- Sat Sep 08, 2018 5:54 pm
#78147
petrkr wrote:I just do not know why GPIO15 (D8) can not be used for this module. For SPI display it works fine.
Petrkr,
Just as Shufti says, the W5500 has a pull-up resistor which, if the CS is connected directly to GPIO15, will force the ESP8266 into SDIO mode, which means that it won't do a normal boot from flash.
You -can- use GPIO15, even with boards like the W5500 which have a pull-up resistor; you just need to buffer the output of the pin so that the pull-up isn't "seen" by the ESP8266 (effectively, you are ensuring that the pin can only ever be an output and never an input).
Please look at the link (already posted above) for the (very simple) one transistor circuit to make this work:-
https://esp8266hints.wordpress.com/2018/02/13/adding-an-ethernet-port-to-your-esp-revisited/