pmsm-control/test_sw/main_pmsm.c

   1 /**
   2  * \file main_pmsm.c
   3  * \author Martin Prudek
   4  * \brief Mainfile pro pmsm control.
   5  */
   6
   7 #ifndef NULL
   8 #define NULL (void*) 0
   9 #endif /*NULL*/
  10
  11
  12 #include <stdlib.h>     /*exit*/
  13 #include <signal.h>     /*signal handler Ctrl+C*/
  14 #include <stdio.h>      /*printf*/
  15 #include <sched.h>      /*sheduler*/
  16 #include <unistd.h>     /*usleep*/
  17 #include <pthread.h>    /*threads*/
  18 #include <time.h>       /*nanosleep*/
  19
  20 #include "rpin.h"       /*gpclk*/
  21 #include "rp_spi.h"     /*spi*/
  22 #include "misc.h"       /*structure for priorities*/
  23 #include "pxmc_sin_fixed.h"     /*to test sin commutation */
  24
  25
  26
  27 #define PRUM_PROUD      2061
  28 #define PRUM_SOUC       6183
  29 #define MAX_DUTY        128
  30 #define PID_P           0.1
  31
  32 #define PRIOR_KERN      50
  33 #define PRIOR_HIGH      49
  34 #define PRIOR_LOW       20
  35
  36 #define THREAD_SHARED   0
  37 #define INIT_VALUE      1       /*init value for semaphor*/
  38
  39
  40 #define PXMC_SIN_FIX_TAB_BITS 9
  41 #define PXMC_SIN_FIX_IDX_SLR  23
  42 #define PXMC_SIN_FIX_XD_MASK  0x007fffff
  43 #define PXMC_SIN_FIX_XD_SLR   8
  44 #define PXMC_SIN_FIX_A_MASK   0xffffc000
  45 #define PXMC_SIN_FIX_B_SLL    19
  46 #define PXMC_SIN_FIX_B_SAR    16
  47 #define PXMC_SIN_FIX_B_XD_SAR 6
  48 #define PXMC_SIN_FIX_ZIC_MASK 0x00002000
  49 #define PXMC_SIN_FIX_ZIC_BIT  13
  50
  51 #define PXMC_SIN_FIX_PI2      0x40000000
  52 #define PXMC_SIN_FIX_2PI3     0x55555555
  53
  54 #define NSEC_PER_SEC    (1000000000) /* The number of nsecs per sec. */
  55
  56
  57
  58 struct rpi_in data;
  59 struct rpi_state{
  60         uint8_t test;
  61         uint16_t pwm1, pwm2, pwm3;
  62         uint16_t t_pwm1, t_pwm2, t_pwm3;
  63         char commutate;
  64         int duty;                       /* duty cycle of pwm */
  65         uint16_t index_dist;            /* distance to index position */
  66         unsigned char index_ok;
  67         uint32_t tf_count;              /*number of transfer*/
  68         int desired_pos;                /* desired position */
  69 }rps;
  70
  71
  72 /**
  73  * \brief Initilizes GPCLK.
  74  */
  75 int clk_init()
  76 {
  77         initialise(); /*namapovani gpio*/
  78         initClock(PLLD_500_MHZ, 10, 0);
  79         gpioSetMode(4, FSEL_ALT0);
  80         return 0;
  81 }
  82 /*
  83  * \brief Terminates GPCLK.
  84  */
  85
  86 inline void clk_disable(){
  87         termClock(0);
  88 }
  89
  90 /**
  91  * \brief Signal handler pro Ctrl+C
  92  */
  93 void appl_stop(){
  94         spi_disable();
  95         clk_disable();
  96         /*muzeme zavrit semafor*/
  97         sem_destroy(&thd_par_sem);
  98         printf("\nprogram bezpecne ukoncen\n");
  99 }
 100
 101 void substractOffset(struct rpi_in* data, struct rpi_in* offset){
 102         data->pozice_raw=data->pozice;
 103         data->pozice-=offset->pozice;
 104         return;
 105 }
 106 /*
 107  * pocita procentualni odchylku od prumerneho proudu
 108  */
 109 float diff_p(float value){
 110         return ((float)value-PRUM_PROUD)*100/PRUM_PROUD;
 111 }
 112 /*
 113  * pocita procentualni odchylku od prumerneho souctu proudu
 114  */
 115 float diff_s(float value){
 116         return ((float)value-PRUM_SOUC)*100/PRUM_SOUC;
 117 }
 118 /*
 119  * tiskne potrebna data
 120  */
 121 void printData(){
 122         struct rpi_in data_p;
 123         struct rpi_state s;     /*state*/
 124         float cur0, cur1, cur2;
 125         int i;
 126         /* copy the data */
 127         sem_wait(&thd_par_sem);
 128         data_p = data;
 129         s=rps;
 130         sem_post(&thd_par_sem);
 131
 132         if (data_p.adc_m_count){
 133                 cur0=data_p.ch0/data_p.adc_m_count;
 134                 cur1=data_p.ch1/data_p.adc_m_count;
 135                 cur2=data_p.ch2/data_p.adc_m_count;
 136         }
 137         for (i = 0; i < 16; i++) {
 138                         if (!(i % 6))
 139                                 puts("");
 140                         printf("%.2X ", data_p.debug_rx[i]);
 141         }
 142         puts("");
 143         printf("\npozice=%d\n",(int32_t)data_p.pozice);
 144         printf("chtena pozice=%d\n",s.desired_pos);
 145         printf("transfer count=%u\n",s.tf_count);
 146         printf("raw_pozice=%u\n",data_p.pozice_raw);
 147         printf("raw_pozice last12=%u\n",(data_p.pozice_raw&0x0FFF));
 148         printf("index position=%u\n",data_p.index_position);
 149         printf("hal1=%d, hal2=%d, hal3=%d\n",data_p.hal1,data_p.hal2,data_p.hal3);
 150         printf("en1=%d, en2=%d, en3=%d (Last sent)\n",!!(0x40&s.test),!!(0x20&s.test),!!(0x10&s.test));
 151         printf("shdn1=%d, shdn2=%d, shdn3=%d (L.s.)\n",!!(0x08&s.test),!!(0x04&s.test),!!(0x02&s.test));
 152         printf("PWM1=%u(L.s.)\n",s.pwm1);
 153         printf("PWM2=%u(L.s.)\n",s.pwm2);
 154         printf("PWM3=%u(L.s.)\n",s.pwm3);
 155         printf("distance to index=%u\n",s.index_dist);
 156         printf("T_PWM1=%u T_PWM2=%u T_PWM3=%u\n",s.t_pwm1,s.t_pwm2, s.t_pwm3);
 157         printf("Pocet namerenych proudu=%u\n",data_p.adc_m_count);
 158         printf("(pwm1) (ch1)=%d (avg=%4.0f) (%2.2f%%)\n",data_p.ch1,cur1,diff_p(cur1));
 159         printf("(pwm2) (ch2)=%d (avg=%4.0f)(%2.2f%%)\n",data_p.ch2,cur2,diff_p(cur2));
 160         printf("(pwm3) (ch0)=%d (avg=%4.0f)(%2.2f%%)\n",data_p.ch0,cur0,diff_p(cur0));
 161         printf("soucet prumeru=%5.0f (%2.2f%%)\n",cur0+cur1+cur2,diff_s(cur0+cur1+cur2));
 162         printf("duty=%d\n",s.duty);
 163         if (s.index_ok) printf("index ok\n");
 164         if (s.commutate) printf("commutation in progress\n");
 165 }
 166 void prepare_tx(uint8_t * tx){
 167
 168         /*Data format:
 169          * tx[4] - bity 95 downto 88 - bits that are sent first
 170          * tx[5] - bity 87 downto 80
 171          * tx[6] - bity 79 downto 72
 172          * tx[7] - bity 71 downto 64
 173          * tx[8] - bity 63 downto 56
 174          * tx[9] - bity 55 downto 48
 175          * tx[10] - bity 47 downto 40
 176          * tx[11] - bity 39 downto 32
 177          * tx[12] - bity 31 downto 24
 178          * tx[13] - bity 23 downto 16
 179          * tx[14] - bity 15 downto 8
 180          * tx[15] - bity 7 downto 0
 181          *
 182          * bit 95 - ADC reset
 183          * bit 94 - enable PWM1
 184          * bit 93 - enable PWM2
 185          * bit 92 - enable PWM3
 186          * bit 91 - shutdown1
 187          * bit 90 - shutdown2
 188          * bit 89 - shutdown3
 189          *      .
 190          *      .
 191          *      Unused
 192          *      .
 193          *      .
 194          * bits 47 .. 32 - match PWM1
 195          * bits 31 .. 16 - match PWM2
 196          * bits 15 .. 0  - match PWM3
 197          */
 198
 199
 200         uint16_t tmp;
 201
 202         /* keep the 11-bit cap*/
 203
 204         if (rps.pwm1>2047) rps.pwm1=2047;
 205         if (rps.pwm2>2047) rps.pwm2=2047;
 206         if (rps.pwm3>2047) rps.pwm3=2047;
 207
 208         tx[0]=rps.test; /*bit 94 - enable PWM1*/
 209
 210         /*now we have to switch the bytes due to endianess */
 211         /* ARMv6 & ARMv7 instructions are little endian */
 212         /*pwm1*/
 213         tx[10]=((uint8_t*)&rps.pwm1)[1]; /*MSB*/
 214         tx[11]=((uint8_t*)&rps.pwm1)[0]; /*LSB*/
 215
 216         /*pwm2*/
 217         tx[12]=((uint8_t*)&rps.pwm2)[1]; /*MSB*/
 218         tx[13]=((uint8_t*)&rps.pwm2)[0]; /*LSB*/
 219
 220         /*pwm3*/
 221         tx[14]=((uint8_t*)&rps.pwm3)[1]; /*MSB*/
 222         tx[15]=((uint8_t*)&rps.pwm3)[0]; /*LSB*/
 223
 224
 225 }
 226 /**
 227  * Funkce pravidelne vypisuje posledni zjistenou pozici lokalniho motoru
 228  */
 229 void * pos_monitor(void* param){
 230         while(1){
 231                 printData();
 232                 usleep(1000000);        /*1 Hz*/
 233         }
 234         return (void*)0;
 235 }
 236 /*
 237  * \brief
 238  * Multiplication of 11 bit
 239  */
 240 inline int16_t mult_cap(int32_t s,int d){
 241         int j;
 242         int res=0;
 243         for(j=0;j!=11;j++){
 244                 /* multiplicate as if maximum sinus value was unity */
 245                 res+=(!(s & 0x10000000))*(((1 << j) & s)>>j)*(d>>(10-j));
 246         }
 247         return res;
 248 }
 249 inline
 250 int sin_commutator(int duty){
 251         #define DEGREE_60        715827883
 252         #define DEGREE_120      1431655765
 253         #define DEGREE_180      2147483648
 254         #define DEGREE_240      2863311531
 255         #define DEGREE_300      3579139413
 256         uint32_t j,pos;
 257         int32_t sin;
 258         pos=rps.index_dist*4294967;
 259         if (duty>=0){   /*clockwise rotation*/
 260                 /* 1st phase */
 261                 sin = pxmc_sin_fixed_inline(pos+DEGREE_240,10); /*10+1 bity*/ /*-120*/
 262                 rps.pwm1=mult_cap(sin, duty);
 263
 264                 /* 2nd phase */
 265                 sin = pxmc_sin_fixed_inline(pos+DEGREE_120,10); /*10+1 bity*/ /*-240*/
 266                 rps.pwm2=mult_cap(sin, duty);;
 267
 268                 /* 3rd phase */
 269                 sin = pxmc_sin_fixed_inline(pos,10); /*10+1 bity*/
 270                 rps.pwm3=mult_cap(sin, duty);;
 271         }else{
 272                 duty=-duty;
 273
 274                 /* 1st phase */
 275                 sin = pxmc_sin_fixed_inline(pos+DEGREE_60,10); /*10+1 bity*/ /*-300*/
 276                 rps.pwm1=mult_cap(sin, duty);
 277
 278                 /* 2nd phase */
 279                 sin = pxmc_sin_fixed_inline(pos+DEGREE_300,10); /*10+1 bity*/ /*-60-*/
 280                 rps.pwm2=mult_cap(sin, duty);
 281
 282                 /* 3rd phase */
 283                 sin = pxmc_sin_fixed_inline(pos+DEGREE_180,10); /*10+1 bity*/ /*-180*/
 284                 rps.pwm3=mult_cap(sin, duty);
 285         }
 286         return 0;
 287 }
 288 /*
 289  * \brief
 290  * Test function to be placed in controll loop.
 291  * Switches PWM's at point where they produce same force.
 292  * This points are found thanks to IRC position,
 293  */
 294 inline
 295 void simple_ind_dist_commutator(int duty){
 296         if (duty>=0){ /* clockwise - so that position increase */
 297                 /* pwm3 */
 298                 if ((rps.index_dist>=45 && rps.index_dist<=373) ||
 299                 (rps.index_dist>=1048 && rps.index_dist<=1377)){
 300                         rps.pwm1=0;
 301                         rps.pwm2=0;
 302                         rps.pwm3=duty;
 303                         /* pwm1 */
 304                 }else if ((rps.index_dist>=373 && rps.index_dist<=711) ||
 305                 (rps.index_dist>=1377 && rps.index_dist<=1711)){
 306                         rps.pwm1=duty;
 307                         rps.pwm2=0;
 308                         rps.pwm3=0;
 309                         /* pwm2 */
 310                 }else if ((rps.index_dist>=0 && rps.index_dist<=45) ||
 311                 (rps.index_dist>=711 && rps.index_dist<=1048) ||
 312                 (rps.index_dist>=1711 && rps.index_dist<=1999)){
 313                         rps.pwm1=0;
 314                         rps.pwm2=duty;
 315                         rps.pwm3=0;
 316                 }
 317         }else{  /*counter-clockwise - position decrease */
 318                 /* pwm3 */
 319                 if ((rps.index_dist>=544 && rps.index_dist<=881) ||
 320                 (rps.index_dist>=1544 && rps.index_dist<=1878)){
 321                         rps.pwm1=0;
 322                         rps.pwm2=0;
 323                         rps.pwm3=-duty;
 324                         /* pwm1 */
 325                 }else if ((rps.index_dist>=0 && rps.index_dist<=211) ||
 326                 (rps.index_dist>=881 && rps.index_dist<=1210) ||
 327                 (rps.index_dist>=1878 && rps.index_dist<=1999)){
 328                         rps.pwm1=-duty;
 329                         rps.pwm2=0;
 330                         rps.pwm3=0;
 331                         /* pwm2 */
 332                 }else if ((rps.index_dist>=211 && rps.index_dist<=544) ||
 333                 (rps.index_dist>=1210 && rps.index_dist<=1544)){
 334                         rps.pwm1=0;
 335                         rps.pwm2=-duty;
 336                         rps.pwm3=0;
 337                 }
 338         }
 339 }
 340 /*
 341  * \brief
 342  * Test function to be placed in controll loop.
 343  * Switches PWM's at point where they produce same force
 344  */
 345 inline void simple_hall_commutator(int duty){
 346         if (duty>=0){ /* clockwise - so that position increase */
 347                 /* pwm3 */
 348                 if (data.hal2 && !data.hal3){
 349                         rps.pwm1=0;
 350                         rps.pwm2=0;
 351                         rps.pwm3=duty;
 352                         /* pwm1 */
 353                 }else if (data.hal1 && !data.hal2){
 354                         rps.pwm1=duty;
 355                         rps.pwm2=0;
 356                         rps.pwm3=0;
 357                         /* pwm2 */
 358                 }else if (!data.hal1 && data.hal3){
 359                         rps.pwm1=0;
 360                         rps.pwm2=duty;
 361                         rps.pwm3=0;
 362                 }
 363         }else{  /*counter-clockwise - position decrease */
 364                 /* pwm3 */
 365                 if (!data.hal2 && data.hal3){
 366                         rps.pwm1=0;
 367                         rps.pwm2=0;
 368                         rps.pwm3=-duty;
 369                         /* pwm1 */
 370                 }else if (!data.hal1 && data.hal2){
 371                         rps.pwm1=-duty;
 372                         rps.pwm2=0;
 373                         rps.pwm3=0;
 374                         /* pwm2 */
 375                 }else if (data.hal1 && !data.hal3){
 376                         rps.pwm1=0;
 377                         rps.pwm2=-duty;
 378                         rps.pwm3=0;
 379                 }
 380         }
 381 }
 382 /**
 383  * \brief
 384  * Computation of distance to index.
 385  *
 386  * K dispozici je 12-bit index, to umoznuje ulozit 4096 ruznych bodu
 387  * Je nutne vyjadrit 1999 bodu proti i posmeru h.r. od indexu -
 388  *      to je 3999 bodu
 389  *      =>12 bitu je dostacujicich, pokud nikdy nedojde ke ztrate
 390  *              signalu indexu
 391  */
 392 void comIndDist(){
 393         uint16_t pos = 0x0FFF & data.pozice_raw;
 394         uint16_t dist;
 395         uint16_t index = data.index_position;
 396
 397         if (index<1999){                /*index e<0,1998> */
 398                 if (pos<index){                 /*pozice e<0,index-1> */
 399                         /*proti smeru h.r. od indexu*/
 400                         dist=pos+2000-index;
 401                 }else if (pos<=index+1999){     /*pozice e<index,index+1999> */
 402                         /*po smeru h.r. od indexu*/
 403                         dist=pos-index;
 404                 }else if (pos<index+2096){      /*pozice e<index+2000,index+2095> */
 405                         goto index_lost;
 406                 }else{                          /*pozice e<index+2096,4095> */
 407                         /*proti smeru h.r. od indexu - podtecena pozice*/
 408                         dist=pos-index-2096;
 409                 }
 410         }else if (index<=2096){         /*index e<1999,2096>*/
 411                 if (pos<index-1999){            /*pozice e<0,index-2000> */
 412                         goto index_lost;
 413                 }else if (pos<index){           /*pozice e<index-1999,index-1> */
 414                         /*proti smeru h.r. od indexu*/
 415                         dist=pos+2000-index;
 416                 }else if (pos<=index+1999){     /*pozice e<index,index+1999> */
 417                         /*po smeru h.r. od indexu*/
 418                         dist=pos-index;
 419                 }else {                         /*pozice e<index+2000,4095> */
 420                         goto index_lost;
 421                 }
 422         }else{                          /*index e<2097,4095> */
 423                 if (pos<=index-2097){           /*pozice e<0,index-2097> */
 424                         /*po smeru h.r. od indexu - pretecena pozice*/
 425                         dist=4096+pos-index;
 426                 }else if (pos<index-1999){      /*pozice e<index-2096,index-2000> */
 427                         goto index_lost;
 428                 }else if (pos<index){           /*pozice e<index-1999,index-1> */
 429                         /*proti smeru h.r. od indexu*/
 430                         dist=pos+2000-index;
 431                 }else{                          /*pozice e<index,4095> */
 432                         /*po smeru h.r. od indexu*/
 433                         dist=pos-index;
 434                 }
 435         }
 436
 437         rps.index_dist = dist;
 438         return;
 439
 440         index_lost:
 441                 rps.index_ok=0;
 442                 return;
 443 }
 444 /*
 445  * \brief
 446  * Very simple PID regulator.
 447  * Now only with P-part so that the error doesnt go to zero.
 448  * TODO: add anti-wind up and I and D parts
 449  */
 450 inline void pid(){
 451         int duty_tmp;
 452         duty_tmp = PID_P*(rps.desired_pos - (int32_t)data.pozice);
 453         if (duty_tmp>MAX_DUTY){
 454                 rps.duty=MAX_DUTY;
 455         }else if (duty_tmp<-MAX_DUTY){
 456                 rps.duty=-MAX_DUTY;
 457         }else{
 458                 rps.duty = duty_tmp;
 459         }
 460 }
 461 /*
 462  * \brief
 463  * Feedback loop.
 464  */
 465 void * read_data(void* param){
 466         int i;
 467         struct rpi_in pocatek;
 468         struct timespec t;
 469         int interval = 1000000; /* 1ms ~ 1kHz*/
 470         uint8_t tx[]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} ;
 471         char first=1;
 472         uint16_t last_index;                            /*we have index up-to date*/
 473         pocatek = spi_read(tx);
 474         clock_gettime(CLOCK_MONOTONIC ,&t);
 475         /* start after one second */
 476         t.tv_sec++;
 477                 while(1){
 478                         /* wait until next shot */
 479                         clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &t, NULL);
 480                         sem_wait(&thd_par_sem);         /*---take semaphore---*/
 481                         prepare_tx(tx);                 /*save the data to send*/
 482                         data = spi_read(tx);            /*exchange data*/
 483                         /*subtract initiate postion */
 484                         rps.tf_count++;
 485                         substractOffset(&data,&pocatek);
 486                         comIndDist();
 487                         if (!rps.index_ok){
 488                                 if (first){
 489                                         last_index=data.index_position;
 490                                         first=0;
 491                                 }else if (last_index!=data.index_position){
 492                                         rps.index_ok=1;
 493                                 }
 494                         }
 495                         pid();
 496                         if (rps.index_ok && rps.commutate){
 497                                 /*simple_ind_dist_commutator(rps.duty);*/
 498                                 sin_commutator(rps.duty);
 499                         }else if(!rps.index_ok && rps.commutate){
 500                                 simple_hall_commutator(rps.duty);
 501                         }
 502                         sem_post(&thd_par_sem);         /*--post semaphore---*/
 503
 504                         /* calculate next shot */
 505                         t.tv_nsec += interval;
 506
 507                         while (t.tv_nsec >= NSEC_PER_SEC) {
 508                                 t.tv_nsec -= NSEC_PER_SEC;
 509                                 t.tv_sec++;
 510                         }
 511
 512                 }
 513 }
 514
 515
 516 /**
 517  * \brief
 518  * Commands detection.
 519  */
 520 void poll_cmd(){
 521         unsigned int tmp;
 522         /*
 523          * Note:
 524          * pri pouziti scanf("%u",&simple_hall_duty); dochazelo
 525          * k preukladani hodnot na promenne test. Dost divne.
 526          */
 527         while (1){
 528                 scanf("%u",&tmp);
 529                 printf("volba=%u\n",tmp);
 530                 switch (tmp){
 531                 case 1:
 532                         scanf("%u",&tmp);
 533                         sem_wait(&thd_par_sem);
 534                         rps.pwm1=tmp&0xFFF;
 535                         sem_post(&thd_par_sem);
 536                         break;
 537                 case 2:
 538                         scanf("%u",&tmp);
 539                         sem_wait(&thd_par_sem);
 540                         rps.pwm2=tmp&0xFFF;
 541                         sem_post(&thd_par_sem);
 542                         break;
 543                 case 3:
 544                         scanf("%u",&tmp);
 545                         sem_wait(&thd_par_sem);
 546                         rps.pwm3=tmp&0xFFF;
 547                         sem_post(&thd_par_sem);
 548                         break;
 549                 case 4:
 550                         scanf("%u",&tmp);
 551                         sem_wait(&thd_par_sem);
 552                         rps.test=tmp&0xFF;
 553                         sem_post(&thd_par_sem);
 554                         break;
 555                 case 5:
 556                         sem_wait(&thd_par_sem);
 557                         rps.commutate=!rps.commutate;
 558                         /* switch off pwms at the end of commutation */
 559                         rps.pwm1&=rps.commutate*0xFFFF;
 560                         rps.pwm2&=rps.commutate*0xFFFF;
 561                         rps.pwm3&=rps.commutate*0xFFFF;
 562                         sem_post(&thd_par_sem);
 563                         break;
 564                 case 6:
 565                         scanf("%d",&tmp);
 566                         sem_wait(&thd_par_sem);
 567                         rps.duty=tmp;
 568                         sem_post(&thd_par_sem);
 569                         break;
 570                 case 7:
 571                         scanf("%d",&tmp);
 572                         sem_wait(&thd_par_sem);
 573                         rps.desired_pos=tmp;
 574                         sem_post(&thd_par_sem);
 575                         break;
 576
 577                 default:
 578                         break;
 579                 }
 580
 581         }
 582         return ;
 583 }
 584 /**
 585  * \brief Main function.
 586  */
 587
 588 int main(){
 589         pthread_t base_thread_id;
 590         clk_init();             /* inicializace gpio hodin */
 591         spi_init();             /* iniicializace spi*/
 592
 593         /*semafor pro detekci zpracovani parametru vlaken*/
 594         sem_init(&thd_par_sem,THREAD_SHARED,INIT_VALUE);
 595         setup_environment();
 596
 597         base_thread_id=pthread_self();
 598
 599         /*main control loop*/
 600         create_rt_task(&base_thread_id,PRIOR_HIGH,read_data,NULL);
 601
 602         /*monitor of current state*/
 603         create_rt_task(&base_thread_id,PRIOR_LOW,pos_monitor,NULL);
 604
 605         /*wait for commands*/
 606         poll_cmd();
 607
 608         return 0;
 609 }