I am currently using FGFS 0.9.10 and trying to interface flightgear with
external fdm data from a program in C.I tested the interfacing using a
sample program.I found that Flightgear responds to the data generated by
external fdm program, however not smoothly i.e. there is no smooth movement
of aircraft.
When I send the packets every 1 ms, the log-level entry in the command
windows shows"Sucess reading data".However the FGFS graphical screen freezes
and the aircraft doesn't move.But when I disable the internet connection
temporarily,it responds momentarily.It means that FGFS is responding to
packets.
I am using this command to invoke flightgear:
cd C:\FlightGear\bin\Win32\
FGFS.EXE --native-fdm=socket,in,30,,5500,udp --fdm=external
--log-level=debug --timeofday=noon --disable-random-objects.
If someone has any related information of sucessful interface of external
fdm with Flightgear then please help......
The sample program which I am using is:
#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>
const uint32_t FG_NET_FDM_VERSION = 24;
int fgfs_port=5500;
char* fgfs_ip="10.101.13.41";
#define D2R (3.14159 / 180.0)
#define FG_MAX_ENGINES 4
#define FG_MAX_WHEELS 3
#define FG_MAX_TANKS 4
int update_period=1;
int sendSocket;
void run();
struct sockaddr_in serv_addr;
typedef struct {
/* enum {
FG_MAX_ENGINES = 4,
FG_MAX_WHEELS = 3,
FG_MAX_TANKS = 4
};*/
uint32_t version; // increment when data values change
uint32_t padding; // padding
// Positions
double longitude; // geodetic (radians)
double latitude; // geodetic (radians)
double altitude; // above sea level (meters)
float agl; // above ground level (meters)
float phi; // roll (radians)
float theta; // pitch (radians)
float psi; // yaw or true heading (radians)
float alpha; // angle of attack (radians)
float beta; // side slip angle (radians)
// Velocities
float phidot; // roll rate (radians/sec)
float thetadot; // pitch rate (radians/sec)
float psidot; // yaw rate (radians/sec)
float vcas; // calibrated airspeed
float climb_rate; // feet per second
float v_north; // north velocity in local/body frame, fps
float v_east; // east velocity in local/body frame, fps
float v_down; // down/vertical velocity in local/body
frame, fps
float v_wind_body_north; // north velocity in local/body frame
// relative to local airmass, fps
float v_wind_body_east; // east velocity in local/body frame
// relative to local airmass, fps
float v_wind_body_down; // down/vertical velocity in local/body
// frame relative to local airmass, fps
// Accelerations
float A_X_pilot; // X accel in body frame ft/sec^2
float A_Y_pilot; // Y accel in body frame ft/sec^2
float A_Z_pilot; // Z accel in body frame ft/sec^2
// Stall
float stall_warning; // 0.0 - 1.0 indicating the amount of stall
float slip_deg; // slip ball deflection
// Pressure
// Engine status
uint32_t num_engines; // Number of valid engines
uint32_t eng_state[FG_MAX_ENGINES];// Engine state (off, cranking,
running)
float rpm[FG_MAX_ENGINES]; // Engine RPM rev/min
float fuel_flow[FG_MAX_ENGINES]; // Fuel flow gallons/hr
float fuel_px[FG_MAX_ENGINES]; // Fuel pressure psi
float egt[FG_MAX_ENGINES]; // Exhuast gas temp deg F
float cht[FG_MAX_ENGINES]; // Cylinder head temp deg F
float mp_osi[FG_MAX_ENGINES]; // Manifold pressure
float tit[FG_MAX_ENGINES]; // Turbine Inlet Temperature
float oil_temp[FG_MAX_ENGINES]; // Oil temp deg F
float oil_px[FG_MAX_ENGINES]; // Oil pressure psi
// Consumables
uint32_t num_tanks; // Max number of fuel tanks
float fuel_quantity[FG_MAX_TANKS];
// Gear status
uint32_t num_wheels;
uint32_t wow[FG_MAX_WHEELS];
float gear_pos[FG_MAX_WHEELS];
float gear_steer[FG_MAX_WHEELS];
float gear_compression[FG_MAX_WHEELS];
// Environment
uint32_t cur_time; // current unix time
// FIXME: make this uint64_t before 2038
int32_t warp; // offset in seconds to unix time
float visibility; // visibility in meters (for env. effects)
// Control surface positions (normalized values)
float elevator;
float elevator_trim_tab;
float left_flap;
float right_flap;
float left_aileron;
float right_aileron;
float rudder;
float nose_wheel;
float speedbrake;
float spoilers;
} fdm_data;
int net_init(void)
{
int s;
struct sockaddr_in cli_addr;
s = socket(AF_INET, SOCK_DGRAM, 0);
bzero((char *)&cli_addr, sizeof(cli_addr));
cli_addr.sin_family = AF_INET;
cli_addr.sin_addr.s_addr = htonl(INADDR_ANY);
cli_addr.sin_port = htons(INADDR_ANY);
bind(s, (struct sockaddr *)&cli_addr, sizeof(cli_addr));
return s;
}
double htond (double x)
{
int * p = (int*)&x;
int tmp = p[0];
p[0] = htonl(p[1]);
p[1] = htonl(tmp);
return x;
}
float htonf (float x)
{
int * p = (int *)&x;
*p = htonl(*p);
return x;
}
int main(void)
{
int s;
s=net_init();
sendSocket=s;
// printf("Socket no=%d",s);
// struct sockaddr_in serv_addr;
bzero((char *)&serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = inet_addr(fgfs_ip);
serv_addr.sin_port = htons(fgfs_port);
if (s!= -1)
{ run();}
else
printf("\nSocket creation failed");
return 0;
}
void run()
{
double latitude = 0.59823; // degs
double longitude = 0.69202; // degs
double altitude = 300.0; // meters above sea level
double lat,lon;
float roll = 0.0; // degs
float pitch = 0.0; // degs
float yaw = 0.0; // degs
float visibility = 5000.0; // meters
static int flag = 1;
fdm_data fdm;
while (1)
{
sleep(update_period);
// fdm_data fdm;
memset(&fdm,0,sizeof(fdm));
fdm.version = htonl(FG_NET_FDM_VERSION);
// fdm.latitude = htond(latitude * D2R);
// fdm.longitude = htond(longitude * D2R);
fdm.altitude = htond(altitude);
fdm.phi = htonf(roll * D2R);
fdm.theta = htonf(pitch * D2R);
fdm.psi = htonf(yaw * D2R);
fdm.num_engines = htonl(1);
fdm.num_tanks = htonl(1);
fdm.fuel_quantity[0] = htonf(100.0);
fdm.num_wheels = htonl(3);
fdm.cur_time = htonl(time(0));
fdm.warp = htonl(1);
fdm.visibility = htonf(visibility);
// sendto(sendSocket,(char *)&fdm,sizeof(fdm),0,(struct sockaddr
*)&serv_addr,sizeof(serv_addr));
//static bool flag = true;
/* if (flag)
{
roll += 5.0;
}
else
{
roll -= 5.0;
}
flag = !flag;*/
latitude=latitude+0.0000001;
longitude=longitude+0.0000001;
if(latitude<90)
fdm.latitude=htond(latitude*D2R);
if(longitude<180)
fdm.longitude=htond(longitude*D2R);
if (latitude>=90)
{
lat=180-latitude;
fdm.latitude=htond(lat*D2R);
}
if (longitude>=180)
{
lon=360-longitude;
fdm.longitude=htond(lon*D2R);
}
if(latitude>=180)
{ latitude=0;
fdm.latitude=htond(0.00);
}
if(longitude>=360)
{
longitude=0;
fdm.longitude=htond(0.00);
}
sendto(sendSocket,(char *)&fdm,sizeof(fdm),0,(struct sockaddr
*)&serv_addr,sizeof(serv_addr));
}
}
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