Hi, thank for all responses. When program start, esp8266's led is blinking, so I think it's not about the current which TM4C supplies, when I try Serial2.begin(9600), it doesn't show anything , when I try both Serial with 115200 baud rates, it show just like example above I have try "AT" and "AT+GMR" but nothing happen at all, it reads and shows exactly character that I send to it.