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////////////////////////////////////////////////////////////////////////////////

//

// Filename:    uartsim.h

//

// Project:     wbuart32, a full featured UART with simulator

//

// Purpose:     To forward a Verilator simulated UART link over a TCP/IP pipe.

//

//      This file provides the description of the interface between the UARTSIM

//      and the rest of the world.  See below for more detailed descriptions.

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

////////////////////////////////////////////////////////////////////////////////

//

// Copyright (C) 2015-2017, Gisselquist Technology, LLC

//

// This program is free software (firmware): you can redistribute it and/or

// modify it under the terms of  the GNU General Public License as published

// by the Free Software Foundation, either version 3 of the License, or (at

// your option) any later version.

//

// This program is distributed in the hope that it will be useful, but WITHOUT

// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or

// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

// for more details.

//

// You should have received a copy of the GNU General Public License along

// with this program.  (It's in the $(ROOT)/doc directory.  Run make with no

// target there if the PDF file isn't present.)  If not, see

// <http://www.gnu.org/licenses/> for a copy.

//

// License:     GPL, v3, as defined and found on www.gnu.org,

//              http://www.gnu.org/licenses/gpl.html

//

//

////////////////////////////////////////////////////////////////////////////////

//

//

#ifndef UARTSIM_H

#define UARTSIM_H

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <poll.h>

#include <unistd.h>

#include <arpa/inet.h>

#include <signal.h>

#define TXIDLE  0

#define TXDATA  1

#define RXIDLE  0

#define RXDATA  1

class   UARTSIM {

        // The file descriptors:

        //      m_skt   is the socket/port we are listening on

        //      m_conrd is the file descriptor to read from

        //      m_conwr is the file descriptor to write to

        int     m_skt, m_conrd, m_conwr;

        //

        // The m_setup register is the 29'bit control register used within

        // the core.

        unsigned m_setup;

        // And the pieces of the setup register broken out.

        int     m_nparity, m_fixdp, m_evenp, m_nbits, m_nstop, m_baud_counts;

        // UART state

        int     m_rx_baudcounter, m_rx_state, m_rx_busy,

                m_rx_changectr, m_last_tx;

        int     m_tx_baudcounter, m_tx_state, m_tx_busy;

        unsigned        m_rx_data, m_tx_data;

        // setup_listener is an attempt to encapsulate all of the network

        // related setup stuff.

        void    setup_listener(const int port);

        // nettick() gets called if we are connected to a network, and

        int     nettick(const int i_tx);

        // fdtick() if we are not.

        int     fdtick(const int i_tx);

        // We'll use the file descriptor for the listener socket to determine

        // whether we are connected to the network or not.  If not connected

        // to the network, then we assume m_conrd and m_conwr refer to 

        // your more traditional file descriptors, and use them as such.

        int     tick(const int i_tx) {

                if (m_skt >= 0)

                        return nettick(i_tx);

                else

                        return fdtick(i_tx);

        }

public:

        //

        // The UARTSIM constructor takes one argument: the port on the

        // localhost to listen in on.  Once started, connections may be made

        // to this port to get the output from the port.

        UARTSIM(const int port);

        // kill() closes any active connection and the socket.  Once killed,

        // no further output will be sent to the port.

        void    kill(void);

        // setup() busts out the bits from isetup to the various internal

        // parameters.  It is ideally only called between bits at appropriate

        // transition intervals. 

        void    setup(unsigned isetup);

        // The operator() function is called on every tick.  The input is the

        // the output txuart transmit wire from the device.  The output is to

        // be connected to the the rxuart receive wire into the device.  This

        // makes hookup and operation very simple.

        //

        // This is the most appropriate simulation entry function if the 

        // setup register will never change.

        //

        int     operator()(int i_tx) {

                return tick(i_tx); }

        // If there is a possibility that the core might change the UART setup,

        // then it makes sense to include that current setup when calling the

        // tick operator.

        int     operator()(int i_tx, unsigned isetup) {

                setup(isetup); return tick(i_tx); }

};

#endif