ESP32 C3

Cheap ESP32 C3 module from AliExpress

The Arduino IDE needs the Tools option 'USB CDC On Boot' enabled so the the USB serial works.

ESP32 C3 OLED

Cheap ESP32 C3 module from AliExpress with 72x40 OLED SSD1306

Using the U8g2 library I needed this for a minimal display test:

#include <Wire.h>
#include <Arduino.h>
#include <U8x8lib.h>

// for ESP32 C3 OLED
#define SDA 5
#define SCL 6

U8X8_SSD1306_72X40_ER_HW_I2C u8x8(/* reset=*/ U8X8_PIN_NONE);   // EastRising 0.42"


void setup(void)
{
  Wire.begin(SDA,SCL);
  u8x8.begin();
  u8x8.setPowerSave(0);
}

void loop(void)
{
  // 72x40 gives 9 characters per line with 5 lines
  u8x8.setFont(u8x8_font_chroma48medium8_r);
  u8x8.drawString(0,1,"  Hello");
  u8x8.setInverseFont(1);
  u8x8.drawString(0,0,"012345678");
  u8x8.setInverseFont(0);
  u8x8.refreshDisplay();
  delay(2000);
}

ESP32 C3 with dual USB type C

Has a WS2812 RGBW LED on pin 8