This is additional information to go along with the Halloween eyes / Spooky eyes build I posted on Youtube

https://www.youtube.com/watch?v=VG7mEtcX0hQ

 

The schematic first, with the project config info below this:

And a configuration file showing the required settings for the pins used on the Seeed Xiao MCU, to match the schematic diagram above:

 

// Arduino "Uncanny Eyes" configuration file from the Adafruit project.
//
// Pin selections below modified to suit a Seeed Xiao MCU module,
// wired to Robert Jenkins schematic version.
// Changes or useful options/settings are marked with ++++++
// The pin selection lines need to match the schematic ort whatever wiring is used, 
// the appearance options are up to you - try variations!
//
// GRAPHICS SETTINGS (appearance of eye) -----------------------------------
//
// If using a SINGLE EYE, you might want this next line enabled, which
// uses a simpler "football-shaped" eye that's left/right symmetrical.
// Default shape includes the caruncle, creating distinct left/right eyes.
// Hallowing, with one eye, does this by default
#if defined(ADAFRUIT_HALLOWING) || defined(ARDUINO_SAMD_CIRCUITPLAYGROUND_EXPRESS) || defined(ARDUINO_NRF52840_CIRCUITPLAY)
  #define SYMMETRICAL_EYELID
#else                     // Otherwise your choice, standard is asymmetrical
  //#define SYMMETRICAL_EYELID ++++++
#endif

// Enable ONE of these #includes -- HUGE graphics tables for various eyes:
#include "graphics/defaultEye.h"      // Standard human-ish hazel eye -OR-
//#include "graphics/dragonEye.h"     // Slit pupil fiery dragon/demon eye -OR-
//#include "graphics/noScleraEye.h"   // Large iris, no sclera -OR-
//#include "graphics/goatEye.h"       // Horizontal pupil goat/Krampus eye -OR-
//#include "graphics/newtEye.h"       // Eye of newt -OR-
//#include "graphics/terminatorEye.h" // Git to da choppah!
//#include "graphics/catEye.h"        // Cartoonish cat (flat "2D" colors)
//#include "graphics/owlEye.h"        // Minerva the owl (DISABLE TRACKING)
//#include "graphics/naugaEye.h"      // Nauga googly eye (DISABLE TRACKING)
//#include "graphics/doeEye.h"        // Cartoon deer eye (DISABLE TRACKING)

// Optional: enable this line for startup logo (screen test/orient):
#if !defined(ADAFRUIT_HALLOWING)    // Hallowing can't always fit logo+eye
//  #include "graphics/logo.h"        // Otherwise your choice, if it fits
#endif

// EYE LIST ----------------------------------------------------------------

// This table contains ONE LINE PER EYE.  The table MUST be present with
// this name and contain ONE OR MORE lines.  Each line contains THREE items:
// a pin number for the corresponding TFT/OLED display's SELECT line, a pin
// pin number for that eye's "wink" button (or -1 if not used), and a screen
// rotation value (0-3) for that eye.

eyeInfo_t eyeInfo[] = {
#if defined(ADAFRUIT_HALLOWING)
  { 39, -1, 2 }, // SINGLE EYE display-select and wink pins, rotate 180
#elif defined(ARDUINO_SAMD_CIRCUITPLAYGROUND_EXPRESS) || defined(ARDUINO_NRF52840_CIRCUITPLAY)
  { A6, -1, 2 }, // SINGLE EYE display-select and wink pins, rotate 180
#elif defined(ADAFRUIT_TRINKET_M0)
  {  0, -1, 0 }, // SINGLE EYE display-select, no wink, no rotation
#else
  { 2, -1, 0 }, // LEFT EYE display-select and wink pins, no rotation ++++++
  { 3, -1, 0 }, // RIGHT EYE display-select and wink pins, no rotation ++++++
#endif
};

// DISPLAY HARDWARE SETTINGS (screen type & connections) -------------------

#if defined(ARDUINO_SAMD_CIRCUITPLAYGROUND_EXPRESS)
  #define TFT_SPI        SPI1
  #define TFT_PERIPH     PERIPH_SPI1
#else
  #define TFT_SPI        SPI
  #define TFT_PERIPH     PERIPH_SPI
#endif

#if defined(ADAFRUIT_HALLOWING)
  #include <Adafruit_ST7735.h>  // 128x128 TFT display library
  #define DISPLAY_DC        38  // Display data/command pin
  #define DISPLAY_RESET     37  // Display reset pin
  #define DISPLAY_BACKLIGHT  7
  #define BACKLIGHT_MAX    128
  //#define SYNCPIN         A2  // I2C sync if set, GND this pin on receiver
  //#define SYNCADDR      0x08  // I2C address of receiver
                                // (Try disabling SYMMETRICAL_EYELID then)
#elif defined(ARDUINO_SAMD_CIRCUITPLAYGROUND_EXPRESS) || defined(ARDUINO_NRF52840_CIRCUITPLAY)
  #include <Adafruit_ST7789.h> // 240x240 TFT display library
  #define DISPLAY_DC        A7 // Display data/command pin
  #define DISPLAY_RESET     -1 // Display reset pin
  #define DISPLAY_BACKLIGHT A3
  #define BACKLIGHT_MAX    255
#else
  // Enable ONE of these #includes to specify the display type being used
  //#include <Adafruit_SSD1351.h>  // OLED display library -OR-
  #include <Adafruit_ST7735.h>  // TFT display library (enable one only)
  #if defined(ADAFRUIT_TRINKET_M0)
    #define DISPLAY_DC       1
    #define DISPLAY_RESET   -1 // Use MCU reset pin
  #else
    #define DISPLAY_DC       1  // Data/command pin for ALL displays ++++++
    #define DISPLAY_RESET    0  // Reset pin for ALL displays ++++++
  #endif
#endif

#if defined(_ADAFRUIT_ST7735H_) || defined(_ADAFRUIT_ST77XXH_)
 #if defined(ARDUINO_ARCH_NRF52)
  #define SPI_FREQ 32000000    // TFT: use max SPI
 #else
  #define SPI_FREQ 24000000    // TFT: use max SPI
 #endif
#else // OLED
  #if !defined(ARDUINO_ARCH_SAMD) && (F_CPU <= 72000000)
    #define SPI_FREQ 24000000  // OLED: 24 MHz on 72 MHz Teensy only
  #else
    #define SPI_FREQ 12000000  // OLED: 12 MHz in all other cases
  #endif
#endif

// INPUT SETTINGS (for controlling eye motion) -----------------------------

// JOYSTICK_X_PIN and JOYSTICK_Y_PIN specify analog input pins for manually
// controlling the eye with an analog joystick.  If set to -1 or if not
// defined, the eye will move on its own.
// IRIS_PIN speficies an analog input pin for a photocell to make pupils
// react to light (or potentiometer for manual control).  If set to -1 or
// if not defined, the pupils will change on their own.
// BLINK_PIN specifies an input pin for a button (to ground) that will
// make any/all eyes blink.  If set to -1 or if not defined, the eyes will
// only blink if AUTOBLINK is defined, or if the eyeInfo[] table above
// includes wink button settings for each eye.

//#define JOYSTICK_X_PIN A0 // Analog pin for eye horiz pos (else auto)
//#define JOYSTICK_Y_PIN A1 // Analog pin for eye vert position (")
//#define JOYSTICK_X_FLIP   // If defined, reverse stick X axis
//#define JOYSTICK_Y_FLIP   // If defined, reverse stick Y axis

//#define TRACKING            // If defined, eyelid tracks pupil ++++++


#define AUTOBLINK           // If defined, eyes also blink autonomously
#if defined(ADAFRUIT_HALLOWING)
  #define LIGHT_PIN      A1 // Hallowing light sensor pin
  #define LIGHT_CURVE  0.33 // Light sensor adjustment curve
  #define LIGHT_MIN      30 // Minimum useful reading from light sensor
  #define LIGHT_MAX     980 // Maximum useful reading from sensor
#elif defined(ARDUINO_SAMD_CIRCUITPLAYGROUND_EXPRESS) || defined(ARDUINO_NRF52840_CIRCUITPLAY) // TFT Gizmo
 // #define LIGHT_PIN      A8 // CPX light sensor pin
  #define LIGHT_CURVE  0.33 // Light sensor adjustment curve
  #define LIGHT_MIN      30 // Minimum useful reading from light sensor
  #define LIGHT_MAX     980 // Maximum useful reading from sensor
  #define BLINK_PIN       4 // Pin for manual blink button (BOTH eyes)
  #define PIXEL_DOUBLE      // Use 2x2 pixels on 240x240 display
#elif defined(ADAFRUIT_TRINKET_M0)
  #define BLINK_PIN      -1 // No blink pin
  #define LIGHT_PIN      -1 // No photocell
#else
  #define BLINK_PIN       5 // Pin for manual blink button (BOTH eyes) 
  #define LIGHT_PIN      A4 // Photocell or potentiometer (else auto iris) ++++++
  #define LIGHT_PIN_FLIP    // If defined, reverse reading from dial/photocell
  #define LIGHT_MIN       0 // Lower reading from sensor
  #define LIGHT_MAX    1023 // Upper reading from sensor
#endif
#define IRIS_SMOOTH         // If enabled, filter input from IRIS_PIN
#if !defined(IRIS_MIN)      // Each eye might have its own MIN/MAX
  #define IRIS_MIN      120 // Iris size (0-1023) in brightest light
#endif
#if !defined(IRIS_MAX)
  #define IRIS_MAX      720 // Iris size (0-1023) in darkest light
#endif