Shell commands does not enter the prompt

Hi everyone: I have written this code taken by an existing one. I gives the "make BOARD=nucleo-f401re flash term " command in order to compile and flash on my Board but, at the end , it does not enter the shell. I mean that I expect (at the end of compiling and execution) the pyterm prompt in order to issue the commands . But nothing . It seems to stop to the execution of the last line of code .: shell_run(shell_commands, line_buf, SHELL_DEFAULT_BUFSIZE); What is the problem ? Thank you for your help.

    #include <sys/types.h>
    #include <sys/stat.h>

    #include <unistd.h>
    #include <fcntl.h>
    #include <time.h>
    #include <stdio.h>
    #include <string.h>
    #include <stdlib.h>
    #include "thread.h"
    #include "shell.h"
    #include "shell_commands.h"
    #include "periph/adc.h"
    #include "periph/gpio.h"
    #include "analog_util.h"
    #include "xtimer.h"
    #include "periph/timer.h"
    #include "msg.h"
    #include "net/emcute.h"
    #include "net/ipv6/addr.h"

    #define ADC_IN_USE                  ADC_LINE(0)
    #define ADC_IN_USE1                 ADC_LINE(1)
    #define GPIO_IN_USE                 GPIO_PIN(0,10)
    #define ADC_RES                     ADC_RES_12BIT
    #define ADC_RES1                    ADC_RES_12BIT

    #define RES             ADC_RES_10BIT
    #define DELAY           (100LU * US_PER_MS) /* 1000 ms */

    #define NUMOFSUBS           (16U)
    #define TOPIC_MAXLEN        (64U)

    #define _IPV6_DEFAULT_PREFIX_LEN        (64U)

    #ifndef EMCUTE_ID
    #define EMCUTE_ID ("gertrud")
    #define EMCUTE_PORT (1883U)

    static char stack[THREAD_STACKSIZE_DEFAULT];
    static msg_t queue[8];

     // struct that contains sensors
    typedef struct sensors{
      int moisture;
      int level;


    static void *emcute_thread(void *arg)
        emcute_run(EMCUTE_PORT, EMCUTE_ID);
        return NULL; /* should never be reached */

    // function that disconnects from the mqttsn gateway
    static int discon(void){
        int res = emcute_discon();
        if (res == EMCUTE_NOGW) {
            puts("error: not connected to any broker");
            return 1;
        else if (res != EMCUTE_OK) {
            puts("error: unable to disconnect");
            return 1;
        puts("Disconnect successful");
        return 0;

    // function that publish messages to the topic
    // it takes as input the topic, the message to send and
    // the value of qos
    static int pub(char* topic, char* data, int qos){
      emcute_topic_t t;
      unsigned flags = EMCUTE_QOS_0;

      switch (qos) {
          case 1:
            flags |= EMCUTE_QOS_1;
          case 2:
            flags |= EMCUTE_QOS_2;
            flags |= EMCUTE_QOS_0;

      /* step 1: get topic id */ = topic;
      if (emcute_reg(&t) != EMCUTE_OK) {
          puts("error: unable to obtain topic ID");
          return 1;

      /* step 2: publish data */
      if (emcute_pub(&t, data, strlen(data), flags) != EMCUTE_OK) {
          printf("error: unable to publish data to topic '%s [%i]'\n",
        , (int);
          return 1;

      printf("published %s on topic %s\n", data, topic);

      return 0;

    // function that connects to the mqtt gateway
    // it takes as input the ip address and the port
    static int con(char* addr, int port){
      sock_udp_ep_t gw = { .family = AF_INET6, .port = EMCUTE_PORT };
      gw.port = port;

      /* parse address */
      if (ipv6_addr_from_str((ipv6_addr_t *)&gw.addr.ipv6, addr) == NULL) {
          printf("error parsing IPv6 address\n");
          return 1;

      if (emcute_con(&gw, true, NULL, NULL, 0, 0) != EMCUTE_OK) {
          printf("error: unable to connect to [%s]:%i\n", addr, port);
          return 1;
      printf("Successfully connected to gateway at [%s]:%i\n", addr, port);
      return 0;
    // function that read sensor values
    static void read_sensors_values(t_sensors* sensors){
       int sample = 0;
       int sample1 = 0;
       sample = adc_sample(ADC_IN_USE, ADC_RES);
       sample1 = adc_sample(ADC_IN_USE1, ADC_RES1);
       sensors->moisture = adc_util_map(sample, ADC_RES, 10, 100);
       sensors->level = adc_util_map(sample1, ADC_RES1, 10, 100);
      /* xtimer_periodic_wakeup(&last, DELAY); */ 
     // new shell command: start the station
    // the function takes in input ip address and port of the gateway,
    // and the id of the specified station
    // every five seconds it generates new sensor values and publish them to 
    // "localgateway_to_awsiot" + station id       
     static int cmd_start(int argc, char **argv){
      if (argc < 4) {
          printf("usage: %s <address> <port> <id>\n", argv[0]);
          return 1;
      // sensors struct
      t_sensors sensors;
      // name of the topic
      char topic[32];
      sprintf(topic,"localgateway_to_awsiot%d", atoi(argv[3]));
      // json that it will published
      char json[128];   
    /* Sample continously the ADC line */
        while (1) {
    xtimer_ticks32_t last = xtimer_now(); 
        // it tries to connect to the gateway
        if (con(argv[1], atoi(argv[2]))) {
    // takes the current date and time
        char datetime[20];
        time_t current;
        struct tm* t = localtime(&current);
        int c = strftime(datetime, sizeof(datetime), "%Y-%m-%d %T", t);
        if(c == 0) {
          printf("Error! Invalid format\n");
          return 0;
      // updates sensor values
       // fills the json document
        sprintf(json, "{\"id\": \"%d\", \"datetime\": \"%s\", \"moisture\": "
                      "\"%d\", \"level\": \"%d\"}",
                      atoi(argv[3]), datetime, sensors.moisture, sensors.level);
          // publish to the topic
        pub(topic, json, 0);    
         xtimer_periodic_wakeup(&last, DELAY);
           // it disconnects from the gateway
          // it sleeps for five seconds

      return 0;

    static const shell_command_t shell_commands[] = {
        {"start", "Start the station", cmd_start},
        {NULL, NULL, NULL}};
     int main(void)
        printf("\r\nMQTT-SN application\r\n");
        printf("\r\nType 'help' to get started. Have a look at the for more information.\r\n");

    /* initialize the ADC line */
        if (adc_init(ADC_IN_USE) < 0) {
            printf ("\r\nInitialization of ADC_LINE(%u) failed\r\n", ADC_IN_USE);
            return 1;
        else {
            printf ("\r\nSuccessfully initialized ADC_LINE(%u)\r\n", ADC_IN_USE);
        if (adc_init(ADC_IN_USE1) < 0) {
            printf("\r\nInitialization of ADC_LINE(%u) failed\r\n", ADC_IN_USE1);
            return 1;
        else {
            printf("\r\nSuccessfully initialized ADC_LINE(%u)\r\n", ADC_IN_USE1);

        /* the main thread needs a msg queue to be able to run `ping6`*/
        msg_init_queue(queue, ARRAY_SIZE(queue));
        /* start the emcute thread */
        thread_create(stack, sizeof(stack), EMCUTE_PRIO, 0,
                emcute_thread, NULL, "emcute");
        /* start shell */
        char line_buf[SHELL_DEFAULT_BUFSIZE];
        shell_run(shell_commands, line_buf, SHELL_DEFAULT_BUFSIZE);
        /* should be never reached */
        return 0;

Formatting is pretty hard to read, maybe it is better to push the code to github and link it?

I edited the original post to have some C highlighting

I had a similar problem a while ago… Have you tried changing priorities in threads? If the one with higher priority doesn’t block a some point, you won’t never have the prompt I guess. Look at the value of EMCUTE_PRIO, compared to the one the shell has