Cours:LeonardoSerialUsb

Présentation de la bibliothèque

Nous allons utiliser du code du site pjrc.com : https://www.pjrc.com/teensy/usb_serial.html

Nous aurons besoin des 2 fichiers suivants :

Fichier : usb_serial.h

#ifndef usb_serial_h__
#define usb_serial_h__

#include <stdint.h>

// setup
void usb_init(void);			// initialize everything
uint8_t usb_configured(void);		// is the USB port configured

// receiving data
int16_t usb_serial_getchar(void);	// receive a character (-1 if timeout/error)
uint8_t usb_serial_available(void);	// number of bytes in receive buffer
void usb_serial_flush_input(void);	// discard any buffered input

// transmitting data
int8_t usb_serial_putchar(uint8_t c);	// transmit a character
int8_t usb_serial_putchar_nowait(uint8_t c);  // transmit a character, do not wait
int8_t usb_serial_write(const uint8_t *buffer, uint16_t size); // transmit a buffer
void usb_serial_flush_output(void);	// immediately transmit any buffered output

// serial parameters
uint32_t usb_serial_get_baud(void);	// get the baud rate
uint8_t usb_serial_get_stopbits(void);	// get the number of stop bits
uint8_t usb_serial_get_paritytype(void);// get the parity type
uint8_t usb_serial_get_numbits(void);	// get the number of data bits
uint8_t usb_serial_get_control(void);	// get the RTS and DTR signal state
int8_t usb_serial_set_control(uint8_t signals); // set DSR, DCD, RI, etc

// constants corresponding to the various serial parameters
#define USB_SERIAL_DTR			0x01
#define USB_SERIAL_RTS			0x02
#define USB_SERIAL_1_STOP		0
#define USB_SERIAL_1_5_STOP		1
#define USB_SERIAL_2_STOP		2
#define USB_SERIAL_PARITY_NONE		0
#define USB_SERIAL_PARITY_ODD		1
#define USB_SERIAL_PARITY_EVEN		2
#define USB_SERIAL_PARITY_MARK		3
#define USB_SERIAL_PARITY_SPACE		4
#define USB_SERIAL_DCD			0x01
#define USB_SERIAL_DSR			0x02
#define USB_SERIAL_BREAK		0x04
#define USB_SERIAL_RI			0x08
#define USB_SERIAL_FRAME_ERR		0x10
#define USB_SERIAL_PARITY_ERR		0x20
#define USB_SERIAL_OVERRUN_ERR		0x40

// This file does not include the HID debug functions, so these empty
// macros replace them with nothing, so users can compile code that
// has calls to these functions.
#define usb_debug_putchar(c)
#define usb_debug_flush_output()



// Everything below this point is only intended for usb_serial.c
#ifdef USB_SERIAL_PRIVATE_INCLUDE
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <avr/interrupt.h>

#define EP_TYPE_CONTROL			0x00
#define EP_TYPE_BULK_IN			0x81
#define EP_TYPE_BULK_OUT		0x80
#define EP_TYPE_INTERRUPT_IN		0xC1
#define EP_TYPE_INTERRUPT_OUT		0xC0
#define EP_TYPE_ISOCHRONOUS_IN		0x41
#define EP_TYPE_ISOCHRONOUS_OUT		0x40
#define EP_SINGLE_BUFFER		0x02
#define EP_DOUBLE_BUFFER		0x06
#define EP_SIZE(s)	((s) == 64 ? 0x30 :	\
			((s) == 32 ? 0x20 :	\
			((s) == 16 ? 0x10 :	\
			             0x00)))

#define MAX_ENDPOINT		4

#define LSB(n) (n & 255)
#define MSB(n) ((n >> 8) & 255)

#if defined(__AVR_AT90USB162__)
#define HW_CONFIG() 
#define PLL_CONFIG() (PLLCSR = ((1<<PLLE)|(1<<PLLP0)))
#define USB_CONFIG() (USBCON = (1<<USBE))
#define USB_FREEZE() (USBCON = ((1<<USBE)|(1<<FRZCLK)))
#elif defined(__AVR_ATmega32U4__)
#define HW_CONFIG() (UHWCON = 0x01)
#define PLL_CONFIG() (PLLCSR = 0x12)
#define USB_CONFIG() (USBCON = ((1<<USBE)|(1<<OTGPADE)))
#define USB_FREEZE() (USBCON = ((1<<USBE)|(1<<FRZCLK)))
#elif defined(__AVR_AT90USB646__)
#define HW_CONFIG() (UHWCON = 0x81)
#define PLL_CONFIG() (PLLCSR = 0x1A)
#define USB_CONFIG() (USBCON = ((1<<USBE)|(1<<OTGPADE)))
#define USB_FREEZE() (USBCON = ((1<<USBE)|(1<<FRZCLK)))
#elif defined(__AVR_AT90USB1286__)
#define HW_CONFIG() (UHWCON = 0x81)
#define PLL_CONFIG() (PLLCSR = 0x16)
#define USB_CONFIG() (USBCON = ((1<<USBE)|(1<<OTGPADE)))
#define USB_FREEZE() (USBCON = ((1<<USBE)|(1<<FRZCLK)))
#endif

// standard control endpoint request types
#define GET_STATUS			0
#define CLEAR_FEATURE			1
#define SET_FEATURE			3
#define SET_ADDRESS			5
#define GET_DESCRIPTOR			6
#define GET_CONFIGURATION		8
#define SET_CONFIGURATION		9
#define GET_INTERFACE			10
#define SET_INTERFACE			11
// HID (human interface device)
#define HID_GET_REPORT			1
#define HID_GET_PROTOCOL		3
#define HID_SET_REPORT			9
#define HID_SET_IDLE			10
#define HID_SET_PROTOCOL		11
// CDC (communication class device)
#define CDC_SET_LINE_CODING		0x20
#define CDC_GET_LINE_CODING		0x21
#define CDC_SET_CONTROL_LINE_STATE	0x22
#endif
#endif

Fichier : usb_serial.c

/* USB Serial Example for Teensy USB Development Board
 * http://www.pjrc.com/teensy/usb_serial.html
 * Copyright (c) 2008,2010,2011 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:
 * 
 * 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.
 */

// Version 1.0: Initial Release
// Version 1.1: support Teensy++
// Version 1.2: fixed usb_serial_available
// Version 1.3: added transmit bandwidth test
// Version 1.4: added usb_serial_write
// Version 1.5: add support for Teensy 2.0
// Version 1.6: fix zero length packet bug
// Version 1.7: fix usb_serial_set_control

#define USB_SERIAL_PRIVATE_INCLUDE
#include "usb_serial.h"


/**************************************************************************
 *
 *  Configurable Options
 *
 **************************************************************************/

// You can change these to give your code its own name.  On Windows,
// these are only used before an INF file (driver install) is loaded.
#define STR_MANUFACTURER	L"Your Name"
#define STR_PRODUCT		L"USB Serial"

// All USB serial devices are supposed to have a serial number
// (according to Microsoft).  On windows, a new COM port is created
// for every unique serial/vendor/product number combination.  If
// you program 2 identical boards with 2 different serial numbers
// and they are assigned COM7 and COM8, each will always get the
// same COM port number because Windows remembers serial numbers.
//
// On Mac OS-X, a device file is created automatically which
// incorperates the serial number, eg, /dev/cu-usbmodem12341
//
// Linux by default ignores the serial number, and creates device
// files named /dev/ttyACM0, /dev/ttyACM1... in the order connected.
// Udev rules (in /etc/udev/rules.d) can define persistent device
// names linked to this serial number, as well as permissions, owner
// and group settings.
#define STR_SERIAL_NUMBER	L"12345"

// Mac OS-X and Linux automatically load the correct drivers.  On
// Windows, even though the driver is supplied by Microsoft, an
// INF file is needed to load the driver.  These numbers need to
// match the INF file.
#define VENDOR_ID		0x16C0
#define PRODUCT_ID		0x047A

// When you write data, it goes into a USB endpoint buffer, which
// is transmitted to the PC when it becomes full, or after a timeout
// with no more writes.  Even if you write in exactly packet-size
// increments, this timeout is used to send a "zero length packet"
// that tells the PC no more data is expected and it should pass
// any buffered data to the application that may be waiting.  If
// you want data sent immediately, call usb_serial_flush_output().
#define TRANSMIT_FLUSH_TIMEOUT	5   /* in milliseconds */

// If the PC is connected but not "listening", this is the length
// of time before usb_serial_getchar() returns with an error.  This
// is roughly equivilant to a real UART simply transmitting the
// bits on a wire where nobody is listening, except you get an error
// code which you can ignore for serial-like discard of data, or
// use to know your data wasn't sent.
#define TRANSMIT_TIMEOUT	25   /* in milliseconds */

// USB devices are supposed to implment a halt feature, which is
// rarely (if ever) used.  If you comment this line out, the halt
// code will be removed, saving 116 bytes of space (gcc 4.3.0).
// This is not strictly USB compliant, but works with all major
// operating systems.
#define SUPPORT_ENDPOINT_HALT



/**************************************************************************
 *
 *  Endpoint Buffer Configuration
 *
 **************************************************************************/

// These buffer sizes are best for most applications, but perhaps if you
// want more buffering on some endpoint at the expense of others, this
// is where you can make such changes.  The AT90USB162 has only 176 bytes
// of DPRAM (USB buffers) and only endpoints 3 & 4 can double buffer.

#define ENDPOINT0_SIZE		16
#define CDC_ACM_ENDPOINT	2
#define CDC_RX_ENDPOINT		3
#define CDC_TX_ENDPOINT		4
#if defined(__AVR_AT90USB162__)
#define CDC_ACM_SIZE		16
#define CDC_ACM_BUFFER		EP_SINGLE_BUFFER
#define CDC_RX_SIZE		32
#define CDC_RX_BUFFER 		EP_DOUBLE_BUFFER
#define CDC_TX_SIZE		32
#define CDC_TX_BUFFER		EP_DOUBLE_BUFFER
#else
#define CDC_ACM_SIZE		16
#define CDC_ACM_BUFFER		EP_SINGLE_BUFFER
#define CDC_RX_SIZE		64
#define CDC_RX_BUFFER 		EP_DOUBLE_BUFFER
#define CDC_TX_SIZE		64
#define CDC_TX_BUFFER		EP_DOUBLE_BUFFER
#endif

static const uint8_t PROGMEM endpoint_config_table[] = {
	0,
	1, EP_TYPE_INTERRUPT_IN,  EP_SIZE(CDC_ACM_SIZE) | CDC_ACM_BUFFER,
	1, EP_TYPE_BULK_OUT,      EP_SIZE(CDC_RX_SIZE) | CDC_RX_BUFFER,
	1, EP_TYPE_BULK_IN,       EP_SIZE(CDC_TX_SIZE) | CDC_TX_BUFFER
};


/**************************************************************************
 *
 *  Descriptor Data
 *
 **************************************************************************/

// Descriptors are the data that your computer reads when it auto-detects
// this USB device (called "enumeration" in USB lingo).  The most commonly
// changed items are editable at the top of this file.  Changing things
// in here should only be done by those who've read chapter 9 of the USB
// spec and relevant portions of any USB class specifications!

const static uint8_t PROGMEM device_descriptor[] = {
	18,					// bLength
	1,					// bDescriptorType
	0x00, 0x02,				// bcdUSB
	2,					// bDeviceClass
	0,					// bDeviceSubClass
	0,					// bDeviceProtocol
	ENDPOINT0_SIZE,				// bMaxPacketSize0
	LSB(VENDOR_ID), MSB(VENDOR_ID),		// idVendor
	LSB(PRODUCT_ID), MSB(PRODUCT_ID),	// idProduct
	0x00, 0x01,				// bcdDevice
	1,					// iManufacturer
	2,					// iProduct
	3,					// iSerialNumber
	1					// bNumConfigurations
};

#define CONFIG1_DESC_SIZE (9+9+5+5+4+5+7+9+7+7)
const static uint8_t PROGMEM config1_descriptor[CONFIG1_DESC_SIZE] = {
	// configuration descriptor, USB spec 9.6.3, page 264-266, Table 9-10
	9, 					// bLength;
	2,					// bDescriptorType;
	LSB(CONFIG1_DESC_SIZE),			// wTotalLength
	MSB(CONFIG1_DESC_SIZE),
	2,					// bNumInterfaces
	1,					// bConfigurationValue
	0,					// iConfiguration
	0xC0,					// bmAttributes
	50,					// bMaxPower
	// interface descriptor, USB spec 9.6.5, page 267-269, Table 9-12
	9,					// bLength
	4,					// bDescriptorType
	0,					// bInterfaceNumber
	0,					// bAlternateSetting
	1,					// bNumEndpoints
	0x02,					// bInterfaceClass
	0x02,					// bInterfaceSubClass
	0x01,					// bInterfaceProtocol
	0,					// iInterface
	// CDC Header Functional Descriptor, CDC Spec 5.2.3.1, Table 26
	5,					// bFunctionLength
	0x24,					// bDescriptorType
	0x00,					// bDescriptorSubtype
	0x10, 0x01,				// bcdCDC
	// Call Management Functional Descriptor, CDC Spec 5.2.3.2, Table 27
	5,					// bFunctionLength
	0x24,					// bDescriptorType
	0x01,					// bDescriptorSubtype
	0x01,					// bmCapabilities
	1,					// bDataInterface
	// Abstract Control Management Functional Descriptor, CDC Spec 5.2.3.3, Table 28
	4,					// bFunctionLength
	0x24,					// bDescriptorType
	0x02,					// bDescriptorSubtype
	0x06,					// bmCapabilities
	// Union Functional Descriptor, CDC Spec 5.2.3.8, Table 33
	5,					// bFunctionLength
	0x24,					// bDescriptorType
	0x06,					// bDescriptorSubtype
	0,					// bMasterInterface
	1,					// bSlaveInterface0
	// endpoint descriptor, USB spec 9.6.6, page 269-271, Table 9-13
	7,					// bLength
	5,					// bDescriptorType
	CDC_ACM_ENDPOINT | 0x80,		// bEndpointAddress
	0x03,					// bmAttributes (0x03=intr)
	CDC_ACM_SIZE, 0,			// wMaxPacketSize
	64,					// bInterval
	// interface descriptor, USB spec 9.6.5, page 267-269, Table 9-12
	9,					// bLength
	4,					// bDescriptorType
	1,					// bInterfaceNumber
	0,					// bAlternateSetting
	2,					// bNumEndpoints
	0x0A,					// bInterfaceClass
	0x00,					// bInterfaceSubClass
	0x00,					// bInterfaceProtocol
	0,					// iInterface
	// endpoint descriptor, USB spec 9.6.6, page 269-271, Table 9-13
	7,					// bLength
	5,					// bDescriptorType
	CDC_RX_ENDPOINT,			// bEndpointAddress
	0x02,					// bmAttributes (0x02=bulk)
	CDC_RX_SIZE, 0,				// wMaxPacketSize
	0,					// bInterval
	// endpoint descriptor, USB spec 9.6.6, page 269-271, Table 9-13
	7,					// bLength
	5,					// bDescriptorType
	CDC_TX_ENDPOINT | 0x80,			// bEndpointAddress
	0x02,					// bmAttributes (0x02=bulk)
	CDC_TX_SIZE, 0,				// wMaxPacketSize
	0					// bInterval
};

// If you're desperate for a little extra code memory, these strings
// can be completely removed if iManufacturer, iProduct, iSerialNumber
// in the device desciptor are changed to zeros.
struct usb_string_descriptor_struct {
	uint8_t bLength;
	uint8_t bDescriptorType;
	int16_t wString[];
};
const static struct usb_string_descriptor_struct PROGMEM string0 = {
	4,
	3,
	{0x0409}
};
const static struct usb_string_descriptor_struct PROGMEM string1 = {
	sizeof(STR_MANUFACTURER),
	3,
	STR_MANUFACTURER
};
const static struct usb_string_descriptor_struct PROGMEM string2 = {
	sizeof(STR_PRODUCT),
	3,
	STR_PRODUCT
};
const static struct usb_string_descriptor_struct PROGMEM string3 = {
	sizeof(STR_SERIAL_NUMBER),
	3,
	STR_SERIAL_NUMBER
};

// This table defines which descriptor data is sent for each specific
// request from the host (in wValue and wIndex).
const static struct descriptor_list_struct {
	uint16_t	wValue;
	uint16_t	wIndex;
	const uint8_t	*addr;
	uint8_t		length;
} PROGMEM descriptor_list[] = {
	{0x0100, 0x0000, device_descriptor, sizeof(device_descriptor)},
	{0x0200, 0x0000, config1_descriptor, sizeof(config1_descriptor)},
	{0x0300, 0x0000, (const uint8_t *)&string0, 4},
	{0x0301, 0x0409, (const uint8_t *)&string1, sizeof(STR_MANUFACTURER)},
	{0x0302, 0x0409, (const uint8_t *)&string2, sizeof(STR_PRODUCT)},
	{0x0303, 0x0409, (const uint8_t *)&string3, sizeof(STR_SERIAL_NUMBER)}
};
#define NUM_DESC_LIST (sizeof(descriptor_list)/sizeof(struct descriptor_list_struct))


/**************************************************************************
 *
 *  Variables - these are the only non-stack RAM usage
 *
 **************************************************************************/

// zero when we are not configured, non-zero when enumerated
static volatile uint8_t usb_configuration=0;

// the time remaining before we transmit any partially full
// packet, or send a zero length packet.
static volatile uint8_t transmit_flush_timer=0;
static uint8_t transmit_previous_timeout=0;

// serial port settings (baud rate, control signals, etc) set
// by the PC.  These are ignored, but kept in RAM.
static uint8_t cdc_line_coding[7]={0x00, 0xE1, 0x00, 0x00, 0x00, 0x00, 0x08};
static uint8_t cdc_line_rtsdtr=0;


/**************************************************************************
 *
 *  Public Functions - these are the API intended for the user
 *
 **************************************************************************/

// initialize USB serial
void usb_init(void)
{
	HW_CONFIG();
        USB_FREEZE();				// enable USB
        PLL_CONFIG();				// config PLL, 16 MHz xtal
        while (!(PLLCSR & (1<<PLOCK))) ;	// wait for PLL lock
        USB_CONFIG();				// start USB clock
        UDCON = 0;				// enable attach resistor
	usb_configuration = 0;
	cdc_line_rtsdtr = 0;
        UDIEN = (1<<EORSTE)|(1<<SOFE);
	sei();
}

// return 0 if the USB is not configured, or the configuration
// number selected by the HOST
uint8_t usb_configured(void)
{
	return usb_configuration;
}

// get the next character, or -1 if nothing received
int16_t usb_serial_getchar(void)
{
	uint8_t c, intr_state;

	// interrupts are disabled so these functions can be
	// used from the main program or interrupt context,
	// even both in the same program!
	intr_state = SREG;
	cli();
	if (!usb_configuration) {
		SREG = intr_state;
		return -1;
	}
	UENUM = CDC_RX_ENDPOINT;
	retry:
	c = UEINTX;
	if (!(c & (1<<RWAL))) {
		// no data in buffer
		if (c & (1<<RXOUTI)) {
			UEINTX = 0x6B;
			goto retry;
		}	
		SREG = intr_state;
		return -1;
	}
	// take one byte out of the buffer
	c = UEDATX;
	// if buffer completely used, release it
	if (!(UEINTX & (1<<RWAL))) UEINTX = 0x6B;
	SREG = intr_state;
	return c;
}

// number of bytes available in the receive buffer
uint8_t usb_serial_available(void)
{
	uint8_t n=0, i, intr_state;

	intr_state = SREG;
	cli();
	if (usb_configuration) {
		UENUM = CDC_RX_ENDPOINT;
		n = UEBCLX;
		if (!n) {
			i = UEINTX;
			if (i & (1<<RXOUTI) && !(i & (1<<RWAL))) UEINTX = 0x6B;
		}
	}
	SREG = intr_state;
	return n;
}

// discard any buffered input
void usb_serial_flush_input(void)
{
	uint8_t intr_state;

	if (usb_configuration) {
		intr_state = SREG;
		cli();
		UENUM = CDC_RX_ENDPOINT;
		while ((UEINTX & (1<<RWAL))) {
			UEINTX = 0x6B; 
		}
		SREG = intr_state;
	}
}

// transmit a character.  0 returned on success, -1 on error
int8_t usb_serial_putchar(uint8_t c)
{
	uint8_t timeout, intr_state;

	// if we're not online (enumerated and configured), error
	if (!usb_configuration) return -1;
	// interrupts are disabled so these functions can be
	// used from the main program or interrupt context,
	// even both in the same program!
	intr_state = SREG;
	cli();
	UENUM = CDC_TX_ENDPOINT;
	// if we gave up due to timeout before, don't wait again
	if (transmit_previous_timeout) {
		if (!(UEINTX & (1<<RWAL))) {
			SREG = intr_state;
			return -1;
		}
		transmit_previous_timeout = 0;
	}
	// wait for the FIFO to be ready to accept data
	timeout = UDFNUML + TRANSMIT_TIMEOUT;
	while (1) {
		// are we ready to transmit?
		if (UEINTX & (1<<RWAL)) break;
		SREG = intr_state;
		// have we waited too long?  This happens if the user
		// is not running an application that is listening
		if (UDFNUML == timeout) {
			transmit_previous_timeout = 1;
			return -1;
		}
		// has the USB gone offline?
		if (!usb_configuration) return -1;
		// get ready to try checking again
		intr_state = SREG;
		cli();
		UENUM = CDC_TX_ENDPOINT;
	}
	// actually write the byte into the FIFO
	UEDATX = c;
	// if this completed a packet, transmit it now!
	if (!(UEINTX & (1<<RWAL))) UEINTX = 0x3A;
	transmit_flush_timer = TRANSMIT_FLUSH_TIMEOUT;
	SREG = intr_state;
	return 0;
}


// transmit a character, but do not wait if the buffer is full,
//   0 returned on success, -1 on buffer full or error 
int8_t usb_serial_putchar_nowait(uint8_t c)
{
	uint8_t intr_state;

	if (!usb_configuration) return -1;
	intr_state = SREG;
	cli();
	UENUM = CDC_TX_ENDPOINT;
	if (!(UEINTX & (1<<RWAL))) {
		// buffer is full
		SREG = intr_state;
		return -1;
	}
	// actually write the byte into the FIFO
	UEDATX = c;
		// if this completed a packet, transmit it now!
	if (!(UEINTX & (1<<RWAL))) UEINTX = 0x3A;
	transmit_flush_timer = TRANSMIT_FLUSH_TIMEOUT;
	SREG = intr_state;
	return 0;
}

// transmit a buffer.
//  0 returned on success, -1 on error
// This function is optimized for speed!  Each call takes approx 6.1 us overhead
// plus 0.25 us per byte.  12 Mbit/sec USB has 8.67 us per-packet overhead and
// takes 0.67 us per byte.  If called with 64 byte packet-size blocks, this function
// can transmit at full USB speed using 43% CPU time.  The maximum theoretical speed
// is 19 packets per USB frame, or 1216 kbytes/sec.  However, bulk endpoints have the
// lowest priority, so any other USB devices will likely reduce the speed.  Speed
// can also be limited by how quickly the PC-based software reads data, as the host
// controller in the PC will not allocate bandwitdh without a pending read request.
// (thanks to Victor Suarez for testing and feedback and initial code)

int8_t usb_serial_write(const uint8_t *buffer, uint16_t size)
{
	uint8_t timeout, intr_state, write_size;

	// if we're not online (enumerated and configured), error
	if (!usb_configuration) return -1;
	// interrupts are disabled so these functions can be
	// used from the main program or interrupt context,
	// even both in the same program!
	intr_state = SREG;
	cli();
	UENUM = CDC_TX_ENDPOINT;
	// if we gave up due to timeout before, don't wait again
	if (transmit_previous_timeout) {
		if (!(UEINTX & (1<<RWAL))) {
			SREG = intr_state;
			return -1;
		}
		transmit_previous_timeout = 0;
	}
	// each iteration of this loop transmits a packet
	while (size) {
		// wait for the FIFO to be ready to accept data
		timeout = UDFNUML + TRANSMIT_TIMEOUT;
		while (1) {
			// are we ready to transmit?
			if (UEINTX & (1<<RWAL)) break;
			SREG = intr_state;
			// have we waited too long?  This happens if the user
			// is not running an application that is listening
			if (UDFNUML == timeout) {
				transmit_previous_timeout = 1;
				return -1;
			}
			// has the USB gone offline?
			if (!usb_configuration) return -1;
			// get ready to try checking again
			intr_state = SREG;
			cli();
			UENUM = CDC_TX_ENDPOINT;
		}

		// compute how many bytes will fit into the next packet
		write_size = CDC_TX_SIZE - UEBCLX;
		if (write_size > size) write_size = size;
		size -= write_size;

		// write the packet
		switch (write_size) {
			#if (CDC_TX_SIZE == 64)
			case 64: UEDATX = *buffer++;
			case 63: UEDATX = *buffer++;
			case 62: UEDATX = *buffer++;
			case 61: UEDATX = *buffer++;
			case 60: UEDATX = *buffer++;
			case 59: UEDATX = *buffer++;
			case 58: UEDATX = *buffer++;
			case 57: UEDATX = *buffer++;
			case 56: UEDATX = *buffer++;
			case 55: UEDATX = *buffer++;
			case 54: UEDATX = *buffer++;
			case 53: UEDATX = *buffer++;
			case 52: UEDATX = *buffer++;
			case 51: UEDATX = *buffer++;
			case 50: UEDATX = *buffer++;
			case 49: UEDATX = *buffer++;
			case 48: UEDATX = *buffer++;
			case 47: UEDATX = *buffer++;
			case 46: UEDATX = *buffer++;
			case 45: UEDATX = *buffer++;
			case 44: UEDATX = *buffer++;
			case 43: UEDATX = *buffer++;
			case 42: UEDATX = *buffer++;
			case 41: UEDATX = *buffer++;
			case 40: UEDATX = *buffer++;
			case 39: UEDATX = *buffer++;
			case 38: UEDATX = *buffer++;
			case 37: UEDATX = *buffer++;
			case 36: UEDATX = *buffer++;
			case 35: UEDATX = *buffer++;
			case 34: UEDATX = *buffer++;
			case 33: UEDATX = *buffer++;
			#endif
			#if (CDC_TX_SIZE >= 32)
			case 32: UEDATX = *buffer++;
			case 31: UEDATX = *buffer++;
			case 30: UEDATX = *buffer++;
			case 29: UEDATX = *buffer++;
			case 28: UEDATX = *buffer++;
			case 27: UEDATX = *buffer++;
			case 26: UEDATX = *buffer++;
			case 25: UEDATX = *buffer++;
			case 24: UEDATX = *buffer++;
			case 23: UEDATX = *buffer++;
			case 22: UEDATX = *buffer++;
			case 21: UEDATX = *buffer++;
			case 20: UEDATX = *buffer++;
			case 19: UEDATX = *buffer++;
			case 18: UEDATX = *buffer++;
			case 17: UEDATX = *buffer++;
			#endif
			#if (CDC_TX_SIZE >= 16)
			case 16: UEDATX = *buffer++;
			case 15: UEDATX = *buffer++;
			case 14: UEDATX = *buffer++;
			case 13: UEDATX = *buffer++;
			case 12: UEDATX = *buffer++;
			case 11: UEDATX = *buffer++;
			case 10: UEDATX = *buffer++;
			case  9: UEDATX = *buffer++;
			#endif
			case  8: UEDATX = *buffer++;
			case  7: UEDATX = *buffer++;
			case  6: UEDATX = *buffer++;
			case  5: UEDATX = *buffer++;
			case  4: UEDATX = *buffer++;
			case  3: UEDATX = *buffer++;
			case  2: UEDATX = *buffer++;
			default:
			case  1: UEDATX = *buffer++;
			case  0: break;
		}
		// if this completed a packet, transmit it now!
		if (!(UEINTX & (1<<RWAL))) UEINTX = 0x3A;
		transmit_flush_timer = TRANSMIT_FLUSH_TIMEOUT;
		SREG = intr_state;
	}
	return 0;
}


// immediately transmit any buffered output.
// This doesn't actually transmit the data - that is impossible!
// USB devices only transmit when the host allows, so the best
// we can do is release the FIFO buffer for when the host wants it
void usb_serial_flush_output(void)
{
	uint8_t intr_state;

	intr_state = SREG;
	cli();
	if (transmit_flush_timer) {
		UENUM = CDC_TX_ENDPOINT;
		UEINTX = 0x3A;
		transmit_flush_timer = 0;
	}
	SREG = intr_state;
}

// functions to read the various async serial settings.  These
// aren't actually used by USB at all (communication is always
// at full USB speed), but they are set by the host so we can
// set them properly if we're converting the USB to a real serial
// communication
uint32_t usb_serial_get_baud(void)
{
	return *(uint32_t *)cdc_line_coding;
}
uint8_t usb_serial_get_stopbits(void)
{
	return cdc_line_coding[4];
}
uint8_t usb_serial_get_paritytype(void)
{
	return cdc_line_coding[5];
}
uint8_t usb_serial_get_numbits(void)
{
	return cdc_line_coding[6];
}
uint8_t usb_serial_get_control(void)
{
	return cdc_line_rtsdtr;
}
// write the control signals, DCD, DSR, RI, etc
// There is no CTS signal.  If software on the host has transmitted
// data to you but you haven't been calling the getchar function,
// it remains buffered (either here or on the host) and can not be
// lost because you weren't listening at the right time, like it
// would in real serial communication.
int8_t usb_serial_set_control(uint8_t signals)
{
	uint8_t intr_state;

	intr_state = SREG;
	cli();
	if (!usb_configuration) {
		// we're not enumerated/configured
		SREG = intr_state;
		return -1;
	}

	UENUM = CDC_ACM_ENDPOINT;
	if (!(UEINTX & (1<<RWAL))) {
		// unable to write
		// TODO; should this try to abort the previously
		// buffered message??
		SREG = intr_state;
		return -1;
	}
	UEDATX = 0xA1;
	UEDATX = 0x20;
	UEDATX = 0;
	UEDATX = 0;
	UEDATX = 0; // 0 seems to work nicely.  what if this is 1??
	UEDATX = 0;
	UEDATX = 1;
	UEDATX = 0;
	UEDATX = signals;
	UEINTX = 0x3A;
	SREG = intr_state;
	return 0;
}



/**************************************************************************
 *
 *  Private Functions - not intended for general user consumption....
 *
 **************************************************************************/


// USB Device Interrupt - handle all device-level events
// the transmit buffer flushing is triggered by the start of frame
//
ISR(USB_GEN_vect)
{
	uint8_t intbits, t;

        intbits = UDINT;
        UDINT = 0;
        if (intbits & (1<<EORSTI)) {
		UENUM = 0;
		UECONX = 1;
		UECFG0X = EP_TYPE_CONTROL;
		UECFG1X = EP_SIZE(ENDPOINT0_SIZE) | EP_SINGLE_BUFFER;
		UEIENX = (1<<RXSTPE);
		usb_configuration = 0;
		cdc_line_rtsdtr = 0;
        }
	if (intbits & (1<<SOFI)) {
		if (usb_configuration) {
			t = transmit_flush_timer;
			if (t) {
				transmit_flush_timer = --t;
				if (!t) {
					UENUM = CDC_TX_ENDPOINT;
					UEINTX = 0x3A;
				}
			}
		}
	}
}


// Misc functions to wait for ready and send/receive packets
static inline void usb_wait_in_ready(void)
{
	while (!(UEINTX & (1<<TXINI))) ;
}
static inline void usb_send_in(void)
{
	UEINTX = ~(1<<TXINI);
}
static inline void usb_wait_receive_out(void)
{
	while (!(UEINTX & (1<<RXOUTI))) ;
}
static inline void usb_ack_out(void)
{
	UEINTX = ~(1<<RXOUTI);
}



// USB Endpoint Interrupt - endpoint 0 is handled here.  The
// other endpoints are manipulated by the user-callable
// functions, and the start-of-frame interrupt.
//
ISR(USB_COM_vect)
{
        uint8_t intbits;
	const uint8_t *list;
        const uint8_t *cfg;
	uint8_t i, n, len, en;
	uint8_t *p;
	uint8_t bmRequestType;
	uint8_t bRequest;
	uint16_t wValue;
	uint16_t wIndex;
	uint16_t wLength;
	uint16_t desc_val;
	const uint8_t *desc_addr;
	uint8_t	desc_length;

        UENUM = 0;
        intbits = UEINTX;
        if (intbits & (1<<RXSTPI)) {
                bmRequestType = UEDATX;
                bRequest = UEDATX;
                wValue = UEDATX;
                wValue |= (UEDATX << 8);
                wIndex = UEDATX;
                wIndex |= (UEDATX << 8);
                wLength = UEDATX;
                wLength |= (UEDATX << 8);
                UEINTX = ~((1<<RXSTPI) | (1<<RXOUTI) | (1<<TXINI));
                if (bRequest == GET_DESCRIPTOR) {
			list = (const uint8_t *)descriptor_list;
			for (i=0; ; i++) {
				if (i >= NUM_DESC_LIST) {
					UECONX = (1<<STALLRQ)|(1<<EPEN);  //stall
					return;
				}
				desc_val = pgm_read_word(list);
				if (desc_val != wValue) {
					list += sizeof(struct descriptor_list_struct);
					continue;
				}
				list += 2;
				desc_val = pgm_read_word(list);
				if (desc_val != wIndex) {
					list += sizeof(struct descriptor_list_struct)-2;
					continue;
				}
				list += 2;
				desc_addr = (const uint8_t *)pgm_read_word(list);
				list += 2;
				desc_length = pgm_read_byte(list);
				break;
			}
			len = (wLength < 256) ? wLength : 255;
			if (len > desc_length) len = desc_length;
			do {
				// wait for host ready for IN packet
				do {
					i = UEINTX;
				} while (!(i & ((1<<TXINI)|(1<<RXOUTI))));
				if (i & (1<<RXOUTI)) return;	// abort
				// send IN packet
				n = len < ENDPOINT0_SIZE ? len : ENDPOINT0_SIZE;
				for (i = n; i; i--) {
					UEDATX = pgm_read_byte(desc_addr++);
				}
				len -= n;
				usb_send_in();
			} while (len || n == ENDPOINT0_SIZE);
			return;
                }
		if (bRequest == SET_ADDRESS) {
			usb_send_in();
			usb_wait_in_ready();
			UDADDR = wValue | (1<<ADDEN);
			return;
		}
		if (bRequest == SET_CONFIGURATION && bmRequestType == 0) {
			usb_configuration = wValue;
			cdc_line_rtsdtr = 0;
			transmit_flush_timer = 0;
			usb_send_in();
			cfg = endpoint_config_table;
			for (i=1; i<5; i++) {
				UENUM = i;
				en = pgm_read_byte(cfg++);
				UECONX = en;
				if (en) {
					UECFG0X = pgm_read_byte(cfg++);
					UECFG1X = pgm_read_byte(cfg++);
				}
			}
        		UERST = 0x1E;
        		UERST = 0;
			return;
		}
		if (bRequest == GET_CONFIGURATION && bmRequestType == 0x80) {
			usb_wait_in_ready();
			UEDATX = usb_configuration;
			usb_send_in();
			return;
		}
		if (bRequest == CDC_GET_LINE_CODING && bmRequestType == 0xA1) {
			usb_wait_in_ready();
			p = cdc_line_coding;
			for (i=0; i<7; i++) {
				UEDATX = *p++;
			}
			usb_send_in();
			return;
		}
		if (bRequest == CDC_SET_LINE_CODING && bmRequestType == 0x21) {
			usb_wait_receive_out();
			p = cdc_line_coding;
			for (i=0; i<7; i++) {
				*p++ = UEDATX;
			}
			usb_ack_out();
			usb_send_in();
			return;
		}
		if (bRequest == CDC_SET_CONTROL_LINE_STATE && bmRequestType == 0x21) {
			cdc_line_rtsdtr = wValue;
			usb_wait_in_ready();
			usb_send_in();
			return;
		}
		if (bRequest == GET_STATUS) {
			usb_wait_in_ready();
			i = 0;
			#ifdef SUPPORT_ENDPOINT_HALT
			if (bmRequestType == 0x82) {
				UENUM = wIndex;
				if (UECONX & (1<<STALLRQ)) i = 1;
				UENUM = 0;
			}
			#endif
			UEDATX = i;
			UEDATX = 0;
			usb_send_in();
			return;
		}
		#ifdef SUPPORT_ENDPOINT_HALT
		if ((bRequest == CLEAR_FEATURE || bRequest == SET_FEATURE)
		  && bmRequestType == 0x02 && wValue == 0) {
			i = wIndex & 0x7F;
			if (i >= 1 && i <= MAX_ENDPOINT) {
				usb_send_in();
				UENUM = i;
				if (bRequest == SET_FEATURE) {
					UECONX = (1<<STALLRQ)|(1<<EPEN);
				} else {
					UECONX = (1<<STALLRQC)|(1<<RSTDT)|(1<<EPEN);
					UERST = (1 << i);
					UERST = 0;
				}
				return;
			}
		}
		#endif
        }
	UECONX = (1<<STALLRQ) | (1<<EPEN);	// stall
}

Et un exemple pour essayer

Avec ces deux fichiers, vous disposez d'un exemple présenté dans la boîte déroulante ci-dessous. Même s'il est fait pour une carte Teensy, vous pouvez facilement l'utiliser avec une carte Arduino Leonardo. Ces deux cartes disposent du processeur AVR ATMega 32U4 qui possède une partie matérielle pour faire fonctionner l'USB.

Fichier : exemple.c

/* Simple example for Teensy USB Development Board
 * http://www.pjrc.com/teensy/
 * Copyright (c) 2008 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:
 * 
 * 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.
 */

#include <avr/io.h>
#include <avr/pgmspace.h>
#include <stdint.h>
#include <util/delay.h>
#include "usb_serial.h"

#define LED_CONFIG	(DDRD |= (1<<6))
#define LED_ON		(PORTD |= (1<<6))
#define LED_OFF		(PORTD &= ~(1<<6))
#define CPU_PRESCALE(n) (CLKPR = 0x80, CLKPR = (n))

void send_str(const char *s);
uint8_t recv_str(char *buf, uint8_t size);
void parse_and_execute_command(const char *buf, uint8_t num);

#if 0
// Very simple character echo test
int main(void)
{
	CPU_PRESCALE(0);
	usb_init();
	while (1) {
		int n = usb_serial_getchar();
		if (n >= 0) usb_serial_putchar(n);
	}
}

#else

// Basic command interpreter for controlling port pins
int main(void)
{
	char buf[32];
	uint8_t n;

	// set for 16 MHz clock, and turn on the LED
	CPU_PRESCALE(0);
	LED_CONFIG;
	LED_ON;

	// initialize the USB, and then wait for the host
	// to set configuration.  If the Teensy is powered
	// without a PC connected to the USB port, this 
	// will wait forever.
	usb_init();
	while (!usb_configured()) /* wait */ ;
	_delay_ms(1000);

	while (1) {
		// wait for the user to run their terminal emulator program
		// which sets DTR to indicate it is ready to receive.
		while (!(usb_serial_get_control() & USB_SERIAL_DTR)) /* wait */ ;

		// discard anything that was received prior.  Sometimes the
		// operating system or other software will send a modem
		// "AT command", which can still be buffered.
		usb_serial_flush_input();

		// print a nice welcome message
		send_str(PSTR("\r\nTeensy USB Serial Example, "
			"Simple Pin Control Shell\r\n\r\n"
			"Example Commands\r\n"
			"  B0?   Read Port B, pin 0\r\n"
			"  C2=0  Write Port C, pin 1 LOW\r\n"
			"  D6=1  Write Port D, pin 6 HIGH  (D6 is LED pin)\r\n\r\n"));

		// and then listen for commands and process them
		while (1) {
			send_str(PSTR("> "));
			n = recv_str(buf, sizeof(buf));
			if (n == 255) break;
			send_str(PSTR("\r\n"));
			parse_and_execute_command(buf, n);
		}
	}
}
#endif

// Send a string to the USB serial port.  The string must be in
// flash memory, using PSTR
//
void send_str(const char *s)
{
	char c;
	while (1) {
		c = pgm_read_byte(s++);
		if (!c) break;
		usb_serial_putchar(c);
	}
}

// Receive a string from the USB serial port.  The string is stored
// in the buffer and this function will not exceed the buffer size.
// A carriage return or newline completes the string, and is not
// stored into the buffer.
// The return value is the number of characters received, or 255 if
// the virtual serial connection was closed while waiting.
//
uint8_t recv_str(char *buf, uint8_t size)
{
	int16_t r;
	uint8_t count=0;

	while (count < size) {
		r = usb_serial_getchar();
		if (r != -1) {
			if (r == '\r' || r == '\n') return count;
			if (r >= ' ' && r <= '~') {
				*buf++ = r;
				usb_serial_putchar(r);
				count++;
			}
		} else {
			if (!usb_configured() ||
			  !(usb_serial_get_control() & USB_SERIAL_DTR)) {
				// user no longer connected
				return 255;
			}
			// just a normal timeout, keep waiting
		}
	}
	return count;
}

// parse a user command and execute it, or print an error message
//
void parse_and_execute_command(const char *buf, uint8_t num)
{
	uint8_t port, pin, val;

	if (num < 3) {
		send_str(PSTR("unrecognized format, 3 chars min req'd\r\n"));
		return;
	}
	// first character is the port letter
	if (buf[0] >= 'A' && buf[0] <= 'F') {
		port = buf[0] - 'A';
	} else if (buf[0] >= 'a' && buf[0] <= 'f') {
		port = buf[0] - 'a';
	} else {
		send_str(PSTR("Unknown port \""));
		usb_serial_putchar(buf[0]);
		send_str(PSTR("\", must be A - F\r\n"));
		return;
	}
	// second character is the pin number
	if (buf[1] >= '0' && buf[1] <= '7') {
		pin = buf[1] - '0';
	} else {
		send_str(PSTR("Unknown pin \""));
		usb_serial_putchar(buf[0]);
		send_str(PSTR("\", must be 0 to 7\r\n"));
		return;
	}
	// if the third character is a question mark, read the pin
	if (buf[2] == '?') {
		// make the pin an input
		*(uint8_t *)(0x21 + port * 3) &= ~(1 << pin);
		// read the pin
		val = *(uint8_t *)(0x20 + port * 3) & (1 << pin);
		usb_serial_putchar(val ? '1' : '0');
		send_str(PSTR("\r\n"));
		return;
	}
	// if the third character is an equals sign, write the pin
	if (num >= 4 && buf[2] == '=') {
		if (buf[3] == '0') {
			// make the pin an output
			*(uint8_t *)(0x21 + port * 3) |= (1 << pin);
			// drive it low
			*(uint8_t *)(0x22 + port * 3) &= ~(1 << pin);
			return;
		} else if (buf[3] == '1') {
			// make the pin an output
			*(uint8_t *)(0x21 + port * 3) |= (1 << pin);
			// drive it high
			*(uint8_t *)(0x22 + port * 3) |= (1 << pin);
			return;
		} else {
			send_str(PSTR("Unknown value \""));
			usb_serial_putchar(buf[3]);
			send_str(PSTR("\", must be 0 or 1\r\n"));
			return;
		}
	}
	// otherwise, error message
	send_str(PSTR("Unknown command \""));
	usb_serial_putchar(buf[0]);
	send_str(PSTR("\", must be ? or =\r\n"));
}

Compiler le programme d'exemple et essayez-le. Celui-ci doit être compilé avec avr-gcc et non pas avr-g++. Cela signifie qu'il sera difficile de l'utiliser avec l'environnement Arduino mais pourra être testé avec Eclipse.

Ce programme réalise un mini terminal série avec comme écran d'accueil :

Teensy USB Serial Example, Simple Pin Control Shell

Example Commands
  B0?   Read Port B, pin 0
  C2=0  Write Port C, pin 1 LOW
  D6=1  Write Port D, pin 6 HIGH  (D6 is LED pin)

Sur la carte Arduino Leonardo la célèbre LED 13 est câblée sur le bit 7 du PORTC. Ainsi l'envoi de la commande C7=0 vous éteindra cette LED 13 tandis que C7=1 l'allumera....

Voir aussi

• Bibliothèque LUFA pour Arduino
• MEAM.Design : ATmega32u4 : USB Communications
• Github associé au lien ci-dessus
• Wikibook en anglais
• USB in a Nutshell Chapter 1
• USB maide simple Part 1