/*
* @file attitude_estimator_so3_comp_main.c
*
* Nonlinear SO3 filter for Attitude Estimation.
*/
#include <nuttx/config.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <stdbool.h>
#include <poll.h>
#include <fcntl.h>
#include <float.h>
#include <nuttx/sched.h>
#include <sys/prctl.h>
#include <termios.h>
#include <errno.h>
#include <limits.h>
#include <math.h>
#include <uORB/uORB.h>
#include <uORB/topics/debug_key_value.h>
#include <uORB/topics/sensor_combined.h>
#include <uORB/topics/vehicle_attitude.h>
#include <uORB/topics/vehicle_status.h>
#include <uORB/topics/parameter_update.h>
#include <drivers/drv_hrt.h>
#include <systemlib/systemlib.h>
#include <systemlib/perf_counter.h>
#include <systemlib/err.h>
#ifdef __cplusplus
extern "C" {
#endif
#include "attitude_estimator_so3_comp_params.h"
#ifdef __cplusplus
}
#endif
extern "C" __EXPORT int attitude_estimator_so3_comp_main(int argc, char *argv[]);
static bool thread_should_exit = false; /**< Deamon exit flag */
static bool thread_running = false; /**< Deamon status flag */
static int attitude_estimator_so3_comp_task; /**< Handle of deamon task / thread */
static float q0 = 1.0f, q1 = 0.0f, q2 = 0.0f, q3 = 0.0f; /** quaternion of sensor frame relative to auxiliary frame */
static float gyro_bias[3] = {0.0f, 0.0f, 0.0f}; /** bias estimation */
static float gravity_vector[3] = {0.0f,0.0f,0.0f}; /** estimated gravity vector */
//! Serial packet related
static int uart;
static int baudrate;
/**
* Mainloop of attitude_estimator_so3_comp.
*/
int attitude_estimator_so3_comp_thread_main(int argc, char *argv[]);
/**
* Print the correct usage.
*/
static void usage(const char *reason);
static void
usage(const char *reason)
{
if (reason)
fprintf(stderr, "%s\n", reason);
fprintf(stderr, "usage: attitude_estimator_so3_comp {start|stop|status} [-d <devicename>] [-b <baud rate>]\n"
"-d and -b options are for separate visualization with raw data (quaternion packet) transfer\n"
"ex) attitude_estimator_so3_comp start -d /dev/ttyS1 -b 115200\n");
exit(1);
}
/**
* The attitude_estimator_so3_comp app only briefly exists to start
* the background job. The stack size assigned in the
* Makefile does only apply to this management task.
*
* The actual stack size should be set in the call
* to task_create().
*/
int attitude_estimator_so3_comp_main(int argc, char *argv[])
{
if (argc < 1)
usage("missing command");
if (!strcmp(argv[1], "start")) {
if (thread_running) {
printf("attitude_estimator_so3_comp already running\n");
/* this is not an error */
exit(0);
}
thread_should_exit = false;
attitude_estimator_so3_comp_task = task_spawn("attitude_estimator_so3_comp",
SCHED_DEFAULT,
SCHED_PRIORITY_MAX - 5,
12400,
attitude_estimator_so3_comp_thread_main,
(const char **)argv);
exit(0);
}
if (!strcmp(argv[1], "stop")) {
thread_should_exit = true;
while(thread_running){
usleep(200000);
printf(".");
}
printf("terminated.");
exit(0);
}
if (!strcmp(argv[1], "status")) {
if (thread_running) {
printf("\tattitude_estimator_so3_comp app is running\n");
} else {
printf("\tattitude_estimator_so3_comp app not started\n");
}
exit(0);
}
usage("unrecognized command");
exit(1);
}
//---------------------------------------------------------------------------------------------------
// Fast inverse square-root
// See: http://en.wikipedia.org/wiki/Fast_inverse_square_root
float invSqrt(float number) {
volatile long i;
volatile float x, y;
volatile const float f = 1.5F;
x = number * 0.5F;
y = number;
i = * (( long * ) &y);
i = 0x5f375a86 - ( i >> 1 );
y = * (( float * ) &i);
y = y * ( f - ( x * y * y ) );
return y;
}
void MahonyAHRSupdate(float gx, float gy, float gz, float ax, float ay, float az, float mx, float my, float mz, float twoKp, float twoKi, float dt) {
float recipNorm;
float q0q0, q0q1, q0q2, q0q3, q1q1, q1q2, q1q3, q2q2, q2q3, q3q3;
float halfex = 0.0f, halfey = 0.0f, halfez = 0.0f;
// Auxiliary variables to avoid repeated arithmetic
q0q0 = q0 * q0;
q0q1 = q0 * q1;
q0q2 = q0 * q2;
q0q3 = q0 * q3;
q1q1 = q1 * q1;
q1q2 = q1 * q2;
q1q3 = q1 * q3;
q2q2 = q2 * q2;
q2q3 = q2 * q3;
q3q3 = q3 * q3;
//! If magnetometer measurement is available, use it.
if((mx == 0.0f) && (my == 0.0f) && (mz == 0.0f)) {
float hx, hy, bx, bz;
float halfwx, halfwy, halfwz;
// Normalise magnetometer measurement
recipNorm = invSqrt(mx * mx + my * my + mz * mz);
mx *= recipNorm;
my *= recipNorm;
mz *= recipNorm;
// Reference direction of Earth's magnetic field
hx = 2.0f * (mx * (0.5f - q2q2 - q3q3) + my * (q1q2 - q0q3) + mz * (q1q3 + q0q2));
hy = 2.0f * (mx * (q1q2 + q0q3) + my * (0.5f - q1q1 - q3q3) + mz * (q2q3 - q0q1));
bx = sqrt(hx * hx + hy * hy);
bz = 2.0f * (mx * (q1q3 - q0q2) + my * (q2q3 + q0q1) + mz * (0.5f - q1q1 - q2q2));
// Estimated direction of magnetic field
halfwx = bx * (0.5f - q2q2 - q3q3) + bz * (q1q3 - q0q2);
halfwy = bx * (q1q2 - q0q3) + bz * (q0q1 + q2q3);
halfwz = bx * (q0q2 + q1q3) + bz * (0.5f - q1q1 - q2q2);
// Error is sum of cross product between estimated direction and measured direction of field vectors
halfex += (my * halfwz - mz * halfwy);
halfey += (mz * halfwx - mx * halfwz);
halfez += (mx * halfwy - my * halfwx);
}
// Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation)
if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) {
float halfvx, halfvy, halfvz;
// Normalise accelerometer measurement
recipNorm = invSqrt(ax * ax + ay * ay + az * az);
ax *= recipNorm;
ay *= recipNorm;
az *= recipNorm;
// Estimated direction of gravity and magnetic field
halfvx = q1q3 - q0q2;
halfvy = q0q1 + q2q3;
halfvz = q0q0 - 0.5f + q3q3;
// Error is sum of cross product between estimated direction and measured direction of field vectors
halfex += ay * halfvz - az * halfvy;
halfey += az * halfvx - ax * halfvz;
halfez += ax * halfvy - ay * halfvx;
}
// Apply feedback only when valid data has been gathered from the accelerometer or magnetometer
if(halfex != 0.0f && halfey != 0.0f && halfez != 0.0f) {
// Compute and apply integral feedback if enabled
if(twoKi > 0.0f) {
gyro_bias[0] += twoKi * halfex * dt; // integral error scaled by Ki
gyro_bias[1] += twoKi * halfey * dt;
gyro_bias[2] += twoKi * halfez * dt;
gx += gyro_bias[0]; // apply integral feedback
gy += gyro_bias[1];
gz += gyro_bias[2];
}
else {
gyro_bias[0] = 0.0f; // prevent integral windup
gyro_bias[1] = 0.0f;
gyro_bias[2] = 0.0f;
}
// Apply proportional feedback
gx += twoKp * halfex;
gy += twoKp * halfey;
gz += twoKp * halfez;
}
// Integrate rate of change of quaternion
gx *= (0.5f * dt); // pre-multiply common factors
gy *= (0.5f * dt);
gz *= (0.5f * dt);
q0 +=(-q1 * gx - q2 * gy - q3 * gz);
q1 += (q0 * gx + q2 * gz - q3 * gy);
q2 += (q0 * gy - q1 * gz + q3 * gx);
q3 += (q0 * gz + q1 * gy - q2 * gx);
// Normalise quaternion
recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3);
q0 *= recipNorm;
q1 *= recipNorm;
q2 *= recipNorm;
q3 *= recipNorm;
}
void send_uart_byte(char c)
{
write(uart,&c,1);
}
void send_uart_bytes(uint8_t *data, int length)
{
write(uart,data,(size_t)(sizeof(uint8_t)*length));
}
void send_uart_float(float f) {
uint8_t * b = (uint8_t *) &f;
//! Assume float is 4-bytes
for(int i=0; i<4; i++) {
uint8_t b1 = (b[i] >> 4) & 0x0f;
uint8_t b2 = (b[i] & 0x0f);
uint8_t c1 = (b1 < 10) ? ('0' + b1) : 'A' + b1 - 10;
uint8_t c2 = (b2 < 10) ? ('0' + b2) : 'A' + b2 - 10;
send_uart_bytes(&c1,1);
send_uart_bytes(&c2,1);
}
}
void send_uart_float_arr(float *arr, int length)
{
for(int i=0;i<length;++i)
{
send_uart_float(arr[i]);
send_uart_byte(',');
}
}
int open_uart(int baud, const char *uart_name, struct termios *uart_config_original, bool *is_usb)
{
int speed;
switch (baud) {
case 0: speed = B0; break;
case 50: speed = B50; break;
case 75: speed = B75; break;
case 110: speed = B110; break;
case 134: speed = B134; break;
case 150: speed = B150; break;
case 200: speed = B200; break;
case 300: speed = B300; break;
case 600: speed = B600; break;
case 1200: speed = B1200; break;
case 1800: speed = B1800; break;
case 2400: speed = B2400; break;
case 4800: speed = B4800; break;
case 9600: speed = B9600; break;
case 19200: speed = B19200; break;
case 38400: speed = B38400; break;
case 57600: speed = B57600; break;
case 115200: speed = B115200; break;
case 230400: speed = B230400; break;
case 460800: speed = B460800; break;
case 921600: speed = B921600; break;
default:
printf("ERROR: Unsupported baudrate: %d\n\tsupported examples:\n\n\t9600\n19200\n38400\n57600\n115200\n230400\n460800\n921600\n\n", baud);
return -EINVAL;
}
printf("[so3_comp_filt] UART is %s, baudrate is %d\n", uart_name, baud);
uart = open(uart_name, O_RDWR | O_NOCTTY);
/* Try to set baud rate */
struct termios uart_config;
int termios_state;
*is_usb = false;
/* make some wild guesses including that USB serial is indicated by either /dev/ttyACM0 or /dev/console */
if (strcmp(uart_name, "/dev/ttyACM0") != OK && strcmp(uart_name, "/dev/console") != OK) {
/* Back up the original uart configuration to restore it after exit */
if ((termios_state = tcgetattr(uart, uart_config_original)) < 0) {
printf("ERROR getting baudrate / termios config for %s: %d\n", uart_name, termios_state);
close(uart);
return -1;
}
/* Fill the struct for the new configuration */
tcgetattr(uart, &uart_config);
/* Clear ONLCR flag (which appends a CR for every LF) */
uart_config.c_oflag &= ~ONLCR;
/* Set baud rate */
if (cfsetispeed(&uart_config, speed) < 0 || cfsetospeed(&uart_config, speed) < 0) {
printf("ERROR setting baudrate / termios config for %s: %d (cfsetispeed, cfsetospeed)\n", uart_name, termios_state);
close(uart);
return -1;
}
if ((termios_state = tcsetattr(uart, TCSANOW, &uart_config)) < 0) {
printf("ERROR setting baudrate / termios config for %s (tcsetattr)\n", uart_name);
close(uart);
return -1;
}
} else {
*is_usb = true;
}
return uart;
}
/*
* [Rot_matrix,x_aposteriori,P_aposteriori] = attitudeKalmanfilter(dt,z_k,x_aposteriori_k,P_aposteriori_k,knownConst)
*/
/*
* EKF Attitude Estimator main function.
*
* Estimates the attitude recursively once started.
*
* @param argc number of commandline arguments (plus command name)
* @param argv strings containing the arguments
*/
int attitude_estimator_so3_comp_thread_main(int argc, char *argv[])
{
const unsigned int loop_interval_alarm = 6500; // loop interval in microseconds
//! Serial debug related
int ch;
struct termios uart_config_original;
bool usb_uart;
bool debug_mode = false;
char *device_name = "/dev/ttyS2";
baudrate = 115200;
//! Time constant
float dt = 0.005f;
/* output euler angles */
float euler[3] = {0.0f, 0.0f, 0.0f};
float Rot_matrix[9] = {1.f, 0, 0,
0, 1.f, 0,
0, 0, 1.f
}; /**< init: identity matrix */
float acc[3] = {0.0f, 0.0f, 0.0f};
float gyro[3] = {0.0f, 0.0f, 0.0f};
float mag[3] = {0.0f, 0.0f, 0.0f};
/* work around some stupidity in task_create's argv handling */
argc -= 2;
argv += 2;
//! -d <device_name>, default : /dev/ttyS2
//! -b <baud_rate>, default : 115200
while ((ch = getopt(argc,argv,"d:b:")) != EOF){
switch(ch){
case 'b':
baudrate = strtoul(optarg, NULL, 10);
if(baudrate == 0)
printf("invalid baud rate '%s'",optarg);
break;
case 'd':
device_name = optarg;
debug_mode = true;
break;
default:
usage("invalid argument");
}
}
if(debug_mode){
printf("Opening debugging port for 3D visualization\n");
uart = open_uart(baudrate, device_name, &uart_config_original, &usb_uart);
if (uart < 0)
printf("could not open %s", device_name);
else
printf("Open port success\n");
}
// print text
printf("Nonlinear SO3 Attitude Estimator initialized..\n\n");
fflush(stdout);
int overloadcounter = 19;
/* store start time to guard against too slow update rates */
uint64_t last_run = hrt_absolute_time();
struct sensor_combined_s raw;
memset(&raw, 0, sizeof(raw));
struct vehicle_attitude_s att;
memset(&att, 0, sizeof(att));
struct vehicle_status_s state;
memset(&state, 0, sizeof(state));
uint64_t last_data = 0;
uint64_t last_measurement = 0;
/* subscribe to raw data */
int sub_raw = orb_subscribe(ORB_ID(sensor_combined));
/* rate-limit raw data updates to 200Hz */
orb_set_interval(sub_raw, 4);
/* subscribe to param changes */
int sub_params = orb_subscribe(ORB_ID(parameter_update));
/* subscribe to system state*/
int sub_state = orb_subscribe(ORB_ID(vehicle_status));
/* advertise attitude */
orb_advert_t pub_att = orb_advertise(ORB_ID(vehicle_attitude), &att);
int loopcounter = 0;
int printcounter = 0;
thread_running = true;
/* advertise debug value */
// struct debug_key_value_s dbg = { .key = "", .value = 0.0f };
// orb_advert_t pub_dbg = -1;
float sensor_update_hz[3] = {0.0f, 0.0f, 0.0f};
// XXX write this out to perf regs
/* keep track of sensor updates */
uint32_t sensor_last_count[3] = {0, 0, 0};
uint64_t sensor_last_timestamp[3] = {0, 0, 0};
struct attitude_estimator_so3_comp_params so3_comp_params;
struct attitude_estimator_so3_comp_param_handles so3_comp_param_handles;
/* initialize parameter handles */
parameters_init(&so3_comp_param_handles);
uint64_t start_time = hrt_absolute_time();
bool initialized = false;
float gyro_offsets[3] = { 0.0f, 0.0f, 0.0f };
unsigned offset_count = 0;
/* register the perf counter */
perf_counter_t so3_comp_loop_perf = perf_alloc(PC_ELAPSED, "attitude_estimator_so3_comp");
/* Main loop*/
while (!thread_should_exit) {
struct pollfd fds[2];
fds[0].fd = sub_raw;
fds[0].events = POLLIN;
fds[1].fd = sub_params;
fds[1].events = POLLIN;
int ret = poll(fds, 2, 1000);
if (ret < 0) {
/* XXX this is seriously bad - should be an emergency */
} else if (ret == 0) {
/* check if we're in HIL - not getting sensor data is fine then */
orb_copy(ORB_ID(vehicle_status), sub_state, &state);
if (!state.flag_hil_enabled) {
fprintf(stderr,
"[att so3_comp] WARNING: Not getting sensors - sensor app running?\n");
}
} else {
/* only update parameters if they changed */
if (fds[1].revents & POLLIN) {
/* read from param to clear updated flag */
struct parameter_update_s update;
orb_copy(ORB_ID(parameter_update), sub_params, &update);
/* update parameters */
parameters_update(&so3_comp_param_handles, &so3_comp_params);
}
/* only run filter if sensor values changed */
if (fds[0].revents & POLLIN) {
/* get latest measurements */
orb_copy(ORB_ID(sensor_combined), sub_raw, &raw);
if (!initialized) {
gyro_offsets[0] += raw.gyro_rad_s[0];
gyro_offsets[1] += raw.gyro_rad_s[1];
gyro_offsets[2] += raw.gyro_rad_s[2];
offset_count++;
if (hrt_absolute_time() - start_time > 3000000LL) {
initialized = true;
gyro_offsets[0] /= offset_count;
gyro_offsets[1] /= offset_count;
gyro_offsets[2] /= offset_count;
}
} else {
perf_begin(so3_comp_loop_perf);
/* Calculate data time difference in seconds */
dt = (raw.timestamp - last_measurement) / 1000000.0f;
last_measurement = raw.timestamp;
uint8_t update_vect[3] = {0, 0, 0};
/* Fill in gyro measurements */
if (sensor_last_count[0] != raw.gyro_counter) {
update_vect[0] = 1;
sensor_last_count[0] = raw.gyro_counter;
sensor_update_hz[0] = 1e6f / (raw.timestamp - sensor_last_timestamp[0]);
sensor_last_timestamp[0] = raw.timestamp;
}
gyro[0] = raw.gyro_rad_s[0] - gyro_offsets[0];
gyro[1] = raw.gyro_rad_s[1] - gyro_offsets[1];
gyro[2] = raw.gyro_rad_s[2] - gyro_offsets[2];
/* update accelerometer measurements */
if (sensor_last_count[1] != raw.accelerometer_counter) {
update_vect[1] = 1;
sensor_last_count[1] = raw.accelerometer_counter;
sensor_update_hz[1] = 1e6f / (raw.timestamp - sensor_last_timestamp[1]);
sensor_last_timestamp[1] = raw.timestamp;
}
acc[0] = raw.accelerometer_m_s2[0];
acc[1] = raw.accelerometer_m_s2[1];
acc[2] = raw.accelerometer_m_s2[2];
/* update magnetometer measurements */
if (sensor_last_count[2] != raw.magnetometer_counter) {
update_vect[2] = 1;
sensor_last_count[2] = raw.magnetometer_counter;
sensor_update_hz[2] = 1e6f / (raw.timestamp - sensor_last_timestamp[2]);
sensor_last_timestamp[2] = raw.timestamp;
}
mag[0] = raw.magnetometer_ga[0];
mag[1] = raw.magnetometer_ga[1];
mag[2] = raw.magnetometer_ga[2];
uint64_t now = hrt_absolute_time();
unsigned int time_elapsed = now - last_run;
last_run = now;
if (time_elapsed > loop_interval_alarm) {
//TODO: add warning, cpu overload here
// if (overloadcounter == 20) {
// printf("CPU OVERLOAD DETECTED IN ATTITUDE ESTIMATOR EKF (%lu > %lu)\n", time_elapsed, loop_interval_alarm);
// overloadcounter = 0;
// }
overloadcounter++;
}
static bool const_initialized = false;
/* initialize with good values once we have a reasonable dt estimate */
if (!const_initialized && dt < 0.05f && dt > 0.005f) {
dt = 0.005f;
parameters_update(&so3_comp_param_handles, &so3_comp_params);
const_initialized = true;
}
/* do not execute the filter if not initialized */
if (!const_initialized) {
continue;
}
uint64_t timing_start = hrt_absolute_time();
MahonyAHRSupdate(gyro[0],gyro[1],gyro[2],acc[0],acc[1],acc[2],mag[0],mag[1],mag[2],so3_comp_params.Kp,so3_comp_params.Ki, dt);
float aSq = q0*q0; // 1
float bSq = q1*q1; // 2
float cSq = q2*q2; // 3
float dSq = q3*q3; // 4
float a = q0;
float b = q1;
float c = q2;
float d = q3;
Rot_matrix[0] = 2*aSq - 1 + 2*bSq; // 11
//Rot_matrix[1] = 2.0 * (b * c - a * d); // 12
//Rot_matrix[2] = 2.0 * (a * c + b * d); // 13
Rot_matrix[3] = 2.0 * (b * c - a * d); // 21
//Rot_matrix[4] = aSq - bSq + cSq - dSq; // 22
//Rot_matrix[5] = 2.0 * (c * d - a * b); // 23
Rot_matrix[6] = 2.0 * (b * d + a * c); // 31
Rot_matrix[7] = 2.0 * (c * d - a * b); // 32
Rot_matrix[8] = 2*aSq - 1 + 2*dSq; // 33
gravity_vector[0] = 2*(q1*q3-q0*q2);
gravity_vector[1] = 2*(q0*q1+q2*q3);
gravity_vector[2] = aSq - bSq - cSq + dSq;
//euler[0] = atan2f(Rot_matrix[7], Rot_matrix[8]);
//euler[1] = -asinf(Rot_matrix[6]);
//euler[2] = atan2f(Rot_matrix[3],Rot_matrix[0]);
// Euler angle directly from quaternion.
euler[0] = -atan2f(gravity_vector[1], sqrtf(gravity_vector[0]*gravity_vector[0] + gravity_vector[2]*gravity_vector[2])); // roll
euler[1] = atan2f(gravity_vector[0], sqrtf(gravity_vector[1]*gravity_vector[1] + gravity_vector[2]*gravity_vector[2])); // pitch
euler[2] = -atan2f(2*(q1*q2-q0*q3),2*(q0*q0+q1*q1)-1); // yaw
//euler[2] = atan2(2 * q1*q2 - 2 * q0*q3, 2 * q0*q0 + 2 * q1*q1 - 1); // psi
//euler[1] = -asin(2 * q1*q3 + 2 * q0*q2); // theta
//euler[0] = atan2(2 * q2*q3 - 2 * q0*q1, 2 * q0*q0 + 2 * q3*q3 - 1); // phi
/* swap values for next iteration, check for fatal inputs */
if (isfinite(euler[0]) && isfinite(euler[1]) && isfinite(euler[2])) {
/* Do something */
} else {
/* due to inputs or numerical failure the output is invalid, skip it */
continue;
}
if (last_data > 0 && raw.timestamp - last_data > 12000) printf("[attitude estimator so3_comp] sensor data missed! (%llu)\n", raw.timestamp - last_data);
last_data = raw.timestamp;
/* send out */
att.timestamp = raw.timestamp;
// XXX Apply the same transformation to the rotation matrix
att.roll = euler[0] - so3_comp_params.roll_off;
att.pitch = euler[1] - so3_comp_params.pitch_off;
att.yaw = euler[2] - so3_comp_params.yaw_off;
/* FIXME : This can be a problem for rate controller. Rate in body or inertial? */
att.rollspeed = gyro[0];
att.pitchspeed = gyro[1];
att.yawspeed = gyro[2];
att.rollacc = 0;
att.pitchacc = 0;
att.yawacc = 0;
/* TODO: Bias estimation required */
memcpy(&att.rate_offsets, &(gyro_bias), sizeof(att.rate_offsets));
/* copy rotation matrix */
memcpy(&att.R, Rot_matrix, sizeof(Rot_matrix));
att.R_valid = true;
if (isfinite(att.roll) && isfinite(att.pitch) && isfinite(att.yaw)) {
// Broadcast
orb_publish(ORB_ID(vehicle_attitude), pub_att, &att);
} else {
warnx("NaN in roll/pitch/yaw estimate!");
}
perf_end(so3_comp_loop_perf);
//! This will print out debug packet to visualization software
if(debug_mode)
{
float quat[4];
quat[0] = q0;
quat[1] = q1;
quat[2] = q2;
quat[3] = q3;
send_uart_float_arr(quat,4);
send_uart_byte('\n');
}
}
}
}
loopcounter++;
}// while
thread_running = false;
/* Reset the UART flags to original state */
if (!usb_uart)
tcsetattr(uart, TCSANOW, &uart_config_original);
return 0;
}