• VCC
• GND
• SCL (Clock)
• SDA (Data)

• VCC: Connect to U1:30 (3V3)
• GND: Connect to U1:15 (GND__1) or U1:16 (GND)
• SCL: Connect to U1:24 (D23)
• SDA: Connect to U1:25 (D22)

• Search for the SSD1306 display in Flux's component library and add it to your schematic.
• Use the designators and connections listed above to wire it to the ESP32.

• Use a library like Adafruit's SSD1306 library for Arduino to control the display.
• Below is a sample initialization code for Arduino IDE:

Cpp
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

#define OLED_RESET    -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

void setup() {
  // Initialize the display
  if(!display.begin(SSD1306_I2C_ADDRESS, OLED_RESET)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }

  // Clear the buffer
  display.clearDisplay();
  display.display();
}

void loop() {
  // Your code to interact with the display
}

• Connect 74HC165 Pin 8 (GND) to U1:GND__1 or U1:GND (ground).
• Connect 74HC165 Pin 16 (VCC) to U1:3V3 (for power).
• Connect 74HC165 Pin 1 (Serial Output, Q7) to a GPIO on ESP32 (let's say U1:D19 for data reading).
• Connect 74HC165 Pin 2 (Clock Inhibit, /INH) to U1:GND to always enable the clock.
• Connect 74HC165 Pin 15 (Clock, CLK) to U1:D18 (for clock signal).
• Connect 74HC165 Pin 11 (Load, /PL) to another GPIO on ESP32 (say U1:D5), to latch the input data.
• Optionally, if daisy-chaining another 74HC165 for more inputs, connect 74HC165 Pin 9 (Serial Input, SER) to the Q7 of the preceding register.

• Connect each tachometer output from the CPU fans to the parallel inputs of one or more 74HC165 shift registers. Given an 8-fan setup, you would use the parallel inputs D0 to D7 (74HC165 Pins 3 to 7 and Pins 10 to 13) for one 74HC165. If you are measuring more fans, daisy-chain another 74HC165 and continue accordingly.

• To read the fans' tachometer signals, first, you have to latch the current state of all parallel inputs into the shift register's memory. This is done by momentarily setting the Load pin low and then high again.

• After latching the data, you will clock out the bits by toggling the Clock pin. Each toggle of the Clock pin shifts out one bit from the shift register's serial output, which can be read by the ESP32.

• Read the bit from the shift register's serial output after each clock cycle. Repeat for the number of inputs you have latched (8 in this case for one register, more if daisy-chained).

• Connect ESP32 D4 (pin 6) through a transistor to control Fan 1.
• Connect ESP32 D5 (pin 7) through a transistor to control Fan 2.
• ... and so on, for all eight fans. Ensure you choose GPIO pins that support PWM (which is most of them on the ESP32).

• Connect Fan 1 tachometer output to ESP32 D12 (pin 8) with a pull-up resistor.
• Connect Fan 2 tachometer output to ESP32 D13 (pin 9) with a pull-up resistor.
• ... and repeat for all eight fans.