AT+CFUN=0/AT+CFUN=4 is not confirned with "OK".(NCS1.3.0)

Question

I add lte_lc_init_and_connect() to the application "Serial LTE Modem" (SLM) v1.3.0. And then there's no reaction to AT+CFUN=0 or AT+CFUN=4. 
 static int modem_configure(void){
#if defined(CONFIG_BSD_LIBRARY)
	if (IS_ENABLED(CONFIG_LTE_AUTO_INIT_AND_CONNECT)) {
 /* Do nothing, modem is already turned on */
 /* and connected */
 goto connected;
	}

	LOG_INF("Connecting to LTE network.");
	LOG_INF("This may take several minutes.");

#if defined(CONFIG_LWM2M_CARRIER)
	/* Wait for the LWM2M carrier library to configure the */
	/* modem and set up the LTE connection. */
	k_sem_take(&lte_connected, K_FOREVER);
#else /* defined(CONFIG_LWM2M_CARRIER) */
	int err = lte_lc_init_and_connect();
	if (err) {
 LOG_ERR("LTE link could not be established.");
 return err;
	}
#endif /* defined(CONFIG_LWM2M_CARRIER) */

connected:
	LOG_INF("Connected to LTE network.");

#endif /* defined(CONFIG_BSD_LIBRARY) */
	return 0;
}

void start_execute(void)
{
	int err;

	LOG_INF("Serial LTE Modem");

+	while (modem_configure() != 0) {
+ LOG_WRN("Failed to establish LTE connection.");
+ LOG_WRN("Will retry in %d seconds.", 10);
+ k_sleep(K_SECONDS(10));
+	}

	err = modem_info_init();
	if (err) {
 LOG_ERR("Modem info could not be established: %d", err);
 return;
	}

	modem_info_params_init(&modem_param);

	/* Initialize AT Parser */
	err = at_params_list_init(&at_param_list, CONFIG_SLM_AT_MAX_PARAM);
	if (err) {
 LOG_ERR("Failed to init AT Parser: %d", err);
 return;
	}

	err = slm_at_host_init();
	if (err) {
 LOG_ERR("Failed to init at_host: %d", err);
 return;
	}

	k_work_q_start(&slm_work_q, slm_wq_stack_area,
 K_THREAD_STACK_SIZEOF(slm_wq_stack_area), SLM_WQ_PRIORITY);
	k_work_init(&exit_idle_work, exit_idle);
} 
 I find that the socket_thread_fn() in at_cmd.c does not respond "OK
". 
 It returns "+CSCON: 1
" and "+CEREG: 0,"1D2C","0D61D950",9,0,0,"11100000","11100000"
"

So no messages are put on the queue. The program is blocked at_write(). 
 static inline int at_write(const char *const cmd, enum at_cmd_state *state)
{
	int bytes_sent;
	int bytes_to_send = strlen(cmd);
	struct return_state_object ret;

	LOG_DBG("Sending command %s", log_strdup(cmd));

	bytes_sent = send(common_socket_fd, cmd, bytes_to_send, 0);

	if (bytes_sent == -1) {
 LOG_ERR("Failed to send AT command (err:%d)", errno);
 ret.code = -errno;
 ret.state = AT_CMD_ERROR;
	} else {
 LOG_DBG("Awaiting response for %s", log_strdup(cmd));
 k_msgq_get(&return_code_msq, &ret, K_FOREVER); //It's blocked here
 LOG_DBG("Bytes sent: %d", bytes_sent);

 if (bytes_sent != bytes_to_send) {
 LOG_ERR("Bytes sent (%d) was not the "
 "same as expected (%d)",
 bytes_sent, bytes_to_send);
 }
	}

	if (state) {
 *state = ret.state;
	}

	return ret.code;
}

Martin Lesund · Answer

Hi,
Thank you for the additional observations and feedback.
I can replicate what you are seeing as well so we are working on this internally to see what we can to solve this.
Hopefully this workaround is sufficient for you as of now.

If not then I would recommend setting up the modem "manually" with the AT commands to avoid the issue entirely.