Hi Joseph, I have encountered a problem of transmission data via UART port. At first, I used Serial 2(PA_2:TX, PA_3:Rx) as ESP8266 connection port, and it looked like normally operating beside the debug message not present at all (both in Web IDE and yotta). Therefore, I changed several different UART ports and ran the codes in both yotta and Web IDE. It was odd that running the codes was perfectly fine in Web IDE while it was crush all the time in yotta. I couldn't figure out what's wrong there. I have checked the codes for UART setting and configurations. Still couldn't find out. If you have time to check on it, I really appreciate. By the way, I'm attaching source code of my module which may help you to understand the dilemma I am facing now. Thanks, Hank[[/media/uploads/hank51017/nucleo_i2c_oled_bme280_copy.zip]]