ESP8266 Community Forum

Working with ESP-01 and a serial module works great and i can use the serial monitor to output debugging information. My program works fine however after disconnecting the serial adapter from the ESP-01 problems begin. The module connects to wifi correctly but programs which use the gpio 0 / 2 pins cease to do their job. I had this problem with a simple GPIO in and out program, and now the same with a 1-Wire sensor. This effect is even when no output is sent to the serial interface.

I am using NodeMCU 2.10. Is there a pullup or pulldown required on the serial inputs when they are not used?

Thanks for any ideas, Thomas

I found that a pull up resistor on the RX line got rid of problems that I saw when I didn't have a serial connection. I always include it now.

Yes, you are right Rudi, I recommend it too and during normal operation, I strongly recommend to disconnect the USB / RS232 converter. Connected converter with power supply off, may cause instability of module ESP8266.
http://esp8266.fancon.cz/esp8266-web-hygrometer-dht11-arduino/esp8266-web-hygrometer-dht11-arduino.html

Problem solved!

Unfortunately the pullup's did'nt help. But as I tried to connect an oscilloscope to find what's the problem, the ESP began to work correctly. It was the earth connection . I used an insulated power supply and did not connect the earth wire to the negative output. The USB converter gave the earth connection via computer. Afterwards the ESP works properly.

Hope this helps others too,