ESP8266 Pinout Reference: Which GPIO pins should you use?

Jovan Stosic August 26, 2020
Label GPIO Input Output Notes
D0 GPIO16 no interrupt no PWM or I2C support HIGH at boot
used to wake up from deep sleep
D1 GPIO5 OK OK often used as SCL (I2C)
D2 GPIO4 OK OK often used as SDA (I2C)
D3 GPIO0 pulled up OK connected to FLASH button, boot fails if pulled LOW
D4 GPIO2 pulled up OK HIGH at boot
connected to on-board LED, boot fails if pulled LOW
D5 GPIO14 OK OK SPI (SCLK)
D6 GPIO12 OK OK SPI (MISO)
D7 GPIO13 OK OK SPI (MOSI)
D8 GPIO15 pulled to GND OK SPI (CS)
Boot fails if pulled HIGH
RX GPIO3 OK RX pin HIGH at boot
TX GPIO1 TX pin OK HIGH at boot
debug output at boot, boot fails if pulled LOW
A0 ADC0 Analog Input X

Source: ESP8266 Pinout Reference: Which GPIO pins should you use? | Random Nerd Tutorials

Crimean War

Jovan Stosic August 25, 2020

The Crimean War was a military conflict fought from October 1853 to February 1856 in which Russia lost to an alliance made up of the Ottoman Empire, the United Kingdom, Sardinia and France. The immediate cause of the war involved the rights of Christian minorities in the Holy Land, which was a part of the Ottoman Empire. The French promoted the rights of Roman Catholics, while Russia promoted those of the Eastern Orthodox Church. The longer-term causes involved the decline of the Ottoman Empire and the unwillingness of Britain and France to allow Russia to gain territory and power at the Ottoman Empire’s expense. It has widely been noted that the causes, in one case involving an argument over the keys to the Church of the Nativity, revealed a “great confusion of purpose”, yet they led to a war noted for its “notoriously incompetent international butchery”.

https://en.m.wikipedia.org/wiki/Crimean_War