flightgear/src/Network/atc610x.cxx

// atc610x.cxx -- FGFS interface to ATC 610x hardware
//
// Written by Curtis Olson, started January 2002
//
// Copyright (C) 2002  Curtis L. Olson - curt@flightgear.org
//
// This program is free software; 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 2 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
// MERCHANTABILITY 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; if not, write to the Free Software
// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
//
// $Id$


#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#include <simgear/compiler.h>

#include <stdlib.h>		// atoi() atof() abs()
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>              //snprintf
#if defined( _MSC_VER ) || defined(__MINGW32__)
#  include <io.h>                 //lseek, read, write
#endif

#include STL_STRING

#include <plib/ul.h>

#include <simgear/debug/logstream.hxx>
#include <simgear/io/iochannel.hxx>
#include <simgear/math/sg_types.hxx>
#include <simgear/misc/props.hxx>
#include <simgear/misc/sg_path.hxx>

#include <Main/fg_props.hxx>
#include <Main/globals.hxx>

#include "atc610x.hxx"

SG_USING_STD(string);

// Lock the ATC 610 hardware
static int ATC610xLock( int fd ) {
    // rewind
    lseek( fd, 0, SEEK_SET );

    char tmp[2];
    int result = read( fd, tmp, 1 );
    if ( result != 1 ) {
	SG_LOG( SG_IO, SG_DEBUG, "Lock failed" );
    }

    return result;
}


// Write a radios command
static int ATC610xRelease( int fd ) {
    // rewind
    lseek( fd, 0, SEEK_SET );

    char tmp[2];
    tmp[0] = tmp[1] = 0;
    int result = write( fd, tmp, 1 );

    if ( result != 1 ) {
	SG_LOG( SG_IO, SG_DEBUG, "Release failed" );
    }

    return result;
}


// Read analog inputs
static void ATC610xReadAnalogInputs( int fd, unsigned char *analog_in_bytes ) {
    // rewind
    lseek( fd, 0, SEEK_SET );

    int result = read( fd, analog_in_bytes, ATC_ANAL_IN_BYTES );
    if ( result != ATC_ANAL_IN_BYTES ) {
	SG_LOG( SG_IO, SG_ALERT, "Read failed" );
	exit( -1 );
    }
}


// Write a radios command
static int ATC610xSetRadios( int fd,
			     unsigned char data[ATC_RADIO_DISPLAY_BYTES] )
{
    // rewind
    lseek( fd, 0, SEEK_SET );

    int result = write( fd, data, ATC_RADIO_DISPLAY_BYTES );

    if ( result != ATC_RADIO_DISPLAY_BYTES ) {
	SG_LOG( SG_IO, SG_DEBUG, "Write failed" );
    }

    return result;
}


// Read status of last radios written to
static void ATC610xReadRadios( int fd, unsigned char *switch_data ) {
    // rewind
    lseek( fd, 0, SEEK_SET );

    int result = read( fd, switch_data, ATC_RADIO_SWITCH_BYTES );
    if ( result != ATC_RADIO_SWITCH_BYTES ) {
	SG_LOG( SG_IO, SG_ALERT, "Read failed" );
	exit( -1 );
    }
}

// Write a stepper command
static int ATC610xSetStepper( int fd, unsigned char channel,
			      unsigned char value )
{
    // rewind
    lseek( fd, 0, SEEK_SET );

    // Write the value
    unsigned char buf[3];
    buf[0] = channel;
    buf[1] = value;
    buf[2] = 0;
    int result = write( fd, buf, 2 );
    if ( result != 2 ) {
	SG_LOG( SG_IO, SG_INFO, "Write failed" );
    }
    SG_LOG( SG_IO, SG_DEBUG,
	    "Sent cmd = " << (int)channel << " value = " << (int)value );
    return result;
}


// Read status of last stepper written to
static unsigned char ATC610xReadStepper( int fd ) {
    int result;

    // rewind
    lseek( fd, 0, SEEK_SET );

    // Write the value
    unsigned char buf[2];
    result = read( fd, buf, 1 );
    if ( result != 1 ) {
	SG_LOG( SG_IO, SG_ALERT, "Read failed" );
	exit( -1 );
    }
    SG_LOG( SG_IO, SG_DEBUG, "Read result = " << (int)buf[0] );

    return buf[0];
}


// Read switch inputs
static void ATC610xReadSwitches( int fd, unsigned char *switch_bytes ) {
    // rewind
    lseek( fd, 0, SEEK_SET );

    int result = read( fd, switch_bytes, ATC_SWITCH_BYTES );
    if ( result != ATC_SWITCH_BYTES ) {
	SG_LOG( SG_IO, SG_ALERT, "Read failed" );
	exit( -1 );
    }
}


// Turn a lamp on or off
void ATC610xSetLamp( int fd, int channel, bool value ) {
    // lamp channels 0-63 are written to LampPort0, channels 64-127
    // are written to LampPort1

    // bits 0-6 are the lamp address
    // bit 7 is the value (on/off)

    int result;

    // Write the value
    unsigned char buf[3];
    buf[0] = channel;
    buf[1] = value;
    buf[2] = 0;
    result = write( fd, buf, 2 );
    if ( result != 2 ) {
        SG_LOG( SG_IO, SG_ALERT,  "Write failed" );
        exit( -1 );
    }
}


void FGATC610x::init_config() {
#if defined( unix ) || defined( __CYGWIN__ )
    // Next check home directory for .fgfsrc.hostname file
    char *envp = ::getenv( "HOME" );
    if ( envp != NULL ) {
        SGPath atc610x_config( envp );
        atc610x_config.append( ".fgfs-atc610x.xml" );
        readProperties( atc610x_config.str(), globals->get_props() );
    }
#endif
}


// Open and initialize ATC 610x hardware
bool FGATC610x::open() {
    if ( is_enabled() ) {
	SG_LOG( SG_IO, SG_ALERT, "This shouldn't happen, but the channel " 
		<< "is already in use, ignoring" );
	return false;
    }

    // This loads the config parameters generated by "simcal"
    init_config();

    SG_LOG( SG_IO, SG_ALERT,
	    "Initializing ATC 610x hardware, please wait ..." );

    set_hz( 30 );		// default to processing requests @ 30Hz
    set_enabled( true );

    board = 0;			// 610x uses a single board number = 0

    snprintf( lock_file, 256, "/proc/atc610x/board%d/lock", board );
    snprintf( analog_in_file, 256, "/proc/atc610x/board%d/analog_in", board );
    snprintf( lamps_file, 256, "/proc/atc610x/board%d/lamps", board );
    snprintf( radios_file, 256, "/proc/atc610x/board%d/radios", board );
    snprintf( stepper_file, 256, "/proc/atc610x/board%d/steppers", board );
    snprintf( switches_file, 256, "/proc/atc610x/board%d/switches", board );

    /////////////////////////////////////////////////////////////////////
    // Open the /proc files
    /////////////////////////////////////////////////////////////////////

    lock_fd = ::open( lock_file, O_RDWR );
    if ( lock_fd == -1 ) {
	SG_LOG( SG_IO, SG_ALERT, "errno = " << errno );
	char msg[256];
	snprintf( msg, 256, "Error opening %s", lock_file );
	perror( msg );
	exit( -1 );
    }

    analog_in_fd = ::open( analog_in_file, O_RDONLY );
    if ( analog_in_fd == -1 ) {
	SG_LOG( SG_IO, SG_ALERT, "errno = " << errno );
	char msg[256];
	snprintf( msg, 256, "Error opening %s", analog_in_file );
	perror( msg );
	exit( -1 );
    }

    lamps_fd = ::open( lamps_file, O_WRONLY );
    if ( lamps_fd == -1 ) {
	SG_LOG( SG_IO, SG_ALERT, "errno = " << errno );
	char msg[256];
	snprintf( msg, 256, "Error opening %s", lamps_file );
	perror( msg );
	exit( -1 );
    }

    radios_fd = ::open( radios_file, O_RDWR );
    if ( radios_fd == -1 ) {
	SG_LOG( SG_IO, SG_ALERT, "errno = " << errno );
	char msg[256];
	snprintf( msg, 256, "Error opening %s", radios_file );
	perror( msg );
	exit( -1 );
    }

    stepper_fd = ::open( stepper_file, O_RDWR );
    if ( stepper_fd == -1 ) {
	SG_LOG( SG_IO, SG_ALERT, "errno = " << errno );
	char msg[256];
	snprintf( msg, 256, "Error opening %s", stepper_file );
	perror( msg );
	exit( -1 );
    }

    switches_fd = ::open( switches_file, O_RDONLY );
    if ( switches_fd == -1 ) {
	SG_LOG( SG_IO, SG_ALERT, "errno = " << errno );
	char msg[256];
	snprintf( msg, 256, "Error opening %s", switches_file );
	perror( msg );
	exit( -1 );
    }

    /////////////////////////////////////////////////////////////////////
    // Home the compass stepper motor
    /////////////////////////////////////////////////////////////////////

    SG_LOG( SG_IO, SG_ALERT,
	    "  - Homing the compass stepper motor" );

    // Lock the hardware, keep trying until we succeed
    while ( ATC610xLock( lock_fd ) <= 0 );

    // Send the stepper home command
    ATC610xSetStepper( stepper_fd, ATC_COMPASS_CH, ATC_STEPPER_HOME );

    // Release the hardware
    ATC610xRelease( lock_fd );

    SG_LOG( SG_IO, SG_ALERT,
	    "  - Waiting for compass to come home." );

    bool home = false;
    int timeout = 900;          // about 30 seconds
    while ( ! home && timeout > 0 ) {
        if ( timeout % 150 == 0 ) {
            SG_LOG( SG_IO, SG_INFO, "waiting for compass = " << timeout );
        } else {
            SG_LOG( SG_IO, SG_DEBUG, "Checking if compass home ..." );
        }

	while ( ATC610xLock( lock_fd ) <= 0 );

	unsigned char result = ATC610xReadStepper( stepper_fd );
	if ( result == 0 ) {
	    home = true;
	}

	ATC610xRelease( lock_fd );

#if defined( _MSC_VER )
	ulMilliSecondSleep(33);
#elif defined (WIN32) && !defined(__CYGWIN__)
        Sleep (33);
#else
	usleep(33);
#endif

        --timeout;
    }

    compass_position = 0.0;

    /////////////////////////////////////////////////////////////////////
    // Blank the radio display
    /////////////////////////////////////////////////////////////////////

    SG_LOG( SG_IO, SG_ALERT,
	    "  - Clearing the radios displays." );

    // Prepair the data
    unsigned char value = 0xff;
    for ( int channel = 0; channel < ATC_RADIO_DISPLAY_BYTES; ++channel ) {
	radio_display_data[channel] = value;
    }

    // Lock the hardware, keep trying until we succeed
    while ( ATC610xLock( lock_fd ) <= 0 );

    // Set radio display
    ATC610xSetRadios( radios_fd, radio_display_data );

    ATC610xRelease( lock_fd );

    /////////////////////////////////////////////////////////////////////
    // Blank the lamps
    /////////////////////////////////////////////////////////////////////

    for ( int i = 0; i < 128; ++i ) {
        ATC610xSetLamp( lamps_fd, i, false );
    }

    /////////////////////////////////////////////////////////////////////
    // Finished initing hardware
    /////////////////////////////////////////////////////////////////////

    SG_LOG( SG_IO, SG_ALERT,
	    "Done initializing ATC 610x hardware." );

    /////////////////////////////////////////////////////////////////////
    // Connect up to property values
    /////////////////////////////////////////////////////////////////////

    mag_compass = fgGetNode( "/steam/mag-compass-deg", true );

    dme_min = fgGetNode( "/radios/dme/ete-min", true );
    dme_kt = fgGetNode( "/radios/dme/speed-kt", true );
    dme_nm = fgGetNode( "/radios/dme/distance-nm", true );

    navcom1_power = fgGetNode( "/radios/comm[0]/inputs/power-btn", true );
    navcom2_power = fgGetNode( "/radios/comm[1]/inputs/power-btn", true );

    com1_freq = fgGetNode( "/radios/comm[0]/frequencies/selected-mhz", true );
    com1_stby_freq
	= fgGetNode( "/radios/comm[0]/frequencies/standby-mhz", true );

    com2_freq = fgGetNode( "/radios/comm[1]/frequencies/selected-mhz", true );
    com2_stby_freq
	= fgGetNode( "/radios/comm[1]/frequencies/standby-mhz", true );

    nav1_freq = fgGetNode( "/radios/nav[0]/frequencies/selected-mhz", true );
    nav1_stby_freq
	= fgGetNode( "/radios/nav[0]/frequencies/standby-mhz", true );

    nav2_freq = fgGetNode( "/radios/nav[1]/frequencies/selected-mhz", true );
    nav2_stby_freq
	= fgGetNode( "/radios/nav[1]/frequencies/standby-mhz", true );

    adf_power = fgGetNode( "/radios/kr-87/inputs/power-btn", true );
    adf_vol = fgGetNode( "/radios/kr-87/inputs/volume", true );
    adf_adf_btn = fgGetNode( "/radios/kr-87/inputs/adf-btn", true );
    adf_bfo_btn = fgGetNode( "/radios/kr-87/inputs/bfo-btn", true );
    adf_freq = fgGetNode( "/radios/kr-87/outputs/selected-khz", true );
    adf_stby_freq = fgGetNode( "/radios/kr-87/outputs/standby-khz", true );
    adf_stby_mode = fgGetNode( "/radios/kr-87/modes/stby", true );
    adf_timer_mode = fgGetNode( "/radios/kr-87/modes/timer", true );
    adf_count_mode = fgGetNode( "/radios/kr-87/modes/count", true );
    adf_flight_timer = fgGetNode( "/radios/kr-87/outputs/flight-timer", true );
    adf_elapsed_timer = fgGetNode( "/radios/kr-87/outputs/elapsed-timer",
                                   true );
    adf_ant_ann = fgGetNode( "/radios/kr-87/annunciators/ant", true );
    adf_adf_ann = fgGetNode( "/radios/kr-87/annunciators/adf", true );
    adf_bfo_ann = fgGetNode( "/radios/kr-87/annunciators/bfo", true );
    adf_frq_ann = fgGetNode( "/radios/kr-87/annunciators/frq", true );
    adf_flt_ann = fgGetNode( "/radios/kr-87/annunciators/flt", true );
    adf_et_ann = fgGetNode( "/radios/kr-87/annunciators/et", true );

    inner = fgGetNode( "/radios/marker-beacon/inner", true );
    middle = fgGetNode( "/radios/marker-beacon/middle", true );
    outer = fgGetNode( "/radios/marker-beacon/outer", true );

    xpdr_ident_btn = fgGetNode( "/radios/kt-70/inputs/ident-btn", true );
    xpdr_digit1 = fgGetNode( "/radios/kt-70/inputs/digit1", true );
    xpdr_digit2 = fgGetNode( "/radios/kt-70/inputs/digit2", true );
    xpdr_digit3 = fgGetNode( "/radios/kt-70/inputs/digit3", true );
    xpdr_digit4 = fgGetNode( "/radios/kt-70/inputs/digit4", true );
    xpdr_func_knob = fgGetNode( "/radios/kt-70/inputs/func-knob", true );
    xpdr_id_code = fgGetNode( "/radios/kt-70/outputs/id-code", true );
    xpdr_flight_level = fgGetNode( "/radios/kt-70/outputs/flight-level", true );
    xpdr_fl_ann = fgGetNode( "/radios/kt-70/annunciators/fl", true );
    xpdr_alt_ann = fgGetNode( "/radios/kt-70/annunciators/alt", true );
    xpdr_gnd_ann = fgGetNode( "/radios/kt-70/annunciators/gnd", true );
    xpdr_on_ann = fgGetNode( "/radios/kt-70/annunciators/on", true );
    xpdr_sby_ann = fgGetNode( "/radios/kt-70/annunciators/sby", true );
    xpdr_reply_ann = fgGetNode( "/radios/kt-70/annunciators/reply", true );

    elevator_center = fgGetNode( "/input/atc610x/elevator/center", 0 );
    elevator_min = fgGetNode( "/input/atc610x/elevator/min", 0 );
    elevator_max = fgGetNode( "/input/atc610x/elevator/max", 0 );

    ailerons_center = fgGetNode( "/input/atc610x/ailerons/center", 0 );
    ailerons_min = fgGetNode( "/input/atc610x/ailerons/min", 0 );
    ailerons_max = fgGetNode( "/input/atc610x/ailerons/max", 0 );

    rudder_center = fgGetNode( "/input/atc610x/rudder/center", 0 );
    rudder_min = fgGetNode( "/input/atc610x/rudder/min", 0 );
    rudder_max = fgGetNode( "/input/atc610x/rudder/max", 0 );

    throttle_min = fgGetNode( "/input/atc610x/throttle/min", 0 );
    throttle_max = fgGetNode( "/input/atc610x/throttle/max", 0 );

    mixture_min = fgGetNode( "/input/atc610x/mixture/min", 0 );
    mixture_max = fgGetNode( "/input/atc610x/mixture/max", 0 );

    trim_center = fgGetNode( "/input/atc610x/trim/center", 0 );
    trim_min = fgGetNode( "/input/atc610x/trim/min", 0 );
    trim_max = fgGetNode( "/input/atc610x/trim/max", 0 );

    nav1vol_min = fgGetNode( "/input/atc610x/nav1vol/min", 0 );
    nav1vol_max = fgGetNode( "/input/atc610x/nav1vol/max", 0 );

    nav2vol_min = fgGetNode( "/input/atc610x/nav2vol/min", 0 );
    nav2vol_max = fgGetNode( "/input/atc610x/nav2vol/max", 0 );

    return true;
}


/////////////////////////////////////////////////////////////////////
// Read analog inputs
/////////////////////////////////////////////////////////////////////

#define ATC_AILERON_CENTER 535
#define ATC_ELEVATOR_TRIM_CENTER 512
#define ATC_ELEVATOR_CENTER 543
#define ATC_RUDDER_CENTER 519

// scale a number between min and max (with center defined) to a scale
// from -1.0 to 1.0
static double scale( int center, int min, int max, int value ) {
    // cout << center << " " << min << " " << max << " " << value << " ";
    double result;
    double range;

    if ( value <= center ) {
        range = center - min;
        result = (value - center) / range;
    } else {
        range = max - center;
        result = (value - center) / range;            
    }

    if ( result < -1.0 ) result = -1.0;
    if ( result > 1.0 ) result = 1.0;

    // cout << result << endl;

    return result;
}


// scale a number between min and max to a scale from 0.0 to 1.0
static double scale( int min, int max, int value ) {
    // cout << center << " " << min << " " << max << " " << value << " ";
    double result;
    double range;

    range = max - min;
    result = (value - min) / range;

    if ( result < 0.0 ) result = 0.0;
    if ( result > 1.0 ) result = 1.0;

    // cout << result << endl;

    return result;
}


bool FGATC610x::do_analog_in() {
    // Read raw data in byte form
    ATC610xReadAnalogInputs( analog_in_fd, analog_in_bytes );

    // Convert to integer values
    for ( int channel = 0; channel < ATC_ANAL_IN_VALUES; ++channel ) {
	unsigned char hi = analog_in_bytes[2 * channel] & 0x03;
	unsigned char lo = analog_in_bytes[2 * channel + 1];
	analog_in_data[channel] = hi * 256 + lo;

	// printf("%02x %02x ", hi, lo );
	// printf("%04d ", value );
    }

    float tmp, tmp1, tmp2;

    // aileron
    tmp = scale( ailerons_center->getIntValue(), ailerons_min->getIntValue(),
                 ailerons_max->getIntValue(), analog_in_data[0] );
    fgSetFloat( "/controls/aileron", tmp );
    // cout << "aileron = " << analog_in_data[0] << " = " << tmp;

    // elevator
    tmp = -scale( elevator_center->getIntValue(), elevator_min->getIntValue(),
                  elevator_max->getIntValue(), analog_in_data[5] );
    fgSetFloat( "/controls/elevator", tmp );
    // cout << "trim = " << analog_in_data[4] << " = " << tmp;

    // elevator trim
    tmp = scale( trim_center->getIntValue(), trim_min->getIntValue(),
                 trim_max->getIntValue(), analog_in_data[4] );
    fgSetFloat( "/controls/elevator-trim", tmp );
    // cout << " elev = " << analog_in_data[5] << " = " << tmp << endl;

    // mixture
    tmp = scale( mixture_min->getIntValue(), mixture_max->getIntValue(),
                 analog_in_data[7] );
    fgSetFloat( "/controls/mixture[0]", tmp );
    fgSetFloat( "/controls/mixture[1]", tmp );

    // throttle
    tmp = scale( mixture_min->getIntValue(), mixture_max->getIntValue(),
                 analog_in_data[8] );
    fgSetFloat( "/controls/throttle[0]", tmp );
    fgSetFloat( "/controls/throttle[1]", tmp );

#if 0
    // rudder
    tmp = scale( rudder_center->getIntValue(), rudder_min->getIntValue(),
                 rudder_max->getIntValue(), analog_in_data[10] );
    fgSetFloat( "/controls/rudder", tmp );
#endif

    // nav1 volume
    tmp = (float)analog_in_data[25] / 1024.0f;
    fgSetFloat( "/radios/nav[0]/volume", tmp );

    // nav2 volume
    tmp = (float)analog_in_data[24] / 1024.0f;
    fgSetFloat( "/radios/nav[1]/volume", tmp );

    // adf volume
    tmp = (float)analog_in_data[26] / 1024.0f;
    fgSetFloat( "/radios/kr-87/inputs/volume", tmp );

    // nav2 obs tuner
    tmp = (float)analog_in_data[29] * 360.0f / 1024.0f;
    fgSetFloat( "/radios/nav[1]/radials/selected-deg", tmp );

    // nav1 obs tuner
    tmp1 = (float)analog_in_data[30] * 360.0f / 1024.0f;
    tmp2 = (float)analog_in_data[31] * 360.0f / 1024.0f;
    fgSetFloat( "/radios/nav[0]/radials/selected-deg", tmp1 );

    return true;
}


/////////////////////////////////////////////////////////////////////
// Write the lights
/////////////////////////////////////////////////////////////////////

bool FGATC610x::do_lights() {

    // Marker beacons
    ATC610xSetLamp( lamps_fd, 4, inner->getBoolValue() );
    ATC610xSetLamp( lamps_fd, 5, middle->getBoolValue() );
    ATC610xSetLamp( lamps_fd, 3, outer->getBoolValue() );

    // ADF annunciators
    ATC610xSetLamp( lamps_fd, 11, adf_ant_ann->getBoolValue() ); // ANT
    ATC610xSetLamp( lamps_fd, 12, adf_adf_ann->getBoolValue() ); // ADF
    ATC610xSetLamp( lamps_fd, 13, adf_bfo_ann->getBoolValue() ); // BFO
    ATC610xSetLamp( lamps_fd, 14, adf_frq_ann->getBoolValue() ); // FRQ
    ATC610xSetLamp( lamps_fd, 15, adf_flt_ann->getBoolValue() ); // FLT
    ATC610xSetLamp( lamps_fd, 16, adf_et_ann->getBoolValue() ); // ET

    // Transponder annunciators
    ATC610xSetLamp( lamps_fd, 17, xpdr_fl_ann->getBoolValue() ); // FL
    ATC610xSetLamp( lamps_fd, 18, xpdr_alt_ann->getBoolValue() ); // ALT
    ATC610xSetLamp( lamps_fd, 19, xpdr_gnd_ann->getBoolValue() ); // GND
    ATC610xSetLamp( lamps_fd, 20, xpdr_on_ann->getBoolValue() ); // ON
    ATC610xSetLamp( lamps_fd, 21, xpdr_sby_ann->getBoolValue() ); // SBY
    ATC610xSetLamp( lamps_fd, 22, xpdr_reply_ann->getBoolValue() ); // R

    return true;
}


/////////////////////////////////////////////////////////////////////
// Read radio switches 
/////////////////////////////////////////////////////////////////////

bool FGATC610x::do_radio_switches() {
    double freq, coarse_freq, fine_freq, value;
    int diff;

    ATC610xReadRadios( radios_fd, radio_switch_data );

    // DME Switch
    dme_switch = (radio_switch_data[7] >> 4) & 0x03;
    if ( dme_switch == 0 ) {
	// off
	fgSetInt( "/radios/dme/switch-position", 0 );
    } else if ( dme_switch == 2 ) {
	// nav1
	fgSetInt( "/radios/dme/switch-position", 1 );
    } else if ( dme_switch == 1 ) {
	// nav2
	fgSetInt( "/radios/dme/switch-position", 3 );
    }

    // NavCom1 Power
    fgSetBool( "/radios/comm[0]/inputs/power-btn",
               radio_switch_data[7] & 0x01 );

    if ( navcom1_power->getBoolValue() ) {
        // Com1 Swap
        int com1_swap = !((radio_switch_data[7] >> 1) & 0x01);
        static int last_com1_swap;
        if ( com1_swap && (last_com1_swap != com1_swap) ) {
            float tmp = com1_freq->getFloatValue();
            fgSetFloat( "/radios/comm[0]/frequencies/selected-mhz",
                        com1_stby_freq->getFloatValue() );
            fgSetFloat( "/radios/comm[0]/frequencies/standby-mhz", tmp );
        }
        last_com1_swap = com1_swap;
    }

    // NavCom2 Power
    fgSetBool( "/radios/comm[1]/inputs/power-btn",
               radio_switch_data[15] & 0x01 );

    if ( navcom2_power->getBoolValue() ) {
        // Com2 Swap
        int com2_swap = !((radio_switch_data[15] >> 1) & 0x01);
        static int last_com2_swap;
        if ( com2_swap && (last_com2_swap != com2_swap) ) {
            float tmp = com2_freq->getFloatValue();
            fgSetFloat( "/radios/comm[1]/frequencies/selected-mhz",
                        com2_stby_freq->getFloatValue() );
            fgSetFloat( "/radios/comm[1]/frequencies/standby-mhz", tmp );
        }
        last_com2_swap = com2_swap;
    }

    if ( navcom1_power->getBoolValue() ) {
        // Nav1 Swap
        int nav1_swap = radio_switch_data[11] & 0x01;
        static int last_nav1_swap;
        if ( nav1_swap && (last_nav1_swap != nav1_swap) ) {
            float tmp = nav1_freq->getFloatValue();
            fgSetFloat( "/radios/nav[0]/frequencies/selected-mhz",
                        nav1_stby_freq->getFloatValue() );
            fgSetFloat( "/radios/nav[0]/frequencies/standby-mhz", tmp );
        }
        last_nav1_swap = nav1_swap;
    }

    if ( navcom2_power->getBoolValue() ) {
        // Nav2 Swap
        int nav2_swap = !(radio_switch_data[19] & 0x01);
        static int last_nav2_swap;
        if ( nav2_swap && (last_nav2_swap != nav2_swap) ) {
            float tmp = nav2_freq->getFloatValue();
            fgSetFloat( "/radios/nav[1]/frequencies/selected-mhz",
                        nav2_stby_freq->getFloatValue() );
            fgSetFloat( "/radios/nav[1]/frequencies/standby-mhz", tmp );
        }
        last_nav2_swap = nav2_swap;
    }

    if ( navcom1_power->getBoolValue() ) {
        // Com1 Tuner
        int com1_tuner_fine = ((radio_switch_data[5] >> 4) & 0x0f) - 1;
        int com1_tuner_coarse = (radio_switch_data[5] & 0x0f) - 1;
        static int last_com1_tuner_fine = com1_tuner_fine;
        static int last_com1_tuner_coarse = com1_tuner_coarse;

        freq = com1_stby_freq->getFloatValue();
        coarse_freq = (int)freq;
        fine_freq = (int)((freq - coarse_freq) * 40 + 0.5);

        if ( com1_tuner_fine != last_com1_tuner_fine ) {
            diff = com1_tuner_fine - last_com1_tuner_fine;
            if ( abs(diff) > 4 ) {
                // roll over
                if ( com1_tuner_fine < last_com1_tuner_fine ) {
                    // going up
                    diff = 12 - last_com1_tuner_fine + com1_tuner_fine;
                } else {
                    // going down
                    diff = com1_tuner_fine - 12 - last_com1_tuner_fine;
                }
            }
            fine_freq += diff;
        }
        while ( fine_freq >= 40.0 ) { fine_freq -= 40.0; }
        while ( fine_freq < 0.0 )  { fine_freq += 40.0; }

        if ( com1_tuner_coarse != last_com1_tuner_coarse ) {
            diff = com1_tuner_coarse - last_com1_tuner_coarse;
            if ( abs(diff) > 4 ) {
                // roll over
                if ( com1_tuner_coarse < last_com1_tuner_coarse ) {
                    // going up
                    diff = 12 - last_com1_tuner_coarse + com1_tuner_coarse;
                } else {
                    // going down
                    diff = com1_tuner_coarse - 12 - last_com1_tuner_coarse;
                }
            }
            coarse_freq += diff;
        }
        if ( coarse_freq < 118.0 ) { coarse_freq += 19.0; }
        if ( coarse_freq > 136.0 ) { coarse_freq -= 19.0; }

        last_com1_tuner_fine = com1_tuner_fine;
        last_com1_tuner_coarse = com1_tuner_coarse;

        fgSetFloat( "/radios/comm[0]/frequencies/standby-mhz", 
                    coarse_freq + fine_freq / 40.0 );
    }

    if ( navcom2_power->getBoolValue() ) {
        // Com2 Tuner
        int com2_tuner_fine = ((radio_switch_data[13] >> 4) & 0x0f) - 1;
        int com2_tuner_coarse = (radio_switch_data[13] & 0x0f) - 1;
        static int last_com2_tuner_fine = com2_tuner_fine;
        static int last_com2_tuner_coarse = com2_tuner_coarse;

        freq = com2_stby_freq->getFloatValue();
        coarse_freq = (int)freq;
        fine_freq = (int)((freq - coarse_freq) * 40 + 0.5);

        if ( com2_tuner_fine != last_com2_tuner_fine ) {
            diff = com2_tuner_fine - last_com2_tuner_fine;
            if ( abs(diff) > 4 ) {
                // roll over
                if ( com2_tuner_fine < last_com2_tuner_fine ) {
                    // going up
                    diff = 12 - last_com2_tuner_fine + com2_tuner_fine;
                } else {
                    // going down
                    diff = com2_tuner_fine - 12 - last_com2_tuner_fine;
                }
            }
            fine_freq += diff;
        }
        while ( fine_freq >= 40.0 ) { fine_freq -= 40.0; }
        while ( fine_freq < 0.0 )  { fine_freq += 40.0; }

        if ( com2_tuner_coarse != last_com2_tuner_coarse ) {
            diff = com2_tuner_coarse - last_com2_tuner_coarse;
            if ( abs(diff) > 4 ) {
                // roll over
                if ( com2_tuner_coarse < last_com2_tuner_coarse ) {
                    // going up
                    diff = 12 - last_com2_tuner_coarse + com2_tuner_coarse;
                } else {
                    // going down
                    diff = com2_tuner_coarse - 12 - last_com2_tuner_coarse;
                }
            }
            coarse_freq += diff;
        }
        if ( coarse_freq < 118.0 ) { coarse_freq += 19.0; }
        if ( coarse_freq > 136.0 ) { coarse_freq -= 19.0; }

        last_com2_tuner_fine = com2_tuner_fine;
        last_com2_tuner_coarse = com2_tuner_coarse;

        fgSetFloat( "/radios/comm[1]/frequencies/standby-mhz",
                    coarse_freq + fine_freq / 40.0 );
    }

    if ( navcom1_power->getBoolValue() ) {
        // Nav1 Tuner
        int nav1_tuner_fine = ((radio_switch_data[9] >> 4) & 0x0f) - 1;
        int nav1_tuner_coarse = (radio_switch_data[9] & 0x0f) - 1;
        static int last_nav1_tuner_fine = nav1_tuner_fine;
        static int last_nav1_tuner_coarse = nav1_tuner_coarse;

        freq = nav1_stby_freq->getFloatValue();
        coarse_freq = (int)freq;
        fine_freq = (int)((freq - coarse_freq) * 20 + 0.5);

        if ( nav1_tuner_fine != last_nav1_tuner_fine ) {
            diff = nav1_tuner_fine - last_nav1_tuner_fine;
            if ( abs(diff) > 4 ) {
                // roll over
                if ( nav1_tuner_fine < last_nav1_tuner_fine ) {
                    // going up
                    diff = 12 - last_nav1_tuner_fine + nav1_tuner_fine;
                } else {
                    // going down
                    diff = nav1_tuner_fine - 12 - last_nav1_tuner_fine;
                }
            }
            fine_freq += diff;
        }
        while ( fine_freq >= 20.0 ) { fine_freq -= 20.0; }
        while ( fine_freq < 0.0 )  { fine_freq += 20.0; }

        if ( nav1_tuner_coarse != last_nav1_tuner_coarse ) {
            diff = nav1_tuner_coarse - last_nav1_tuner_coarse;
            if ( abs(diff) > 4 ) {
                // roll over
                if ( nav1_tuner_coarse < last_nav1_tuner_coarse ) {
                    // going up
                    diff = 12 - last_nav1_tuner_coarse + nav1_tuner_coarse;
                } else {
                    // going down
                    diff = nav1_tuner_coarse - 12 - last_nav1_tuner_coarse;
                }
            }
            coarse_freq += diff;
        }
        if ( coarse_freq < 108.0 ) { coarse_freq += 10.0; }
        if ( coarse_freq > 117.0 ) { coarse_freq -= 10.0; }

        last_nav1_tuner_fine = nav1_tuner_fine;
        last_nav1_tuner_coarse = nav1_tuner_coarse;

        fgSetFloat( "/radios/nav[0]/frequencies/standby-mhz",
                    coarse_freq + fine_freq / 20.0 );
    }

    if ( navcom2_power->getBoolValue() ) {
        // Nav2 Tuner
        int nav2_tuner_fine = ((radio_switch_data[17] >> 4) & 0x0f) - 1;
        int nav2_tuner_coarse = (radio_switch_data[17] & 0x0f) - 1;
        static int last_nav2_tuner_fine = nav2_tuner_fine;
        static int last_nav2_tuner_coarse = nav2_tuner_coarse;

        freq = nav2_stby_freq->getFloatValue();
        coarse_freq = (int)freq;
        fine_freq = (int)((freq - coarse_freq) * 20 + 0.5);

        if ( nav2_tuner_fine != last_nav2_tuner_fine ) {
            diff = nav2_tuner_fine - last_nav2_tuner_fine;
            if ( abs(diff) > 4 ) {
                // roll over
                if ( nav2_tuner_fine < last_nav2_tuner_fine ) {
                    // going up
                    diff = 12 - last_nav2_tuner_fine + nav2_tuner_fine;
                } else {
                    // going down
                    diff = nav2_tuner_fine - 12 - last_nav2_tuner_fine;
                }
            }
            fine_freq += diff;
        }
        while ( fine_freq >= 20.0 ) { fine_freq -= 20.0; }
        while ( fine_freq < 0.0 )  { fine_freq += 20.0; }

        if ( nav2_tuner_coarse != last_nav2_tuner_coarse ) {
            diff = nav2_tuner_coarse - last_nav2_tuner_coarse;
            if ( abs(diff) > 4 ) {
                // roll over
                if ( nav2_tuner_coarse < last_nav2_tuner_coarse ) {
                    // going up
                    diff = 12 - last_nav2_tuner_coarse + nav2_tuner_coarse;
                } else {
                    // going down
                    diff = nav2_tuner_coarse - 12 - last_nav2_tuner_coarse;
                }
            }
            coarse_freq += diff;
        }
        if ( coarse_freq < 108.0 ) { coarse_freq += 10.0; }
        if ( coarse_freq > 117.0 ) { coarse_freq -= 10.0; }

        last_nav2_tuner_fine = nav2_tuner_fine;
        last_nav2_tuner_coarse = nav2_tuner_coarse;

        fgSetFloat( "/radios/nav[1]/frequencies/standby-mhz", 
                    coarse_freq + fine_freq / 20.0);
    }

    if ( adf_power->getBoolValue() ) {
        // ADF Tuner
        int adf_tuner_fine = ((radio_switch_data[21] >> 4) & 0x0f) - 1;
        int adf_tuner_coarse = (radio_switch_data[21] & 0x0f) - 1;
        static int last_adf_tuner_fine = adf_tuner_fine;
        static int last_adf_tuner_coarse = adf_tuner_coarse;

        // cout << "adf_stby_mode = " << adf_stby_mode->getIntValue() << endl;
        if ( adf_count_mode->getIntValue() == 2 ) {
            // tune count down timer
            value = adf_elapsed_timer->getDoubleValue();
        } else {
            // tune frequency
            if ( adf_stby_mode->getIntValue() == 1 ) {
                value = adf_freq->getFloatValue();
            } else {
                value = adf_stby_freq->getFloatValue();
            }
        }

        if ( adf_tuner_fine != last_adf_tuner_fine ) {
            diff = adf_tuner_fine - last_adf_tuner_fine;
            if ( abs(diff) > 4 ) {
                // roll over
                if ( adf_tuner_fine < last_adf_tuner_fine ) {
                    // going up
                    diff = 12 - last_adf_tuner_fine + adf_tuner_fine;
                } else {
                    // going down
                    diff = adf_tuner_fine - 12 - last_adf_tuner_fine;
                }
            }
            value += diff;
        }

        if ( adf_tuner_coarse != last_adf_tuner_coarse ) {
            diff = adf_tuner_coarse - last_adf_tuner_coarse;
            if ( abs(diff) > 4 ) {
                // roll over
                if ( adf_tuner_coarse < last_adf_tuner_coarse ) {
                    // going up
                    diff = 12 - last_adf_tuner_coarse + adf_tuner_coarse;
                } else {
                    // going down
                    diff = adf_tuner_coarse - 12 - last_adf_tuner_coarse;
                }
            }
            if ( adf_count_mode->getIntValue() == 2 ) {
                value += 60 * diff;
            } else {
                value += 25 * diff;
            }
        }
        if ( adf_count_mode->getIntValue() == 2 ) {
            if ( value < 0 ) { value += 3600; }
            if ( value > 3599 ) { value -= 3600; }
        } else {
            if ( value < 200 ) { value += 1600; }
            if ( value > 1799 ) { value -= 1600; }
        }
 
        last_adf_tuner_fine = adf_tuner_fine;
        last_adf_tuner_coarse = adf_tuner_coarse;

        if ( adf_count_mode->getIntValue() == 2 ) {
            fgSetFloat( "/radios/kr-87/outputs/elapsed-timer", value );
        } else {
            if ( adf_stby_mode->getIntValue() == 1 ) {
                fgSetFloat( "/radios/kr-87/outputs/selected-khz", value );
            } else {
                fgSetFloat( "/radios/kr-87/outputs/standby-khz", value );
            }
        }
    }

    // ADF buttons 
    fgSetInt( "/radios/kr-87/inputs/adf-btn",
              !(radio_switch_data[23] & 0x01) );
    fgSetInt( "/radios/kr-87/inputs/bfo-btn",
              !(radio_switch_data[23] >> 1 & 0x01) );
    fgSetInt( "/radios/kr-87/inputs/frq-btn",
              (radio_switch_data[23] >> 2 & 0x01) );
    fgSetInt( "/radios/kr-87/inputs/flt-et-btn",
                  !(radio_switch_data[23] >> 3 & 0x01) );
    fgSetInt( "/radios/kr-87/inputs/set-rst-btn",
              !(radio_switch_data[23] >> 4 & 0x01) );
    fgSetInt( "/radios/kr-87/inputs/power-btn",
              radio_switch_data[23] >> 5 & 0x01 );
    /* cout << "adf = " << !(radio_switch_data[23] & 0x01)
         << " bfo = " << !(radio_switch_data[23] >> 1 & 0x01)
         << " stby = " << !(radio_switch_data[23] >> 2 & 0x01)
         << " timer = " << !(radio_switch_data[23] >> 3 & 0x01)
         << " set/rst = " << !(radio_switch_data[23] >> 4 & 0x01)
         << endl; */

    // Transponder Tuner
    int i;
    int digit_tuner[4];

    digit_tuner[0] = radio_switch_data[25] & 0x0f;
    digit_tuner[1] = ( radio_switch_data[25] >> 4 ) & 0x0f;
    digit_tuner[2] = radio_switch_data[29] & 0x0f;
    digit_tuner[3] = ( radio_switch_data[29] >> 4 ) & 0x0f;
    static bool first_time = true;
    static int last_digit_tuner[4];
    if ( first_time ) {
        first_time = false;
        for ( i = 0; i < 4; ++i ) {
            last_digit_tuner[i] = digit_tuner[i];
        }
    }

    int id_code = xpdr_id_code->getIntValue();
    int digit[4];
    int place = 1000;
    for ( i = 0; i < 4; ++i ) {
        digit[i] = id_code / place;
        id_code -= digit[i] * place;
        place /= 10;
    }

    for ( i = 0; i < 4; ++i ) {
        if ( digit_tuner[i] != last_digit_tuner[i] ) {
            diff = digit_tuner[i] - last_digit_tuner[i];
            if ( abs(diff) > 4 ) {
                // roll over
                if ( digit_tuner[i] < last_digit_tuner[i] ) {
                    // going up
                    diff = 15 - last_digit_tuner[i] + digit_tuner[i];
                } else {
                    // going down
                    diff = digit_tuner[i] - 15 - last_digit_tuner[i];
                }
            }
            digit[i] += diff;
        }
        while ( digit[i] >= 8 ) { digit[i] -= 8; }
        while ( digit[i] < 0 )  { digit[i] += 8; }
        last_digit_tuner[i] = digit_tuner[i];
    }

    fgSetInt( "/radios/kt-70/inputs/digit1", digit[0] );
    fgSetInt( "/radios/kt-70/inputs/digit2", digit[1] );
    fgSetInt( "/radios/kt-70/inputs/digit3", digit[2] );
    fgSetInt( "/radios/kt-70/inputs/digit4", digit[3] );

    int tmp = 0;
    for ( i = 0; i < 5; ++i ) {
        if ( radio_switch_data[27] >> i & 0x01 ) {
            tmp = i + 1;
        }
    }
    fgSetInt( "/radios/kt-70/inputs/func-knob", tmp );
    fgSetInt( "/radios/kt-70/inputs/ident-btn",
              !(radio_switch_data[27] >> 5 & 0x01) );

    return true;
}


/////////////////////////////////////////////////////////////////////
// Update the radio display 
/////////////////////////////////////////////////////////////////////

bool FGATC610x::do_radio_display() {

    char digits[10];
    int i;

    if ( dme_switch != 0 ) {
	// DME minutes
	float minutes = dme_min->getFloatValue();
	if ( minutes > 999 ) {
	    minutes = 999.0;
	}
	snprintf(digits, 7, "%03.0f", minutes);
	for ( i = 0; i < 6; ++i ) {
	    digits[i] -= '0';
	}
	radio_display_data[0] = digits[1] << 4 | digits[2];
	radio_display_data[1] = 0xf0 | digits[0];
	
	// DME knots
	float knots = dme_kt->getFloatValue();
	if ( knots > 999 ) {
	    knots = 999.0;
	}
	snprintf(digits, 7, "%03.0f", knots);
	for ( i = 0; i < 6; ++i ) {
	    digits[i] -= '0';
	}
	radio_display_data[2] = digits[1] << 4 | digits[2];
	radio_display_data[3] = 0xf0 | digits[0];

	// DME distance (nm)
	float nm = dme_nm->getFloatValue();
	if ( nm > 99 ) {
	    nm = 99.0;
	}
	snprintf(digits, 7, "%04.1f", nm);
	for ( i = 0; i < 6; ++i ) {
	    digits[i] -= '0';
	}
	radio_display_data[4] = digits[1] << 4 | digits[3];
	radio_display_data[5] = 0x00 | digits[0];
	// the 0x00 in the upper nibble of the 6th byte of each
	// display turns on the decimal point
    } else {
	// blank dem display
	for ( i = 0; i < 6; ++i ) {
	    radio_display_data[i] = 0xff;
	}
    }

    if ( navcom1_power->getBoolValue() ) {
        // Com1 standby frequency
        float com1_stby = com1_stby_freq->getFloatValue();
        if ( fabs(com1_stby) > 999.99 ) {
            com1_stby = 0.0;
        }
        snprintf(digits, 7, "%06.3f", com1_stby);
        for ( i = 0; i < 6; ++i ) {
            digits[i] -= '0';
        }
        radio_display_data[6] = digits[4] << 4 | digits[5];
        radio_display_data[7] = digits[1] << 4 | digits[2];
        radio_display_data[8] = 0xf0 | digits[0];

        // Com1 in use frequency
        float com1 = com1_freq->getFloatValue();
        if ( fabs(com1) > 999.99 ) {
            com1 = 0.0;
        }
        snprintf(digits, 7, "%06.3f", com1);
        for ( i = 0; i < 6; ++i ) {
            digits[i] -= '0';
        }
        radio_display_data[9] = digits[4] << 4 | digits[5];
        radio_display_data[10] = digits[1] << 4 | digits[2];
        radio_display_data[11] = 0x00 | digits[0];
        // the 0x00 in the upper nibble of the 6th byte of each display
        // turns on the decimal point
    } else {
        radio_display_data[6] = 0xff;
        radio_display_data[7] = 0xff;
        radio_display_data[8] = 0xff;
        radio_display_data[9] = 0xff;
        radio_display_data[10] = 0xff;
        radio_display_data[11] = 0xff;
    }

    if ( navcom2_power->getBoolValue() ) {
        // Com2 standby frequency
        float com2_stby = com2_stby_freq->getFloatValue();
        if ( fabs(com2_stby) > 999.99 ) {
            com2_stby = 0.0;
        }
        snprintf(digits, 7, "%06.3f", com2_stby);
        for ( i = 0; i < 6; ++i ) {
            digits[i] -= '0';
        }
        radio_display_data[18] = digits[4] << 4 | digits[5];
        radio_display_data[19] = digits[1] << 4 | digits[2];
        radio_display_data[20] = 0xf0 | digits[0];

        // Com2 in use frequency
        float com2 = com2_freq->getFloatValue();
        if ( fabs(com2) > 999.99 ) {
	com2 = 0.0;
        }
        snprintf(digits, 7, "%06.3f", com2);
        for ( i = 0; i < 6; ++i ) {
            digits[i] -= '0';
        }
        radio_display_data[21] = digits[4] << 4 | digits[5];
        radio_display_data[22] = digits[1] << 4 | digits[2];
        radio_display_data[23] = 0x00 | digits[0];
        // the 0x00 in the upper nibble of the 6th byte of each display
        // turns on the decimal point
    } else {
        radio_display_data[18] = 0xff;
        radio_display_data[19] = 0xff;
        radio_display_data[20] = 0xff;
        radio_display_data[21] = 0xff;
        radio_display_data[22] = 0xff;
        radio_display_data[23] = 0xff;
    }

    if ( navcom1_power->getBoolValue() ) {
        // Nav1 standby frequency
        float nav1_stby = nav1_stby_freq->getFloatValue();
        if ( fabs(nav1_stby) > 999.99 ) {
	nav1_stby = 0.0;
        }
        snprintf(digits, 7, "%06.2f", nav1_stby);
        for ( i = 0; i < 6; ++i ) {
            digits[i] -= '0';
        }
        radio_display_data[12] = digits[4] << 4 | digits[5];
        radio_display_data[13] = digits[1] << 4 | digits[2];
        radio_display_data[14] = 0xf0 | digits[0];

        // Nav1 in use frequency
        float nav1 = nav1_freq->getFloatValue();
        if ( fabs(nav1) > 999.99 ) {
            nav1 = 0.0;
        }
        snprintf(digits, 7, "%06.2f", nav1);
        for ( i = 0; i < 6; ++i ) {
            digits[i] -= '0';
        }
        radio_display_data[15] = digits[4] << 4 | digits[5];
        radio_display_data[16] = digits[1] << 4 | digits[2];
        radio_display_data[17] = 0x00 | digits[0];
        // the 0x00 in the upper nibble of the 6th byte of each display
        // turns on the decimal point
    } else {
        radio_display_data[12] = 0xff;
        radio_display_data[13] = 0xff;
        radio_display_data[14] = 0xff;
        radio_display_data[15] = 0xff;
        radio_display_data[16] = 0xff;
        radio_display_data[17] = 0xff;
    }

    if ( navcom2_power->getBoolValue() ) {
        // Nav2 standby frequency
        float nav2_stby = nav2_stby_freq->getFloatValue();
        if ( fabs(nav2_stby) > 999.99 ) {
            nav2_stby = 0.0;
        }
        snprintf(digits, 7, "%06.2f", nav2_stby);
        for ( i = 0; i < 6; ++i ) {
            digits[i] -= '0';
        }
        radio_display_data[24] = digits[4] << 4 | digits[5];
        radio_display_data[25] = digits[1] << 4 | digits[2];
        radio_display_data[26] = 0xf0 | digits[0];

        // Nav2 in use frequency
        float nav2 = nav2_freq->getFloatValue();
        if ( fabs(nav2) > 999.99 ) {
            nav2 = 0.0;
        }
        snprintf(digits, 7, "%06.2f", nav2);
        for ( i = 0; i < 6; ++i ) {
            digits[i] -= '0';
        }
        radio_display_data[27] = digits[4] << 4 | digits[5];
        radio_display_data[28] = digits[1] << 4 | digits[2];
        radio_display_data[29] = 0x00 | digits[0];
        // the 0x00 in the upper nibble of the 6th byte of each display
        // turns on the decimal point
    } else {
        radio_display_data[24] = 0xff;
        radio_display_data[25] = 0xff;
        radio_display_data[26] = 0xff;
        radio_display_data[27] = 0xff;
        radio_display_data[28] = 0xff;
        radio_display_data[29] = 0xff;
    }

    // ADF standby frequency / timer
    if ( adf_power->getBoolValue() ) {
        if ( adf_stby_mode->getIntValue() == 0 ) {
            // frequency
            float adf_stby = adf_stby_freq->getFloatValue();
            if ( fabs(adf_stby) > 1799 ) {
                adf_stby = 1799;
            }
            snprintf(digits, 7, "%04.0f", adf_stby);
            for ( i = 0; i < 6; ++i ) {
                digits[i] -= '0';
            }
            radio_display_data[30] = digits[3] << 4 | 0x0f;
            radio_display_data[31] = digits[1] << 4 | digits[2];
            if ( digits[0] == 0 ) {
                radio_display_data[32] = 0xff;
            } else {
                radio_display_data[32] = 0xf0 | digits[0];
            }
        } else {
            // timer
            double time;
            int hours, min, sec;
            if ( adf_timer_mode->getIntValue() == 0 ) {
                time = adf_flight_timer->getDoubleValue();
            } else {
                time = adf_elapsed_timer->getDoubleValue();
            }
            // cout << time << endl;
            hours = (int)(time / 3600.0);
            time -= hours * 3600.00;
            min = (int)(time / 60.0);
            time -= min * 60.0;
            sec = (int)time;
            int big, little;
            if ( hours > 0 ) {
                big = hours;
                if ( big > 99 ) {
                    big = 99;
                }
                little = min;
            } else {
                big = min;
                little = sec;
            }
            if ( big > 99 ) {
                big = 99;
            }
            // cout << big << ":" << little << endl;
            snprintf(digits, 7, "%02d%02d", big, little);
            for ( i = 0; i < 6; ++i ) {
                digits[i] -= '0';
            }
            radio_display_data[30] = digits[3] << 4 | 0x0f;
            radio_display_data[31] = digits[1] << 4 | digits[2];
            radio_display_data[32] = 0xf0 | digits[0];
        }

        // ADF in use frequency
        float adf = adf_freq->getFloatValue();
        if ( fabs(adf) > 1799 ) {
            adf = 1799;
        }
        snprintf(digits, 7, "%04.0f", adf);
        for ( i = 0; i < 6; ++i ) {
            digits[i] -= '0';
        }
        radio_display_data[33] = digits[2] << 4 | digits[3];
        if ( digits[0] == 0 ) {
            radio_display_data[34] = 0xf0 | digits[1];
        } else {
            radio_display_data[34] = digits[0] << 4 | digits[1];
        }
    } else {
        radio_display_data[30] = 0xff;
        radio_display_data[31] = 0xff;
        radio_display_data[32] = 0xff;
        radio_display_data[33] = 0xff;
        radio_display_data[34] = 0xff;
    }
    
    // Transponder code and flight level
    if ( xpdr_func_knob->getIntValue() == 2 ) {
        // test mode
        radio_display_data[36] = 8 << 4 | 8;
        radio_display_data[37] = 8 << 4 | 8;
        radio_display_data[38] = 0xff;
        radio_display_data[39] = 8 << 4 | 0x0f;
        radio_display_data[40] = 8 << 4 | 8;
    } else if ( xpdr_func_knob->getIntValue() > 0 ) {
        // other on modes
        int id_code = xpdr_id_code->getIntValue();
        int place = 1000;
        for ( i = 0; i < 4; ++i ) {
            digits[i] = id_code / place;
            id_code -= digits[i] * place;
            place /= 10;
        }
        radio_display_data[36] = digits[2] << 4 | digits[3];
        radio_display_data[37] = digits[0] << 4 | digits[1];
        radio_display_data[38] = 0xff;

        if ( xpdr_func_knob->getIntValue() == 3 ||
             xpdr_func_knob->getIntValue() == 5 )
        {
            // do flight level display
            snprintf(digits, 7, "%03d", xpdr_flight_level->getIntValue() );
            for ( i = 0; i < 6; ++i ) {
                digits[i] -= '0';
            }
           radio_display_data[39] = digits[2] << 4 | 0x0f;
           radio_display_data[40] = digits[0] << 4 | digits[1];
        } else {
            // blank flight level display
            radio_display_data[39] = 0xff;
            radio_display_data[40] = 0xff;
        }
    } else {
        // off
        radio_display_data[36] = 0xff;
        radio_display_data[37] = 0xff;
        radio_display_data[38] = 0xff;
        radio_display_data[39] = 0xff;
        radio_display_data[40] = 0xff;
    }

    ATC610xSetRadios( radios_fd, radio_display_data );

    return true;
}


/////////////////////////////////////////////////////////////////////
// Drive the stepper motors
/////////////////////////////////////////////////////////////////////

bool FGATC610x::do_steppers() {
    float diff = mag_compass->getFloatValue() - compass_position;
    while ( diff < -180.0 ) { diff += 360.0; }
    while ( diff >  180.0 ) { diff -= 360.0; }

    int steps = (int)(diff * 4);
    // cout << "steps = " << steps << endl;
    if ( steps > 4 ) { steps = 4; }
    if ( steps < -4 ) { steps = -4; }

    if ( abs(steps) > 0 ) {
	unsigned char cmd = 0x80;	// stepper command
	if ( steps > 0 ) {
	    cmd |= 0x20;		// go up
	} else {
	    cmd |= 0x00;		// go down
	}
	cmd |= abs(steps);

	// sync compass_position with hardware position
	compass_position += (float)steps / 4.0;

	ATC610xSetStepper( stepper_fd, ATC_COMPASS_CH, cmd );
    }

    return true;
}


/////////////////////////////////////////////////////////////////////
// Read the switch positions
/////////////////////////////////////////////////////////////////////

// decode the packed switch data
static void update_switch_matrix(
        int board,
	unsigned char switch_data[ATC_SWITCH_BYTES],
	int switch_matrix[2][ATC_NUM_COLS][ATC_SWITCH_BYTES] )
{
    for ( int row = 0; row < ATC_SWITCH_BYTES; ++row ) {
	unsigned char switches = switch_data[row];

	for( int column = 0; column < ATC_NUM_COLS; ++column ) {
	    switch_matrix[board][column][row] = switches & 1;
	    switches = switches >> 1;
	}			
    }
}                     

bool FGATC610x::do_switches() {
    ATC610xReadSwitches( switches_fd, switch_data );

    // unpack the switch data
    int switch_matrix[2][ATC_NUM_COLS][ATC_SWITCH_BYTES];
    update_switch_matrix( board, switch_data, switch_matrix );

    // magnetos and starter switch
    int magnetos = 0;
    bool starter = false;
    if ( switch_matrix[board][3][1] == 1 ) {
	magnetos = 3;
	starter = true;
    } else if ( switch_matrix[board][2][1] == 1 ) {
	magnetos = 3;
	starter = false;
    } else if ( switch_matrix[board][1][1] == 1 ) {
	magnetos = 2;
	starter = false;
    } else if ( switch_matrix[board][0][1] == 1 ) {
	magnetos = 1;
	starter = false;
    } else {
	magnetos = 0;
	starter = false;
    }

    // do a bit of filtering on the magneto/starter switch and the
    // flap lever because these are not well debounced in hardware
    static int mag1, mag2, mag3;
    mag3 = mag2;
    mag2 = mag1;
    mag1 = magnetos;
    if ( mag1 == mag2 && mag2 == mag3 ) {
        fgSetInt( "/controls/magnetos[0]", magnetos );
    }
    static bool start1, start2, start3;
    start3 = start2;
    start2 = start1;
    start1 = starter;
    if ( start1 == start2 && start2 == start3 ) {
        fgSetBool( "/controls/starter[0]", starter );
    }

    // flaps
    float flaps = 0.0;
    if ( switch_matrix[board][6][3] ) {
	flaps = 1.0;
    } else if ( switch_matrix[board][5][3] ) {
	flaps = 2.0 / 3.0;
    } else if ( switch_matrix[board][4][3] ) {
	flaps = 1.0 / 3.0;
    } else if ( !switch_matrix[board][4][3] ) {
	flaps = 0.0;
    }

    // do a bit of filtering on the magneto/starter switch and the
    // flap lever because these are not well debounced in hardware
    static float flap1, flap2, flap3;
    flap3 = flap2;
    flap2 = flap1;
    flap1 = flaps;
    if ( flap1 == flap2 && flap2 == flap3 ) {
        fgSetFloat( "/controls/flaps", flaps );
    }

    // fuel selector (also filtered)
    int fuel = 0;
    if ( switch_matrix[board][2][3] ) {
        // both
        fuel = 3;
    } else if ( switch_matrix[board][1][3] ) {
        // left
        fuel = 1;
    } else if ( switch_matrix[board][3][3] ) {
        // right
        fuel = 2;
    } else {
        // fuel cutoff
        fuel = 0;
    }

    static int fuel1, fuel2, fuel3;
    fuel3 = fuel2;
    fuel2 = fuel1;
    fuel1 = fuel;
    if ( fuel1 == fuel2 && fuel2 == fuel3 ) {
        fgSetBool( "/controls/fuel-selector[0]", (fuel & 0x01) > 0 );
        fgSetBool( "/controls/fuel-selector[1]", (fuel & 0x02) > 0 );
    }

    return true;
}


bool FGATC610x::process() {
    // Lock the hardware, skip if it's not ready yet
    if ( ATC610xLock( lock_fd ) > 0 ) {

	do_analog_in();
	do_lights();
	do_radio_switches();
	do_radio_display();
	do_steppers();
	do_switches();
	
	ATC610xRelease( lock_fd );

	return true;
    } else {
	return false;
    }
}


bool FGATC610x::close() {

    return true;
}