From the article machine.Pin, it has been discussed using a microcontroller pin to import and export data and in the article I2C bus communication which uses the machine.I2C class to communicate between devices. Now let’s take a look at the machine.SPI class, another form of communication that has been recognized for its speed and is commonly used with a graphics display (esp8266/esp32 article) or SD-Card reader (esp8266, esp32article).