ESP32-C3 SuperMini Overview

The board exposes GPIO0 to GPIO10 plus GPIO20 and GPIO21 on its two rows of pads. GPIO18 and GPIO19 are used internally by the ESP32-C3 native USB interface and are not brought out on this SuperMini layout.

Powering the Board

For normal development, power and program the board through its USB-C connector using a data-capable USB cable.

WiFi transmission can cause short current peaks, so use a stable supply and keep power wiring reasonably short. Do not assume the 3.3V pin can power motors, relays or other high-current loads.

Pinout & GPIO Functions

BOOT and RESET Buttons

The RESET button restarts the ESP32-C3. The BOOT button is connected to GPIO9 and is used to force the chip into its ROM download mode when automatic USB uploading does not work.

To enter download mode manually:

1. Press and hold BOOT.
2. Press and release RESET.
3. Release BOOT.
4. Select the newly detected port in Arduino IDE and upload again.

Arduino IDE Setup

No additional library is required for the basic LED, WiFi or I2C examples in this guide. These features are included with the Espressif Arduino-ESP32 core.

1. Install ESP32 Support

Install a current Arduino IDE, then open the IDE preferences and add the following stable Espressif Boards Manager URL:

https://espressif.github.io/arduino-esp32/package_esp32_index.json

Open Tools > Board > Boards Manager, search for esp32, then install esp32 by Espressif Systems.

2. Select the Board

Select:

• Tools > Board > ESP32 Arduino > ESP32C3 Dev Module
• USB CDC On Boot > Enabled
• Tools > Port and choose the port belonging to the ESP32-C3

3. Connect a Data-Capable USB Cable

Some USB-C cables provide power only. A board that lights its power LED but never appears as a USB device may simply be connected with a charge-only cable.

Basic Test – Onboard LED

The supplied board has a blue user LED connected to GPIO8. It is active-low, which means writing LOW turns the LED on and writing HIGH turns it off.

const int LED_PIN = 8;

void setup() {
  Serial.begin(115200);

  pinMode(LED_PIN, OUTPUT);

  // GPIO8 LED is active-low.
  digitalWrite(LED_PIN, HIGH);

  delay(1000);
  Serial.println("ESP32-C3 SuperMini LED test started");
}

void loop() {
  digitalWrite(LED_PIN, LOW);
  Serial.println("LED ON");
  delay(1000);

  digitalWrite(LED_PIN, HIGH);
  Serial.println("LED OFF");
  delay(1000);
}

Expected Result

After uploading, the blue onboard LED should turn on for one second and off for one second repeatedly. Open Serial Monitor at 115200 baud to see matching LED ON and LED OFF messages.

If the upload succeeds but the program does not start, press the RESET button once.

WiFi Proof-of-Operation Test

The following sketch scans for nearby 2.4GHz WiFi networks. It does not connect to a network or require a WiFi password.

#include <WiFi.h>

void setup() {
  Serial.begin(115200);
  delay(1000);

  WiFi.mode(WIFI_STA);
  WiFi.disconnect();
  delay(100);

  Serial.println("ESP32-C3 WiFi scanner");
}

void loop() {
  Serial.println();
  Serial.println("Scanning for WiFi networks...");

  int networkCount = WiFi.scanNetworks();

  if (networkCount == 0) {
    Serial.println("No networks found.");
  } else {
    Serial.printf("%d network(s) found:\n", networkCount);

    for (int i = 0; i < networkCount; i++) {
      Serial.printf(
        "%2d: %-32s RSSI %d dBm\n",
        i + 1,
        WiFi.SSID(i).c_str(),
        WiFi.RSSI(i)
      );
    }
  }

  WiFi.scanDelete();
  delay(5000);
}

Expected Result

Serial Monitor should display nearby 2.4GHz WiFi network names and their received signal strengths. Seeing one or more expected local networks confirms that the ESP32-C3 radio and Arduino WiFi support are operating.

Using I2C Devices

The ESP32-C3 can route I2C through its GPIO matrix. Although the supplied pin diagram labels GPIO8 as SDA and GPIO9 as SCL, those two pins also have important board functions. For new projects, explicitly assigning other GPIOs avoids conflicts with the onboard LED and BOOT circuitry.

The following example uses GPIO0 for SDA and GPIO1 for SCL.

#include <Wire.h>

const int SDA_PIN = 0;
const int SCL_PIN = 1;

void setup() {
  Serial.begin(115200);
  delay(1000);

  Wire.begin(SDA_PIN, SCL_PIN);

  Serial.println("ESP32-C3 I2C scanner");
  Serial.println("SDA = GPIO0, SCL = GPIO1");
}

void loop() {
  byte deviceCount = 0;

  Serial.println();
  Serial.println("Scanning I2C bus...");

  for (byte address = 1; address < 127; address++) {
    Wire.beginTransmission(address);
    byte error = Wire.endTransmission();

    if (error == 0) {
      Serial.printf("Device found at 0x%02X\n", address);
      deviceCount++;
    }
  }

  if (deviceCount == 0) {
    Serial.println("No I2C devices found.");
  } else {
    Serial.printf("%u device(s) found.\n", deviceCount);
  }

  delay(5000);
}

Expected Result

With a correctly connected I2C device, Serial Monitor should report one or more hexadecimal addresses such as 0x3C, 0x40 or another address appropriate to the connected device.

Analog Input / ADC Notes

The ESP32-C3 provides six ADC-capable GPIOs on this board:

• GPIO0 – ADC1 channel 0
• GPIO1 – ADC1 channel 1
• GPIO2 – ADC1 channel 2
• GPIO3 – ADC1 channel 3
• GPIO4 – ADC1 channel 4
• GPIO5 – ADC2 channel 0

Arduino-ESP32 uses 12-bit ADC readings by default, giving raw values from 0 to 4095. For voltage measurements, analogReadMilliVolts() can provide a calibrated millivolt result.

WiFi Antenna Considerations

Keep the antenna end of the board away from metal enclosures, large ground planes, batteries and dense wiring where practical. Antenna placement can make a significant difference to WiFi and Bluetooth range.

Troubleshooting