ESP8266 Community Forum

BE sure to change the CS pin because the ESP8266 standard CS pin is IO15 which always has to be connected to ground!(in this case change it to 2)

I was wondering about this . Did you make a mistake?GPIO15 pin is not a chip select pin as far as I know . It is the MTDO pin used to boot the chip into a SDIO mode which no-one seems to know much about yet . Its a slave mode for SPI I think though

I think you can use any pin that will go high to act as CS (Chip Select) pin

Hi,
when you look on the pin table from the Repository:

(From:https://raw.githubusercontent.com/Links2004/Arduino/esp8266/docs/pin_functions.png)

You can see that Function 2 of IO15 is HSPICS.

To boot the esp normaly, you need to connect IO15 to Ground. Nearly every espboard has it's io 15 connected to ground. Excluding my esp8266 201, where I had to solder wires on.

Here is a quick schematic I've wrote:

You could do with some 10K resistores on some lines and GPIO15 if broken out should be pulled low via a 10K resistor to ensure the chip does not go into SDIO mode.
See the wiki above for circuits and info