Making CS (chip select) work in SPI (for and SD card and OLED)
I wanted to write to 2 SD cards simultaniously with one Arduino Mega. Used all the relevant pins including CS on 53 for the first SD card and 13 for the second SD card.  Can be any digital pin I think but this one makes the LED blink too).  Before the SD.begin(13) of the second SD card I do a digitalWrite(53,HIGH).  That de-selects the first SD card. and digitalWrite(13,HIGH) when switching back to SD.begin(53) I do a digitalWrite(13,HIGH).  This works real fine.
Now I tried to impelment this on a D1-Mini.  Cannot get it to work.
SD.begin(D8) starts the first SD fine.  By doing a digitalWrite(D8,HIGH) I tried to de-select SD1 and with SD.begin(D4) opened the second card. Strangely enough it still opens the first SD card again regardless of the pinnumber-parameter.
Maybe the SD library for ESP8266 remembers the first setting of the CS and later settings og the parameter with fifferent pinnembers are ignored???