The4 pin .96" SSD1306 displays typically use what's called the I2C (Inter-IC Communication) bus and 7 pin versions use what's called SPI (Serial Peripheral Interface). SPI is the faster of the two, but obviously requires more connections. I have both, but unless I need fast redraw speeds, I usually just use I2C for convenience. Toturn the LED off, set pin mode to INPUT. To turn the LED on, first digitalWrite LOW to the pin, then set pin mode to OUTPUT. To poll the switch, first set pin mode to INPUT, then digitalWrite HIGH to the pin. After reading the switch, do (1) or (2) to restore the desired LED state. .Product.Guide.103.1.—.C:3 and 7-pin interchangeable Cores Applications,.Features,.and.How.to.Order.-.Nomenclature 6-pin and 7-pin LEDPin: The board has an inbuilt LED using digital pin-13. The LED glows only when the digital pin becomes high. AREF Pin: This is an analog reference pin of the Arduino board. It is used to provide a reference voltage from an external power supply. Arduino Nano. The Arduino Uno and nano are similar, but the only difference is that its Afterlooking at the Hardware Manual I'm also thinking that the I/O mux registers are complicated enough that the Arduino Core for ESP32 missed some small detail that prevents fast switching of pins 32/33 between IN and OUT. Or some other issue. The point is, OneWire works on pins 13 and 25, but doesn't on pins 32 and 33. §4.1.1 The differences are that all positive signals of the differential pairs are swapped with their corresponding shield, the DDC/CEC Ground is assigned to pin 13 instead of pin 17, the CEC is assigned to pin 14 instead of pin 13, and the reserved pin is 17 instead of pin 14. Asnouns the difference between shaft and pin is that shaft is the entire body of a long weapon, such as an arrow while pin is a small device, made (usually) of drawn-out steel wire with one end sharpened and the other flattened or rounded into a head, used for fastening. As verbs the difference between shaft and pin is that shaft is to fuck over; to Differencewith 7-pin connector. Of course, there are differences between the two plugs. A 7-pole plug is intended to provide the trailer with basic lighting. A 13-pole plug ensures Whydo people use a variable to specify a pin number when the pin is unlikely to change throughout the execution of the code? Many times I see an int being used for a pin definition, int led = 13; when the use of a const int. const int led = 13; or enum, or #define. #define LED 13 makes much more sense. Ifanyone has a definitive answer on what the function of the rubber bushing is, please post it in the comments below! And if you've been forum hopping like huCn0Q.