CDC.cpp

/*
  Copyright (c) 2015 Arduino LLC.  All right reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  See the GNU Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include <Arduino.h>
#include <Reset.h> // Needed for auto-reset with 1200bps port touch

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>

#ifdef CDC_ENABLED

#define CDC_SERIAL_BUFFER_SIZE	256

/* For information purpose only since RTS is not always handled by the terminal application */
#define CDC_LINESTATE_DTR		0x01 // Data Terminal Ready
#define CDC_LINESTATE_RTS		0x02 // Ready to Send

#define CDC_LINESTATE_READY		(CDC_LINESTATE_RTS | CDC_LINESTATE_DTR)

struct ring_buffer {
	uint8_t buffer[CDC_SERIAL_BUFFER_SIZE];
	volatile uint32_t head;
	volatile uint32_t tail;
	volatile bool full;
};
ring_buffer cdc_rx_buffer = {{0}, 0, 0, false};

typedef struct {
	uint32_t dwDTERate;
	uint8_t bCharFormat;
	uint8_t bParityType;
	uint8_t bDataBits;
	uint8_t lineState;
} LineInfo;

_Pragma("pack(1)")
static volatile LineInfo _usbLineInfo = {
	115200, // dWDTERate
	0x00,   // bCharFormat
	0x00,   // bParityType
	0x08,   // bDataBits
	0x00    // lineState
};

static volatile int32_t breakValue = -1;

static CDCDescriptor _cdcInterface = {
	D_IAD(0, 2, CDC_COMMUNICATION_INTERFACE_CLASS, CDC_ABSTRACT_CONTROL_MODEL, 0),

	// CDC communication interface
	D_INTERFACE(CDC_ACM_INTERFACE, 1, CDC_COMMUNICATION_INTERFACE_CLASS, CDC_ABSTRACT_CONTROL_MODEL, 0),
	D_CDCCS(CDC_HEADER, CDC_V1_10 & 0xFF, (CDC_V1_10>>8) & 0x0FF), // Header (1.10 bcd)

	D_CDCCS4(CDC_ABSTRACT_CONTROL_MANAGEMENT, 6), // SET_LINE_CODING, GET_LINE_CODING, SET_CONTROL_LINE_STATE supported
	D_CDCCS(CDC_UNION, CDC_ACM_INTERFACE, CDC_DATA_INTERFACE), // Communication interface is master, data interface is slave 0
	D_CDCCS(CDC_CALL_MANAGEMENT, 1, 1), // Device handles call management (not)
	D_ENDPOINT(USB_ENDPOINT_IN(CDC_ENDPOINT_ACM), USB_ENDPOINT_TYPE_INTERRUPT, 0x10, 0x10),

	// CDC data interface
	D_INTERFACE(CDC_DATA_INTERFACE, 2, CDC_DATA_INTERFACE_CLASS, 0, 0),
	D_ENDPOINT(USB_ENDPOINT_OUT(CDC_ENDPOINT_OUT), USB_ENDPOINT_TYPE_BULK, EPX_SIZE, 0),
	D_ENDPOINT(USB_ENDPOINT_IN (CDC_ENDPOINT_IN ), USB_ENDPOINT_TYPE_BULK, EPX_SIZE, 0)
};
_Pragma("pack()")

const void* _CDC_GetInterface(void)
{
	return &_cdcInterface;
}

uint32_t _CDC_GetInterfaceLength(void)
{
	return sizeof(_cdcInterface);
}

int CDC_GetInterface(uint8_t* interfaceNum)
{
	interfaceNum[0] += 2;	// uses 2
	return USBDevice.sendControl(&_cdcInterface,sizeof(_cdcInterface));
}

bool CDC_Setup(USBSetup& setup)
{
	uint8_t requestType = setup.bmRequestType;
	uint8_t r = setup.bRequest;

	if (requestType == REQUEST_DEVICETOHOST_CLASS_INTERFACE)
	{
		if (r == CDC_GET_LINE_CODING)
		{
			USBDevice.sendControl((void*)&_usbLineInfo, 7);
			return true;
		}
	}

	if (requestType == REQUEST_HOSTTODEVICE_CLASS_INTERFACE)
	{
		if (r == CDC_SET_LINE_CODING)
		{
			USBDevice.recvControl((void*)&_usbLineInfo, 7);
		}

		if (r == CDC_SET_CONTROL_LINE_STATE)
		{
			_usbLineInfo.lineState = setup.wValueL;
		}

		if (r == CDC_SET_LINE_CODING || r == CDC_SET_CONTROL_LINE_STATE)
		{
			// auto-reset into the bootloader is triggered when the port, already
			// open at 1200 bps, is closed. We check DTR state to determine if host 
			// port is open (bit 0 of lineState).
			if (_usbLineInfo.dwDTERate == 1200 && (_usbLineInfo.lineState & 0x01) == 0)
			{
				initiateReset(250);
			}
			else
			{
				cancelReset();
			}
			return false;
		}

		if (CDC_SEND_BREAK == r)
		{
			breakValue = ((uint16_t)setup.wValueH << 8) | setup.wValueL;
			return false;
		}
	}
	return false;
}

uint32_t _serialPeek = -1;
void Serial_::begin(uint32_t /* baud_count */)
{
	// uart config is ignored in USB-CDC
}

void Serial_::begin(uint32_t /* baud_count */, uint8_t /* config */)
{
	// uart config is ignored in USB-CDC
}

void Serial_::end(void)
{
}

void Serial_::accept(void)
{
	uint32_t ringBufferSpace = availableForStore();
	if (ringBufferSpace < EPX_SIZE) {
		// usb.recv will always try to receive up to EPX_SIZE bytes on the endpoint
		// make sure there is enough space, so that data is not lost
		return;
	}

	uint8_t buffer[EPX_SIZE];
	uint32_t len = usb.recv(CDC_ENDPOINT_OUT, &buffer, sizeof(buffer));

	uint8_t enableInterrupts = ((__get_PRIMASK() & 0x1) == 0);
	__disable_irq();

	ring_buffer *ringBuffer = &cdc_rx_buffer;
	uint32_t i = ringBuffer->head;

	// if we should be storing the received character into the location
	// just before the tail (meaning that the head would advance to the
	// current location of the tail), we're about to overflow the buffer
	// and so we don't write the character or advance the head.
	uint32_t k = 0;
	while (len > 0 && !ringBuffer->full) {
		len--;
		ringBuffer->buffer[i++] = buffer[k++];
		i %= CDC_SERIAL_BUFFER_SIZE;
		if (i == ringBuffer->tail)
			ringBuffer->full = true;
	}
	ringBuffer->head = i;
	if (enableInterrupts) {
		__enable_irq();
	}
}

int Serial_::available(void)
{
	ring_buffer *buffer = &cdc_rx_buffer;
	if (buffer->full) {
		return CDC_SERIAL_BUFFER_SIZE;
	}
	if (buffer->head == buffer->tail) {
		if (usb.available(CDC_ENDPOINT_OUT))
			accept();
	}
	return (uint32_t)(CDC_SERIAL_BUFFER_SIZE + buffer->head - buffer->tail) % CDC_SERIAL_BUFFER_SIZE;
}

int Serial_::peek(void)
{
	ring_buffer *buffer = &cdc_rx_buffer;
	if (buffer->head == buffer->tail && !buffer->full) {
		return -1;
	} else {
		return buffer->buffer[buffer->tail];
	}
}


// if the ringBuffer is empty: try to fill it
// if it's still empty: return -1
// else return the last char
// so the buffer is filled only when needed
int Serial_::read(void)
{
	ring_buffer *buffer = &cdc_rx_buffer;

	// if the head isn't ahead of the tail, we don't have any characters
	if (buffer->head == buffer->tail && !buffer->full)
	{
		if (usb.available(CDC_ENDPOINT_OUT))
			accept();
	}
	if (buffer->head == buffer->tail && !buffer->full)
	{
		return -1;
	}
	else
	{
		unsigned char c = buffer->buffer[buffer->tail];
		buffer->tail = (uint32_t)(buffer->tail + 1) % CDC_SERIAL_BUFFER_SIZE;
		buffer->full = false;

		return c;
	}
}

void Serial_::flush(void)
{
	usb.flush(CDC_ENDPOINT_IN);
}

size_t Serial_::write(const uint8_t *buffer, size_t size)
{
	/* only try to send bytes if the high-level CDC connection itself
	 is open (not just the pipe) - the OS should set lineState when the port
	 is opened and clear lineState when the port is closed.
	 bytes sent before the user opens the connection or after
	 the connection is closed are lost - just like with a UART. */

	// TODO - ZE - check behavior on different OSes and test what happens if an
	// open connection isn't broken cleanly (cable is yanked out, host dies
	// or locks up, or host virtual serial port hangs)
	if (_usbLineInfo.lineState > 0)  // Problem with Windows(R)
	{
		uint32_t r = usb.send(CDC_ENDPOINT_IN, buffer, size);

		if (r == 0) {
			return r;
		} else {
			setWriteError();
			return 0;
		}
	}
	setWriteError();
	return 0;
}

size_t Serial_::write(uint8_t c) {
	return write(&c, 1);
}

// This operator is a convenient way for a sketch to check whether the
// port has actually been configured and opened by the host (as opposed
// to just being connected to the host).  It can be used, for example, in
// setup() before printing to ensure that an application on the host is
// actually ready to receive and display the data.
// We add a short delay before returning to fix a bug observed by Federico
// where the port is configured (lineState != 0) but not quite opened.
Serial_::operator bool()
{
	// this is here to avoid spurious opening after upload
	if (millis() < 500)
		return false;

	bool result = false;

	if (_usbLineInfo.lineState > 0)
	{
		result = true;
	}

	delay(10);
	return result;
}

int32_t Serial_::readBreak() {
	uint8_t enableInterrupts = ((__get_PRIMASK() & 0x1) == 0);

	// disable interrupts,
	// to avoid clearing a breakValue that might occur 
	// while processing the current break value
	__disable_irq();

	int32_t ret = breakValue;

	breakValue = -1;

	if (enableInterrupts) {
		// re-enable the interrupts
		__enable_irq();
	}

	return ret;
}

unsigned long Serial_::baud() {
	return _usbLineInfo.dwDTERate;
}

uint8_t Serial_::stopbits() {
	return _usbLineInfo.bCharFormat;
}

uint8_t Serial_::paritytype() {
	return _usbLineInfo.bParityType;
}

uint8_t Serial_::numbits() {
	return _usbLineInfo.bDataBits;
}

bool Serial_::dtr() {
	return _usbLineInfo.lineState & 0x1;
}

bool Serial_::rts() {
	return _usbLineInfo.lineState & 0x2;
}

int Serial_::availableForStore(void) {
	ring_buffer *buffer = &cdc_rx_buffer;

	if (buffer->full)
		return 0;
	else if (buffer->head >= buffer->tail)
		return CDC_SERIAL_BUFFER_SIZE - 1 - buffer->head + buffer->tail;
	else
		return buffer->tail - buffer->head  - 1;
}

Serial_ SerialUSB(USBDevice);

#endif