The ESP8266 was introduced about two years ago. At first the only software for it was based on its AT Command Set. Many of the example programs found on the internet are based on it.
Over the months Espressif Systems have released upgrades to the AT Command Set. In a few cases certain commands have been removed. In other cases the response has changed. The net result is that a sketch that was found on the internet, while it may have worked perfectly for the author, may generate errors if a different version of the AT Command Set is programmed into your ESP8266. This leads to much debugging frustration.
The documentation for the latest versions can be found on the Espressif website but docs for older versions are harder to find. To ease the search I have posted several below.
I recently received a NodeMCU from banggood.com that didn't seem to have a normal AT Command Set at all. On power up I got (9600 baud):
NodeMcu 0.9.6 (Doit.am Version) build 20150701 powered by Lua 5.1.4
ESP8266 Started Start soft AP >
When I tried the AT+RST command I got:
> AT+RST stdin:1: '=' expected near '+' >
I have no idea what that means and I don't know it is programmed into any ESP8266 ESP-01 modules.
This page written by Roger Schaefer. Last updated March 23,