / baudrate);
		divisor = CH341_BAUDBASE_DIVMAX;

		while ((factor > 0xfff0) && divisor) {
			factor >>= 3;
			divisor--;
		}

		factor = 0x10000 - factor;

		factor = (factor & 0xff00) | divisor;
		setupdata[0] = factor & 0xff;  // save away the low byte for 2nd message


		println("CH341: 40, 0x9a, 0x1312... (Baud word 0):", factor, HEX);
		mk_setup(setup, 0x40, 0x9a, 0x1312, factor, 0); // 
	} else {
		// Second packet use the byte we saved away during the calculation above
		println("CH341: 40, 0x9a, 0x0f2c... (Baud word 1):", setupdata[0], HEX);
		mk_setup(setup, 0x40, 0x9a, 0x0f2c, setupdata[0], 0); // 
	}
	queue_Control_Transfer(device, &setup, setupdata, this);
	control_queued = true;
}


/************************************************************/
//  Interrupt-based Data Movement
/************************************************************/

void USBSerial::rx_callback(const Transfer_t *transfer)
{
	if (!transfer->driver) return;
	((USBSerial *)(transfer->driver))->rx_data(transfer);
}

void USBSerial::tx_callback(const Transfer_t *transfer)
{
	if (!transfer->driver) return;
	((USBSerial *)(transfer->driver))->tx_data(transfer);
}


void USBSerial::rx_data(const Transfer_t *transfer)
{
	uint32_t len = transfer->length - ((transfer->qtd.token >> 16) & 0x7FFF);

	debugDigitalToggle(6);
	// first update rxstate bitmask, since buffer is no longer queued
	if (transfer->buffer == rx1) {
		rxstate &= 0xFE;
	} else if (transfer->buffer == rx2) {
		rxstate &= 0xFD;
	}
	// get start of data and actual length
	const uint8_t *p = (const uint8_t *)transfer->buffer;
	if (sertype == FTDI) {
		if (len >= 2) {
			p += 2;
			len -= 2;
		} else {
			len = 0;
		}
	}
	if (len > 0) {
		print("rx token: ", transfer->qtd.token, HEX);
		print(" transfer length: ", transfer->length, DEC);
		print(" len:", len, DEC);
		print(" - ", *p, HEX);
		println(" ", *(p+1), HEX);
		print("rx: ");
		print_hexbytes(p, len);
	}
	// Copy data from packet buffer to circular buffer.
	// Assume the buffer will always have space, since we
	// check before queuing the buffers
	uint32_t head = rxhead;
	uint32_t tail = rxtail;
	if (++head >= rxsize) head = 0;
	uint32_t avail;
	if (len > 0) {
		//print("head=", head);
		//print(", tail=", tail);
		avail = rxsize - head;
		//print(", avail=", avail);
		//println(", rxsize=", rxsize);
		if (avail > len) avail = len;
		memcpy(rxbuf + head, p, avail);
		if (len <= avail) {
			head += avail - 1;
			if (head >= rxsize) head = 0;
		} else {
			head = len - avail - 1;
			memcpy(rxbuf, p + avail, head + 1);
		}
		rxhead = head;
	}
	// TODO: can be this more efficient?  We know from above which
	// buffer is no longer queued, so possible skip most of this work?
	rx_queue_packets(head, tail);
}

// re-queue packet buffer(s) if possible
void USBSerial::rx_queue_packets(uint32_t head, uint32_t tail)
{
	uint32_t avail;
	if (head >= tail) {
		avail = rxsize - 1 - head + tail;
	} else {
		avail = tail - head - 1;
	}
	uint32_t packetsize = rx2 - rx1;
	if (avail >= packetsize) {
		if ((rxstate & 0x01) == 0) {
			queue_Data_Transfer(rxpipe, rx1, packetsize, this);
			rxstate |= 0x01;
		} else if ((rxstate & 0x02) == 0) {
			queue_Data_Transfer(rxpipe, rx2, packetsize, this);
			rxstate |= 0x02;
		}
		if ((rxstate & 0x03) != 0x03 && avail >= packetsize * 2) {
			if ((rxstate & 0x01) == 0) {
				queue_Data_Transfer(rxpipe, rx1, packetsize, this);
				rxstate |= 0x01;
			} else if ((rxstate & 0x02) == 0) {
				queue_Data_Transfer(rxpipe, rx2, packetsize, this);
				rxstate |= 0x02;
			}
		}
	}
}

void USBSerial::tx_data(const Transfer_t *transfer)
{
	uint32_t mask;
	uint8_t *p = (uint8_t *)transfer->buffer;
	debugDigitalWrite(5, HIGH);
	if (p == tx1) {
		println("tx1:");
		mask = 1;
		//txstate &= 0xFE;
	} else if (p == tx2) {
		println("tx2:");
		mask = 2;
		//txstate &= 0xFD;
	} else {
		debugDigitalWrite(5, LOW);
		return; // should never happen
	}
	// check how much more data remains in the transmit buffer
	uint32_t head = txhead;
	uint32_t tail = txtail;
	uint32_t count;
	if (head >= tail) {
		count = head - tail;
	} else {
		count = txsize + head - tail;
	}
	uint32_t packetsize = tx2 - tx1;
	// Only output full packets unless the flush bit was set.
	if ((count == 0) || ((count < packetsize) && ((txstate & 0x4) == 0) )) {
		// not enough data in buffer to fill a full packet
		txstate &= ~(mask | 4);	// turn off that transfer and make sure the flush bit is not set
		debugDigitalWrite(5, LOW);
		return;
	}
	// immediately transmit another full packet, if we have enough data
	if (count >= packetsize) count = packetsize;
	else txstate &= ~(mask | 4); // This packet will complete any outstanding flush

	println("TX:moar data!!!!");
	if (++tail >= txsize) tail = 0;
	uint32_t n = txsize - tail;
	if (n > count) n = count;
	memcpy(p, txbuf + tail, n);
	if (n >= count) {
		tail += n - 1;
		if (tail >= txsize) tail = 0;
	} else {
		uint32_t len = count - n;
		memcpy(p + n, txbuf, len);
		tail = len - 1;
	}
	txtail = tail;
	queue_Data_Transfer(txpipe, p, count, this);
	debugDigitalWrite(5, LOW);
}

void USBSerial::flush()
{
	print("USBSerial::flush");
 	if (txhead == txtail) {
 		println(" - Empty");
 		return;  // empty.
 	}
 	debugDigitalWrite(32, HIGH);
	NVIC_DISABLE_IRQ(IRQ_USBHS);
	txtimer.stop();  		// Stop longer timer.
	txtimer.start(100);		// Start a mimimal timeout
//	timer_event(nullptr);   // Try calling direct - fails to work 
	NVIC_ENABLE_IRQ(IRQ_USBHS);
	while (txstate & 3) ; // wait for all of the USB packets to be sent. 
	println(" completed");
 	debugDigitalWrite(32, LOW);
}



void USBSerial::timer_event(USBDriverTimer *whichTimer)
{
	debugDigitalWrite(7, HIGH);
	println("txtimer");
	uint32_t count;
	uint32_t head = txhead;
	uint32_t tail = txtail;
	if (head == tail) {
		println("  *** Empty ***");
		debugDigitalWrite(7, LOW);
		return; // nothing to transmit
	} else if (head > tail) {
		count = head - tail;
	} else {
		count = txsize + head - tail;
	}

	uint8_t *p;
	if ((txstate & 0x01) == 0) {
		p = tx1;
		txstate |= 0x01;
	} else if ((txstate & 0x02) == 0) {
		p = tx2;
		txstate |= 0x02;
	} else {
		txstate |= 4; 	// Tell the TX code to do flush code. 
		println(" *** No buffers ***");
		debugDigitalWrite(7, LOW);
		return; // no outgoing buffers available, try again later
	}

	uint32_t packetsize = tx2 - tx1;

	// Possible for remaining ? packet size and not have both? 
	if (count > packetsize) {
		txstate |= 4;	// One of the active transfers will handle the remaining parts
		count = packetsize;
	}

	if (++tail >= txsize) tail = 0;
	uint32_t n = txsize - tail;
	if (n > count) n = count;
	memcpy(p, txbuf + tail, n);
	if (n >= count) {
		tail += n - 1;
		if (tail >= txsize) tail = 0;
	} else {
		uint32_t len = count - n;
		memcpy(p + n, txbuf, len);
		tail = len - 1;
	}
	txtail = tail;
	print("  TX data (", count);
	print(") ");
	print_hexbytes(p, count);
	queue_Data_Transfer(txpipe, p, count, this);
	debugDigitalWrite(7, LOW);
}



/************************************************************/
//  User Functions - must disable USBHQ IRQ for EHCI access
/************************************************************/

void USBSerial::begin(uint32_t baud, uint32_t format)
{
	NVIC_DISABLE_IRQ(IRQ_USBHS);
	baudrate = baud;
	bool format_changed = format != format_;
	format_ = format; 
	switch (sertype) {
		default:
		case CDCACM: pending_control |= 0x6; break;
		case FTDI: pending_control |= (format_changed? 0xf : 0xe); break;	// Set BAUD, FLOW, DTR
		case PL2303: pending_control |= 0x1e; break;  // set more stuff...
		case CH341: pending_control |= 0x1e; break;
		case CP210X: pending_control |= 0xf; break;
	}
	if (!control_queued) control(NULL);
	NVIC_ENABLE_IRQ(IRQ_USBHS);
	// Wait until all packets have been queued before we return to caller. 
	while (pending_control) {
		yield();	// not sure if we want to yield or what? 
	}
}

void USBSerial::end(void)
{
	NVIC_DISABLE_IRQ(IRQ_USBHS);
	switch (sertype) {
		default:
		case CDCACM: pending_control |= 0x80; break;
		case FTDI: pending_control |= 0x80; break;	// clear DTR
		case PL2303: pending_control |= 0x80; break;
		case CH341: pending_control |= 0x80; break;
	}
	if (!control_queued) control(NULL);
	NVIC_ENABLE_IRQ(IRQ_USBHS);

	// Wait until all packets have been queued before we return to caller. 
	while (pending_control) {
		yield();	// not sure if we want to yield or what? 
	}
}

int USBSerial::available(void)
{
	if (!device) return 0;
	uint32_t head = rxhead;
	uint32_t tail = rxtail;
	if (head >= tail) return head - tail;
	return rxsize + head - tail;
}

int USBSerial::peek(void)
{
	if (!device) return -1;
	uint32_t head = rxhead;
	uint32_t tail = rxtail;
	if (head == tail) return -1;
	if (++tail >= rxsize) tail = 0;
	return rxbuf[tail];
}

int USBSerial::read(void)
{
	if (!device) return -1;
	uint32_t head = rxhead;
	uint32_t tail = rxtail;
	if (head == tail) return -1;
	if (++tail >= rxsize) tail = 0;
	int c = rxbuf[tail];
	rxtail = tail;
	if ((rxstate & 0x03) != 0x03) {
		NVIC_DISABLE_IRQ(IRQ_USBHS);
		rx_queue_packets(head, tail);
		NVIC_ENABLE_IRQ(IRQ_USBHS);
	}
	return c;
}

int USBSerial::availableForWrite()
{
	if (!device) return 0;
	uint32_t head = txhead;
	uint32_t tail = txtail;
	if (head >= tail) return txsize - 1 - head + tail;
	return tail - head - 1;
}

size_t USBSerial::write(uint8_t c)
{
	if (!device) return 0;
	uint32_t head = txhead;
	if (++head >= txsize) head = 0;
	while (txtail == head) {
		// wait...
	}
	txbuf[head] = c;
	txhead = head;
	//print("head=", head);
	//println(", tail=", txtail);

	// if full packet in buffer and tx packet ready, queue it
	NVIC_DISABLE_IRQ(IRQ_USBHS);
	uint32_t tail = txtail;
	if ((txstate & 0x03) != 0x03) {
		// at least one packet buffer is ready to transmit
		uint32_t count;
		if (head >= tail) {
			count = head - tail;
		} else {
			count = txsize + head - tail;
		}
		uint32_t packetsize = tx2 - tx1;
		if (count >= packetsize) {
			//println("txsize=", txsize);
			uint8_t *p;
			if ((txstate & 0x01) == 0) {
				p = tx1;
				txstate |= 0x01;
			} else /* if ((txstate & 0x02) == 0) */ {
				p = tx2;
				txstate |= 0x02;
			}
			// copy data to packet buffer
			if (++tail >= txsize) tail = 0;
			uint32_t n = txsize - tail;
			if (n > packetsize) n = packetsize;
			//print("memcpy, offset=", tail);
			//println(", len=", n);
			memcpy(p, txbuf + tail, n);
			if (n >= packetsize) {
				tail += n - 1;
				if (tail >= txsize) tail = 0;
			} else {
				//n = txsize - n;
				uint32_t len = packetsize - n;
				//println("memcpy, offset=0, len=", len);
				memcpy(p + n, txbuf, len);
				tail = len - 1;
			}
			txtail = tail;
			//println("queue tx packet, newtail=", tail);
			debugDigitalWrite(7, HIGH);
			queue_Data_Transfer(txpipe, p, packetsize, this);
			debugDigitalWrite(7, LOW);
			NVIC_ENABLE_IRQ(IRQ_USBHS);
			return 1;
		}
	}
	// otherwise, set a latency timer to later transmit partial packet
	txtimer.stop();
	txtimer.start(write_timeout_);
	NVIC_ENABLE_IRQ(IRQ_USBHS);
	return 1;
}