(ESP8266) Why os_printf() of example"at_espconn" did not return any log in uart?

[cks2074243]

I used example of at_espconn to test at espconnect. AT command was transfered from TCP server to ESP8266 successfuly and i can get return information from ESP8266 TO TCP server. like

【2017-06-06 10:12:29:236】
+IPD,8:AT+GMR
【2017-06-06 10:12:29:443】AT+GMR
AT version:1.3.0.0(Jul 14 2016 18:54:01)
SDK version:2.0.0(656edbf)
compile time:Jun 6 2017 10:03:17
OK

But the os_printf() in the espconn callback funtion did not return any log in the uart. Like the connect_cb below, the uart did not return "at demo espconn connected\r\n" in the uart.

at_espconn_demo_connect_cb(void *arg)
{
os_printf("at demo espconn connected\r\n");
espconn_set_opt((struct espconn*)arg,ESPCONN_COPY);
at_espconn_demo_flag = TRUE;
at_espconn_demo_data_len = 0;
}

Why this happen? i used SDKv2.1.0 and SDK v2.0.0 to try this example, but the logs are all missing .
could someone help me?

[Her Mary]

If using AT, UART0 is for AT commands, UART1 for debug log.