ESP8266 Community Forum

I know the difference between these two is the amount of flash, the lack of a power LED, and the other LED being on the Txd signal on the "01" and on the GPIO2 on the "01S"... The problem I have is that I have code that works on the ESP-01, but the same code does not work the ESP-01S. I am using the same board; simply swapping the esp-01 boards in and out of the socket I have for it. The code does not use the GPIO pins, all it does is connect automatically to the wireless router I have, and hosts a webpage. On the "01" board it will take about 1-2 seconds before it connects wirelessly and shows its IP address. The same code on the "01S" board just sits there (sending dots to terminal screen) as it tries to connect.

Were there any pinout or circuit differences on the ESP-01S vs. the ESP-01 (aside from the missing 2nd LED on the ESP-01S)?

I don't think it is a power supply issue, and I am now using a proper supply (before I was able to get away with USB power).

I added a 100nF cap between 3.3V and GND pin on the "01S" board, as I did on the "01" board

The "01" board is over 3 years old, the "01S" I ordered/received just last week

I am using Arduino IDE to program the boards. There seems to be no issue programming.

There should be no difference, try compiling with Flash Mode == DIO and then try QIO, I saw this affect things once...

Other than that I am betting on bad power to the board, brown outs, bad grounds, bad board, etc....

RichardS

There were some ESP-01 that we built with an odd flash chip. There was a fix put in the ESP8266-Arduino project to deal with this. If you have an older version of the IDE then this ]might be the issue. (or not) I don't recall all the details since I never use the ESP-01 boards. I saw it in an issue entered into the issue system.

I'm assuming that you probably are using the Arduino framework. Even if no, it might be applicable.

SOLUTION: Router settings!

The older Esp-01 worked find with router security set to open, while the newer ESP-01S required security to be set to WPA2-personal on the wireless router! Perhaps the 'S' stands for security (I have scoured the internet, and there is no explanation what the S stands for in the newer module)... although I am not sure who would want to hack into my wifi to control my LED!