/**
 *  file       TxDuino.h
 *  date:      Oct 27, 2009
 *  brief:
 *
 *  detail:
 */
 
#ifndef CTXDUINO_H_
#define CTXDUINO_H_
 
 
#include <vector>
#include <string>
 
#include "types.h"
 
 
namespace txduino
{
 
 
/**
 *  brief  operating system dependendant implementation structure
 */
struct STxDuinoImpl;
 
/**
 *  brief Class encapsulating the interface / API for communicating with one
 *  TxDuino device. The TxDuino sends a standard RC PPM signal encoding
 *  commands for up to 8 PWM channels (servos, engine controllers).
 *
 *  The magnitude of each channel is divided into 250 discrete segments.
 *  Exactly how those segments are interpreted by the actuators is determined
 *  by the configuration of this object.
 *
 *  note: channels are zero indexed
 *
 *  todo   add a constructor that accepts a csv file with the saturations and
 *          neutral points that can be generated from the test program
 */
class CTxDuino
{
    private:
        STxDuinoImpl*   m_osInfo;   /// pointer to os-dependant implementation
        std::string     m_devName;  /// system device name,
                                    /// i.e. "\.COM2", "/dev/tty2"
 
        u8          m_chan      [9];    /// value for each channel [0,250]
        u8          m_neutral   [8];    /// the "center" for each actuator
        u8          m_minsat    [8];    /// the minimum value for each channel
        u8          m_maxsat    [8];    /// the maximum value for each channel
 
 
    public:
        /**
         *  brief  Constructs a new TxDuino object serving as an interface
         *          into on particular TxDuino device.
         *  param  strDevice   device string, i.e. "\.COM2", "/dev/tty2"
         */
        CTxDuino( std::string strDevice );
 
 
        /**
         *  brief  cleans up OS resources reserved for this serial connection
         */
        virtual ~CTxDuino();
 
 
        /**
         *  brief  sends the current channel definitions to the device
         */
        void send();
 
 
        /**
         *  brief  sets the value of an actuator as a percent of it's viable
         *          range.
         *  param  chan        the channel to set
         *  param  percent     -100% < percent < 100%; value to set channel to
         */
        void setPercent( s32 chan, f64 percent );
 
 
        /**
         *  brief  returns the percent value the indicated actuator is set to,
         *          note: if the neutral point is equal to one of the saturation
         *          points this value may be unreliable
         *  param  chan        the channel to get
         *  return percent value of actuator on indicated channel
         */
        f64 getPercent( s32 chan );
 
 
        /**
         *  brief  sets the raw value of the actuator pulse width
         *  param  chan        the channel to set
         *  param  value      0 < value < 250; value to set channel to
         */
        void setRaw( s32 chan, u8 value );
 
 
        /**
         *  brief  returns the raw value the indicated actuator is set to
         *  param  chan        the channel to get
         *  return a value between 0 and 250 indicated the pulse length for
         *          that actuator (multiply by 4us and add 700us to get the
         *          actual pulse length)
         */
        u8 getRaw( s32 chan );
 
 
 
 
        /**
         *  brief  sets the raw value of the actuator pulse width corresponding
         *          to a neutral state of that actuator
         *  param  chan        the channel to set
         *  param  value      0 < value < 250; value to set channel to
         */
        void setNeutral( s32 chan, u8 value );
 
 
        /**
         *  brief  returns the raw value corresponding to a neutral state of
         *          the indicated actuator
         *  param  chan        the channel to get
         *  return a value between 0 and 250 indicated the pulse length for
         *          that actuator (multiply by 4us and add 700us to get the
         *          actual pulse length)
         */
        u8 getNeutral( s32 chan );
 
 
 
 
        /**
         *  brief  sets the raw value of the actuator pulse width corresponding
         *          to the minimum state of the indicated actuator
         *  param  chan        the channel to set
         *  param  value      0 < value < 250; value to set channel to
         */
        void setMinSat( s32 chan, u8 value );
 
 
        /**
         *  brief  returns the raw value corresponding to a minimum state of
         *          the indicated actuator
         *  param  chan        the channel to get
         *  return a value between 0 and 250 indicated the pulse length for
         *          that actuator (multiply by 4us and add 700us to get the
         *          actual pulse length)
         */
        u8 getMinSat( s32 chan );
 
 
 
 
        /**
         *  brief  sets the raw value of the actuator pulse width corresponding
         *          to the maximum state of the indicated actuator
         *  param  chan        the channel to set
         *  param  value      0 < value < 250; value to set channel to
         */
        void setMaxSat( s32 chan, u8 value );
 
 
        /**
         *  brief  returns the raw value corresponding to a maximum state of
         *          the indicated actuator
         *  param  chan        the channel to get
         *  return a value between 0 and 250 indicated the pulse length for
         *          that actuator (multiply by 4us and add 700us to get the
         *          actual pulse length)
         */
        u8 getMaxSat( s32 chan );
 
 
        /**
         *  brief  return the device name that was used to connect to this
         *          txduino
         */
        std::string getName();
 
};
 
}
 
#endif /* CTXDUINO_H_ */

/**
 *  file       CTxDuino.cpp
 *  date:      Oct 27, 2009
 *  brief:
 *
 *  detail:
 */
 
#include "CTxDuino.h"
#include "compile.h"
 
#include <iostream>
#include <iomanip>
#include <sstream>
#include <cmath>
 
#include "IllegalArgumentException.h"
#include "IOException.h"
 
#ifdef TXD_MINGW
#include <windows.h>
#endif
 
namespace txduino
{
 
 
 
#ifdef TXD_MINGW
struct STxDuinoImpl
{
    HANDLE hComPort;    /// handle to the opened COM device
};
#endif
 
 
#ifdef TXD_LINUX
struct STxDuinoImpl
{
    FILE hSerialFile;
};
#endif
 
 
 
 
 
 
/**
 *  The initial state of the individual actuators is initialized as follows
 *
 *  verbatim
 *      minimum saturation: 0
 *                 neutral: 125
 *      maximum saturation: 250
 *                   value: 125
 *  endverbatim
 *
 *  Note that this is probably not appropriate for your system. Many of the
 *  servos that we've used have minimum saturations around 10 and maximum
 *  saturations around 240. Use the actuator test program to determine what
 *  these values should be.
 */
CTxDuino::CTxDuino( std::string strDevice )
{
    using std::cout;
    using std::endl;
    using std::stringstream;
 
    // intiialize all the arrays
    for( int i=0; i < 8; i++ )
    {
        m_chan      [i] = 125;
        m_minsat    [i] = 0;
        m_maxsat    [i] = 250;
        m_neutral   [i] = 125;
    }
 
    // stop byte
    m_chan[8]   = 0xFF;
 
    // initialize the OS dependant information
    m_osInfo    = new STxDuinoImpl();
 
 
/* ----------------------------------------------------------------------------
 * Windows Specific Implementation:
 * ---------------------------------------------------------------------------*/
 
#ifdef TXD_MINGW
    // open the file using the windows API
    m_osInfo->hComPort  =
    CreateFile( strDevice.c_str(),          // file name
        GENERIC_READ | GENERIC_WRITE,       // access mode: read and write
        FILE_SHARE_READ|FILE_SHARE_WRITE,   // (sharing)
        NULL,                               // (security) 0: none
        OPEN_EXISTING,                      // (creation) i.e. don't make it
        0,                                  // (overlapped operation)
        NULL);                              // no template file
 
    // check to make sure the file open succeeded
    if( m_osInfo->hComPort == INVALID_HANDLE_VALUE )
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid Device Name: " << strDevice;
        throw IllegalArgumentException(message.str());
    }
 
    // get the current settings on the com port
    DCB dcb;
    GetCommState( m_osInfo->hComPort, &dcb );
 
    // change the settings, the TxDuino uses a BAUD rate of 9600
    dcb.fBinary     =   1;
    dcb.BaudRate    =   CBR_9600;
    dcb.Parity      =   NOPARITY;
    dcb.ByteSize    =   8;
    dcb.StopBits    =   ONESTOPBIT;
 
    // set the new settings for the port
    SetCommState( m_osInfo->hComPort, &dcb );
#endif
 
 
}
 
 
 
CTxDuino::~CTxDuino()
{
 
/* ----------------------------------------------------------------------------
 * Windows Specific Implementation:
 * ---------------------------------------------------------------------------*/
 
#ifdef TXD_MINGW
    // close the device if it's open
    if( m_osInfo->hComPort != INVALID_HANDLE_VALUE )
        CloseHandle( m_osInfo->hComPort );
#endif
 
delete m_osInfo;
 
}
 
 
 
void CTxDuino::send()
{
    using std::stringstream;
 
 
    // ensure that the last byte of the packet is the stop byte
    m_chan[8] = 0xFF;
 
 
/* ----------------------------------------------------------------------------
 * Windows Specific Implementation:
 * ---------------------------------------------------------------------------*/
 
#ifdef TXD_MINGW
    DWORD bytesWritten;
 
    BOOL retVal =
    WriteFile(  m_osInfo->hComPort, // output handle
                m_chan,             // buffer of bytes to send
                9,                  // number of bytes to send from buffer
                &bytesWritten,      // pointer to a word that receives number of
                                    // bytes written
                NULL);              // pointer to an OVERLAPPED struct
 
    if( bytesWritten != 9 )
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Bytes written to device less than expected: "
                << bytesWritten << ", expecting 9";
        throw IOException(message.str());
    }
 
    if( retVal == 0 )
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Writing to device failed; error code: " << GetLastError();
        throw IOException(message.str());
    }
#endif
 
}
 
 
 
/**
 *  If the percent is positive, the raw value is calculated as follows
 *
 *  verbatim
 *      raw = neutral + (max - neutral) * percent
 *  endverbatim
 *
 *  if the percent is negative, the raw value is calculated as follows
 *
 *  verbatim
 *      raw = neutral - (neutral - min) * percent
 *  endverbatim
 */
void CTxDuino::setPercent( s32 chan, f64 percent )
{
    using std::stringstream;
 
    if(chan < 0 || chan > 7)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid channel number: " << chan << HERE
                << "valid channels are 0-7";
    }
 
    if(percent > 0)
    {
        m_chan[chan] = (u8) (m_neutral[chan] +
                    ( m_maxsat[chan] - m_neutral[chan]) * percent );
    }
 
    else
    {
        m_chan[chan] = (u8) (m_neutral[chan] -
                    ( m_minsat[chan] - m_neutral[chan]) * percent );
    }
}
 
 
 
/**
 *  If the value is strictly less than the neutral value then the percent value
 *  is calculated by
 *
 *  verbatim
 *      percent = -( neutral - value ) / (neutral - min);
 *  endverbatim
 *
 *  If the value is strictly greater than the neutral value then the percent
 *  value is calculated by
 *
 *  verbatim
 *      percent = ( value - neutral ) / (max - neutral);
 *  endverbatim
 *
 *  If the value is equal to the neutral value then the percent value is zero.
 */
f64 CTxDuino::getPercent( s32 chan )
{
    using std::stringstream;
 
    if(chan < 0 || chan > 7)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid channel number: " << chan << HERE
                << "valid channels are 0-7";
    }
 
    if( m_chan[chan] < m_neutral[chan] )
    {
        return (double)(-(m_neutral[chan] - m_chan[chan])) /
                    (m_neutral[chan] - m_minsat[chan]);
    }
 
    else if( m_chan[chan] > m_neutral[chan] )
    {
        return (double)(m_chan[chan] - m_neutral[chan]) /
                    (m_maxsat[chan] - m_neutral[chan]);
    }
 
    else
    {
        return 0.0;
    }
}
 
 
 
void CTxDuino::setRaw( s32 chan, u8 value )
{
    using std::stringstream;
 
    if(chan < 0 || chan > 7)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid channel number: " << chan << HERE
                << "valid channels are 0-7";
    }
 
    if(value > 250)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid value: " << value << HERE
                << "valid channels are 0-250";
    }
 
    m_chan[chan] = value;
}
 
 
 
u8 CTxDuino::getRaw( s32 chan )
{
    using std::stringstream;
 
    if(chan < 0 || chan > 7)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid channel number: " << chan << HERE
                << "valid channels are 0-7";
    }
 
    return m_chan[chan];
}
 
 
 
void CTxDuino::setNeutral( s32 chan, u8 value )
{
    using std::stringstream;
 
    if(chan < 0 || chan > 7)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid channel number: " << chan << HERE
                << "valid channels are 0-7";
    }
 
    if(value > 250)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid value: " << value << HERE
                << "valid channels are 0-250";
    }
 
    m_neutral[chan] = value;
}
 
 
 
u8 CTxDuino::getNeutral( s32 chan )
{
    using std::stringstream;
 
    if(chan < 0 || chan > 7)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid channel number: " << chan << HERE
                << "valid channels are 0-7";
    }
 
    return m_neutral[chan];
}
 
 
 
void CTxDuino::setMinSat( s32 chan, u8 value )
{
    using std::stringstream;
 
    if(chan < 0 || chan > 7)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid channel number: " << chan << HERE
                << "valid channels are 0-7";
    }
 
    if(value > 250)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid value: " << value << HERE
                << "valid channels are 0-250";
    }
 
    m_minsat[chan] = value;
}
 
 
 
u8 CTxDuino::getMinSat( s32 chan )
{
    using std::stringstream;
 
    if(chan < 0 || chan > 7)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid channel number: " << chan << HERE
                << "valid channels are 0-7";
    }
 
    return m_minsat[chan];
}
 
 
 
void CTxDuino::setMaxSat( s32 chan, u8 value )
{
    using std::stringstream;
 
    if(chan < 0 || chan > 7)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid channel number: " << chan << HERE
                << "valid channels are 0-7";
    }
 
    if(value > 250)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid value: " << value << HERE
                << "valid channels are 0-250";
    }
 
    m_maxsat[chan] = value;
}
 
 
 
u8 CTxDuino::getMaxSat( s32 chan )
{
    using std::stringstream;
 
    if(chan < 0 || chan > 7)
    {
        stringstream message( stringstream::in | stringstream::out );
        message << "Invalid channel number: " << chan << HERE
                << "valid channels are 0-7";
    }
 
    return m_maxsat[chan];
}
 
 
 
std::string CTxDuino::getName()
{
    return m_devName;
}
 
 
 
 
 
 
}

/**
 * 	file		serialTest.cpp
 *  date:      Oct 27, 2009
 *  brief:
 *
 *  detail:
 *  This is a simple test program that demonstrates how to connect to and
 *  write commands to the arduino transmitter interface using windows.
 *
 *  the TxDuino is an interface into the futaba FP-TP-FM transmitter module,
 *  which accepts an RC PPM input. This signal contains a maximum of 8
 *  servo channels.
 */
 
#include <iostream>
#include <iomanip>
#include <cmath>
 
#include "CTxDuino.h"
#include "constants.h"
 
using namespace std;
using namespace txduino;
 
int main( int argc, char** argv )
{
    // check to ensure that the command line included a device to open
    if( argc < 2 )
    {
        cout << "Usage: serialTest.exe [Device Name]n"
                "   where [Device Name] is the name of the COM port file onn "
                "   windows (i.e. \\.\COM8), or the name of the serialn "
                "   device on *nix (i.e. /dev/tty8)n" << endl;
 
        return -1;
    }
 
    // grab a pointer to the device to open
    char*       strDevName = argv[1];
 
    // create the txduino device
    CTxDuino tx(strDevName);
 
    // send a sinusoidal input on all channels (except for channel 3, which is
    // usually the throttle) for 10 seconds
    for(int i=0; i < 1000; i++)
    {
        for(int j=0; j < 8; j++)
            tx.setRaw(j, (unsigned char)
                            (125.0 + 75.0 * sin( 2.0 * PI * i / 100.0 )) );
 
        tx.setRaw(2, 0);
 
        for(int j=0; j < 8; j++)
            cout << setw(3) << (int)tx.getRaw(j) << " | ";
        cout << endl;
 
        tx.send();
 
#ifdef TXD_MIGNW
        Sleep(1);
#endif
 
#ifdef TXD_LINUX
        usleep(0.001);
#endif
    }
 
 
    return 0;
}

        1   2   3   4   5
        .   .   .   .   .
 
     left side
     #1 PPM
     #2 V+
     #3 RF check
     #4 ground
     #5 RF out
     right side

 int inByte = 0;         // incoming serial byte
 
 //define the Timer1 overflow interrupt service routine
 ISR(TIMER1_OVF_vect) 
 {
    // print out the current value of the timer control register B which
    // contains the timer prescale value, set when the serial BAUD rate 
    // is defined
    Serial.print("Timer1: ");
    Serial.print(TCCR1B, HEX);
    Serial.print("rn");
 }
 
 
 void setup()
 {
   // set Timer1 to operate in "normal" mode
   TCCR1A = 0;
 
   // activate Timer1 overflow interrupt 
   TIMSK1 = 1 << TOIE1;
 
   // start serial port at 9600 bps:
   Serial.begin(9600);
 }
 
 void loop()
 {
   // if we get a valid byte, read analog ins:
   if (Serial.available() > 0) {
     // get incoming byte:
     inByte = Serial.read();
     Serial.print(inByte, BYTE);
     Serial.print("rn");
   }
 }

int inByte      = 0;    // incoming serial byte
int ppmPin      = 2;    // pin to make the waveform on
 
 
// to setup the device, we will initialize all the channels, and initialize the
// timer settings
void setup()
{
    // start serial port at 9600 bps, note that this also sets the Timer1
    // prescaler, so we need to ensure that we don't change it later; a test 
    // using a previous program showed that 9600 baud set the prescaler to 64
    // or the Timer1 control register B to 0x03.
    Serial.begin(9600);
 
    // we configure the signal pin as an input; not that the signal actually is
    // an input but we modify the signal by pulling it low when we need to
    pinMode(ppmPin, INPUT);
 
 
    // then we set the inital state of the pin to be low
    digitalWrite(ppmPin, LOW);
}
 
 
// the main routine monitors the serial port, and on receipt of a completed 
// packet will recalculate the compare points for the specified signal
void loop()
{
    // if there's a byte available on the serial port, then read it in
    if (Serial.available() > 0)
    {
        // get incoming byte
        inByte = Serial.read(); 
 
        switch(inByte)
        {
            case 'a':
                pinMode(ppmPin, OUTPUT);
                Serial.print("setting pin lown");
                break;
 
            case 'b':
                pinMode(ppmPin, INPUT);
                Serial.print("setting pin highn");
                break;
 
            default:
                break;
        }
    }
}

int inByte      = 0;    // incoming serial byte
int ppmPin      = 2;    // pin to make the waveform on
int chan[8];            // 8 channels encoded as 250 * (percent range)
 
int compA[9];           // 9 compare points for Timer1
int compB[9];           // 9 compare points for Timer2
int iCompA      = 0;    // compare point index for currently active
int iCompB      = 0;    // compare point index for currently active
 
 
// the 0xFF byte will serve as a packet delimeter, we don't want to read
// garbage from the serial so we'll start as soon as we get one of those but
// not before
int bDelimReceived  = 0;
 
// we don't want to write to any of the compare registers unless we have to 
// so we'll only do so at the end of a frame if that frame involved a change
// in the current signal
int bSignalChanged  = 0;
 
// index for which channel is next to read in
int iChan = 0;
 
 
// define the Timer1 compare match interrupt service routine for the rising 
// edge
ISR(TIMER1_COMPA_vect) 
{
    // to set the line high, we switch the pin mode to "INPUT"
    pinMode(ppmPin, INPUT);
 
 
    // if this is not the last rising edge
    if( iCompA < 8 )
    {
        // then we change the compare register to issue an interrupt at the next
        // rising edge, by incrementing the compare point counter
        iCompA++;
 
        // and then setting the compare register
        OCR1A = compA[iCompA];
    }
 
    // if this is the last rising edge then we need to set the compare
    // register to be at the time of the rising edge following the start 
    // frame
    else
    {
        // first, if the signal has changed since while writing the last frame
        // then we need to update the compare points
        if( bSignalChanged )
        {
            compA[0] = 3550;
            for(int i = 0; i < 8; i++)
                compA[0] -= chan[i];
 
            // the end of the first pulse is 75 ticks (300us) after that
            compB[0] = compA[0] + 75;
 
            // and then the rest of the compare points depend on the value of
            // each channel
            for(int i = 1; i < 9; i++ )
            {
                compA[i] = compB[i-1] + chan[i-1] + 175;
                compB[i] = compA[i] + 75;
            }
 
            bSignalChanged = 0;
        }
 
        // then we set the compare point to match the end of the start segment
        iCompA  = 0;
        OCR1A   = compA[0];
    }
 
}
 
// define the Timer1 compare match interrupt service routine for the falling 
// edge
ISR(TIMER1_COMPB_vect) 
{
    // to set the pin low we open the collector
    pinMode(ppmPin, OUTPUT);
 
 
    // if this is not the last falling edge
    if( iCompB < 8 )
    {
        // then we change the compare register to issue an interrupt at the next
        // rising edge, by incrementing the compare point counter
        iCompB++;
 
        // and then setting the compare register
        OCR1B = compB[iCompB];
    }
 
    // if this is the last falling edge
    else
    {
        // then we wrap around to the beginning
        iCompB=0;
 
        // and set the compare register
        OCR1B = compB[iCompB];
 
        // and we also need to reset the timer because this is the end of the 
        // frame
        TCNT1 = 0x00;
    }
 
}
 
 
 
 
 
 
// to setup the device, we will initialize all the channels, and initialize the
// timer settings
void setup()
{
    // initialize all eight channels to be at 125, or neutral
    for(int i=0; i < 8; i++)
        chan[i] = 125;
 
    // initialize the throttle to be "full left" which is actually "full stop"
    chan[2] = 0;
 
    // start serial port at 9600 bps, note that this also sets the Timer1
    // prescaler, so we need to ensure that we don't change it later; a test 
    // using a previous program showed that 9600 baud set the prescaler to 64
    // or the Timer1 control register B to 0x03.
    Serial.begin(9600);
 
    // set Timer1 to operate in "normal" Mode, and set the
    // prescaler to 64; the default mode is one of the PWM modes so we need to
    // set this
    TCCR1A = 0;
 
    // note: Timer0 and Timer1 share a prescaler, and Timer0 is used by the 
    // serial lines. Therefore, we cannot pick the value of the prescaler, 
    // rather it is determined by the baud rate we want. A simple program has 
    // shown that setting the baud rate to 9600 involves setting the prescaler 
    // to 64
 
    Serial.print("Timer Control Registers: n");
    Serial.print("   A: 0x");
    Serial.print(TCCR1A, HEX);
    Serial.print("n");
    Serial.print("   B: 0x");
    Serial.print(TCCR1B, HEX);
    Serial.print("n");
 
    // set the Timer1 output compare register A to 3550 ticks, which corresponds 
    // to 14,200us with the prescale set to 64; the math goes like this: 
    //    with the prescaler set to 64, the Timer1 period is 64/16e6 = 4us
    //    want an interrupt issued after 22.5ms - 8*700us - 9*300us = 14,200us
    //    means we want an interrupt issued after 14,200/4 = 3550 ticks
    compA[0] = 3550;
    OCR1A = compA[0];
 
    // set Timer1 output compare register B to something 300us/4us = 75 ticks 
    // after the first compare point for timer A
    compB[0] = compA[0] + 75;
    OCR1B = compB[0];
 
    // we can go ahead and initialize all the other compare points as well, we
    // know that all the channels are set to zero, but I'll do this the long 
    // way because it'll match code that we use elsewhere in this program
    for(int i=1; i < 9; i++)
    {
        compA[i] = compB[i-1] + chan[i-1] + 175;
        compB[i] = compA[i] + 75;
    }
 
    // activate Timer1 output compare interrupt with compare register A and
    // compare register B by setting the Output Compare Interrupt Enable bits
    TIMSK1 = 1 << OCIE1A | 1 << OCIE1B;
 
 
    // we configure the signal pin as an input; not that the signal actually is
    // an input but we modify the signal by an open collector so to make the
    // signal high we enable a 20K pull-up resistor, and to make the signal 
    // low we open the collector
    pinMode(ppmPin, INPUT);
 
 
    // then we set the inital state of the pin to be low
    digitalWrite(ppmPin, LOW);
}
 
 
 
// the main routine monitors the serial port, and on receipt of a completed 
// packet will recalculate the compare points for the specified signal
void loop()
{
    // if there's a byte available on the serial port, then read it in
    while (Serial.available() > 0)
    {
        // get incoming byte
        inByte = Serial.read(); 
 
        // if the byte is a packet delimiter, then start recording the new 
        // packet by resetting the channel indexer
        if( inByte == 0xFF )
        {
            bDelimReceived  = 1;
            iChan           = 0;
        }
 
        // otherwise, if we've recieved at least one packet delimiter and the
        // current channel index is valid, then record the chanel value; 
        else if(bDelimReceived && iChan < 8)
        {
            // we can save some processing time by only updating the stored 
            // values if the incoming command has changed, so we'll condition
            // the calculations on the fact that the byte is different than
            // what is already stored
            if(inByte != chan[iChan])
            {
                // the protocol is defined to send values between 0 and 250 
                // inclusive, for 250 distinct values; the timing increment is 
                // between 0 and 250 so we simply store the value
                chan[iChan] = inByte;
 
                // since the signal changed, we need to raise the flag
                bSignalChanged = true;
            }
 
            // then we increment the channel index so that we're ready for 
            // the next byte that's sent
            iChan++;
        }
    }
}

/**
 *  file       serialTest.cpp
 *  date:      Oct 27, 2009
 *  brief:
 *
 *  detail:
 *  This is a simple test program that demonstrates how to connect to and
 *  write commands to the arduino transmitter interface using windows.
 *
 *  the TxDuino is an interface into the futaba FP-TP-FM transmitter module,
 *  which accepts an RC PPM input. This signal contains a maximum of 8
 *  servo channels.
 */
 
#include <iostream>
#include <iomanip>
#include <cmath>
#include <windows.h>
 
#define PI 3.14159265
 
int main( int argc, char** argv )
{
    using std::cout;
    using std::endl;
    using std::sin;
    using std::setw;
 
    // check to ensure that the command line included a device to open
    if( argc < 2 )
    {
        cout << "Usage: serialTest.exe [Device Name]n"
                "   where [Device Name] is the name of the COM port file onn "
                "   windows (i.e. \\.\COM8), or the name of the serialn "
                "   device on *nix (i.e. /dev/tty8)n" << endl;
 
        return -1;
    }
 
    // grab a pointer to the device to open
    char*       strDevName = argv[1];
 
    // open the file using the windows API
    HANDLE      hComPort         =
    CreateFile( strDevName,
        GENERIC_READ | GENERIC_WRITE,       // access mode: read and write
        FILE_SHARE_READ|FILE_SHARE_WRITE,   // (sharing)
        NULL,                               // (security) 0: none
        OPEN_EXISTING,                      // (creation) i.e. don't make it
        0,                                  // (overlapped operation)
        NULL);                              // no template file
 
    // check to make sure the file open succeeded
    if( hComPort == INVALID_HANDLE_VALUE )
    {
        cout << "FATAL, Invalid device name: " << strDevName << "n" << endl;
        return -2;
    }
 
    // get the current settings on the com port
    DCB dcb;
    GetCommState( hComPort, &dcb );
 
    // change the settings, the TxDuino uses a BAUD rate of 9600
    dcb.fBinary     =   1;
    dcb.BaudRate    =   CBR_9600;
    dcb.Parity      =   NOPARITY;
    dcb.ByteSize    =   8;
    dcb.StopBits    =   ONESTOPBIT;
 
    // set the new settings for the port
    SetCommState( hComPort, &dcb );
 
    // allocate the data buffer for sending over serial
    unsigned char data[9];
 
    // set the last byte to be the stop byte
    data[8] = 0xFF;
 
    // send a sinusoidal input on all channels (except for channel 3, which is
    // usually the throttle) for 10 seconds
    for(int i=0; i < 1000; i++)
    {
        for(int j=0; j < 8; j++)
            data[j] = (unsigned char)(125.0 + 75.0 * sin( 2.0 * PI * i / 100.0 ));
 
        data[2] = 0;
        data[8] = 0xFF;
 
        for(int j=0; j < 8; j++)
            cout << setw(3) << (int)data[j] << " | ";
        cout << endl;
 
 
 
        DWORD bytesWritten;
 
        BOOL retVal =
        WriteFile(  hComPort,       // output handle
                    data,           // buffer of bytes to send
                    9,              // number of bytes to send from buffer
                    &bytesWritten,  // pointer to a word that recieves number of
                                    // bytes written
                    NULL);          // pointer to an OVERLAPPED struct
 
        Sleep(1);
    }
 
 
    // close the device
    CloseHandle( hComPort );
 
    return 0;
}