ESP32-C3 OLED

By | 2025-03-26
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This microcontroller module is great as it is cheap, but also incorporates an OLED display. I admit, that the screen is extremely small 0.42″, but it can still display some basic information, and you will not buy a screen and the microcontroller for the price of ($6 or 5.6 EUR).

There are at least two variants out there with this name, on mine the buttons are located oppose from the USB connector.

Buy here

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Setting up in PlatformIO

We should use the espressif32 platform with the board of esp32-c3-devkitm-1, however e.g. the LED_BUILTIN is not the same with my board, so this is not the same board layout.

[env:esp32-c3-oled]
platform = espressif32
board = esp32-c3-devkitm-1
framework = arduino
lib_deps =
  olikraus/U8g2

Initial code

Here is a sample code for the module. It of course already tests the screen with the U8g2 library, as it is the star of the show. To list all the peripherals tested:

  • On-board 72×40 OLED screen using hardware i2c,
  • Built in LED on pin 8,
  • Button called “BOOT” on pin 9,
  • ESP32-c3 internal temperature sensor.

(We use some legacy code for the temperature sensing, so it will not work in the future.)

#include <Arduino.h>
#include <U8g2lib.h>
// Legacy library for the temperature sensor
#include "driver/temp_sensor.h"

#include <Wire.h>

#define SDA_PIN 5
#define SCL_PIN 6

#define PIN_LED     8
#define PIN_BUTTON  9

U8G2_SSD1306_72X40_ER_F_HW_I2C u8g2(U8G2_R0, U8X8_PIN_NONE);

void drawText(const char *text)
{
  u8g2.drawStr(0, 0, text);
}

// Initialize the temperature sensor
void initTempSensor(){
  temp_sensor_config_t temp_sensor = TSENS_CONFIG_DEFAULT();
  temp_sensor.dac_offset = TSENS_DAC_L2;
  temp_sensor_set_config(temp_sensor);
  temp_sensor_start();
}

void setup() {
  pinMode(PIN_LED, OUTPUT);
  pinMode(PIN_BUTTON, INPUT);

  Wire.begin(SDA_PIN, SCL_PIN);   
  u8g2.begin();

  u8g2.setDisplayRotation(U8G2_R3); // Rotate the display 180 degrees
  u8g2.setFont(u8g2_font_fub25_tf); // Use high pixel wide font
  u8g2.setDrawColor(1);
  u8g2.setFontPosTop();

  initTempSensor();
}

char buffer[5];

void loop() {
  // Read temperature and convert it to const char*
  float temp_celsius = 0;
  temp_sensor_read_celsius(&temp_celsius);
  snprintf(buffer, sizeof(buffer), "%.0f", temp_celsius);
  const char* buffer_c = buffer;

  u8g2.clearBuffer();
  drawText(buffer_c);
  u8g2.sendBuffer();

  digitalWrite(PIN_LED, digitalRead(PIN_BUTTON));

  delay(100);
}

How to continue

We should also check

  • WiFi and Bluetooth capability