this is my first electronics project which requires controlling 2 different stepper motors with two motor drivers (L293D). I have found that the number of GPIO pins on my microcontroller (ESP8266) is 9. However, i require 10. I have found on the arduino website a method of using a transistors as switches as shown below which would reduce the amount of pins needed on the microcontroller.
My question is what do the wires control 1 and 2 lead to? is it just back to the GPIO pins of the microcontroller and i code for when the transistors turn on and off, or is there another piece of equipment in between? Also, where do I start from when choose what resistors and transistors to use? Thanks