OLED robot eyes generator for Arduino and ESP32

Every mood starts from the same two rounded rectangles. The expression comes from black "eyelids" drawn on top, which is cheap on a small microcontroller and easy to animate because each lid is one number that slides from 0 to its target.

• Neutral is the plain rounded eye. It's the resting face most desk robots return to.
• Happy cuts a large round shape out of the bottom of each eye, leaving the upside-down "smiling" arches.
• Angry drops a triangle on the inner top corner of each eye, so the brows slant down toward the nose.
• Sad or tired mirrors that triangle to the outer corners, so the eyes droop outward.
• Surprised grows the eyes wider and taller. Add pupils and it reads as wide-eyed shock.
• Suspicious closes the top and bottom lids a little for a narrow squint.
• Sleepy lowers a flat top lid over most of each eye. Pair it with a slow blink.
• Love swaps each eye for a heart built from two circles and a triangle.
• Confused makes one eye smaller and the other larger, with a slight brow tilt.

Because moods are numbers, not pictures, a change from angry to happy is a smooth morph rather than a jump cut. It's the detail people notice first when a robot looks alive.

The usual way to animate eyes on an OLED is a stack of bitmaps. A full 128×64 frame is 1,024 bytes, so a smooth blink of eight frames is 8 KB, and a few moods with blinks quickly pass the 32 KB of flash on an Uno. The generated sketch takes another route: it draws two rounded rectangles every frame and cuts the expression out with triangles and rectangles. The whole face is a handful of numbers.

That has three practical benefits. The sketch fits an Uno with room left for sensors, a servo and your own logic. Blinks and glances are continuous, so the eyes can look anywhere rather than at four fixed positions. And you can change the mood from code with one variable, which is what you want when a distance sensor or a button decides how the robot feels.

Bitmaps still have a place when you want hand-drawn detail, like lashes, sparkles or a logo in the pupil. For that, export frames from this tool or draw them in the OLED Animation Maker. My robot eyes tutorial walks through the same geometry by hand if you want to understand every line.

SSD1306 or SH1106?

Most 0.96 inch modules are SSD1306 and most 1.3 inch modules are SH1106. If you pick the wrong one, the SH1106 shows a two-pixel strip of noise on one side and the eyes sit off-centre. Choose SH1106 in the generator and the code switches to the Adafruit SH110X library or the U8g2 SH1106 constructor. If the screen stays dark, try address 0x3D instead of 0x3C.

Tips for 128×32 bar displays

A 0.91 inch 128×32 OLED is only 32 pixels tall, so the generator caps the eye height when you choose it. Wide, short eyes with a radius of 4 to 6 read best, and a look-around range of 2 to 3 pixels up and down keeps them on the glass. Sleepy and happy still work well. Surprised has less room to grow.

One eye per screen

For bigger eyes, use two OLEDs. Generate one-eye (cyclops) code, put the second module on address 0x3D, and draw once per display with the gaze mirrored for the right eye. My guide to two OLED displays on one Arduino covers the address jumper and the wiring, and the ESP32 OLED animation guide covers faster I2C for smoother motion.

The rounded, pupil-less look of popular desk robots is the Round desk robot preset: two soft squares, a small gap and quick blinks. On its own it already feels alive. Adding one input makes it feel aware.

• Touch: a TTP223 touch pad on any digital pin. Enter the pin in the generator and a tap makes the eyes happy for two seconds.
• Head movement: a small SG90 servo. Read gx, the current gaze, and turn the servo the same way so the head follows the eyes.
• Distance: an ultrasonic or ToF sensor. Set overrideMood = SURPRISED; when something gets close, and back to -1 when it leaves.
• Sound: a microphone module. A loud clap can trigger a blink with blinking = true; blinkStart = millis();.
• Time: after 30 seconds without input, switch to sleepy. It's a simple timer and people love it.

Power the servo from its own 5 V supply and share ground. A servo pulling current from the same rail as the OLED causes flicker and random resets, the most common desk robot bug I see.