ESP32-C3

What is the ESP32-C3?

The ESP32-C3 is a low-cost Wi-Fi + Bluetooth 5 LE microcontroller (SoC) from Espressif. It is the first chip of the “C” series and the first Espressif chip built on the open RISC-V instruction set instead of Xtensa.

Think of it as the modern replacement for the ESP8266: similar price and size, but with Bluetooth LE, a faster 32-bit core, 400 KB of RAM, hardware security and a USB port that can program and debug the chip directly. It gives up a few things compared with the original ESP32 — one core instead of two, fewer GPIOs, no touch pins and no DAC — which keeps it small, cheap and efficient.

A typical ESP32-C3 dev board: the MINI-1 module holds the chip, flash and antenna; the rest powers it and connects it to your PC.

Inside the ESP32-C3: a RISC-V SoC

A RV32IMC RISC-V core at 160 MHz sits next to generous memory, a shared Wi-Fi/BLE radio, security hardware and a compact set of peripherals, all connected through a GPIO matrix.

Inside the ESP32-C3: CPU, memory and radio at the top, the GPIO matrix in the middle, peripherals and security below.

• RISC-V CPU — open instruction set (RV32IMC: integer, multiply/divide, compressed instructions). Your Arduino code runs unchanged; the compiler handles the difference.
• Memory — 400 KB SRAM (16 KB of it acts as flash cache), 384 KB ROM, and 8 KB RTC memory that survives deep sleep.
• Radio — one 2.4 GHz radio shared by Wi-Fi 802.11 b/g/n and Bluetooth 5 LE, which can run together.
• Security — secure boot, flash encryption, AES/SHA/RSA accelerators, HMAC and a digital-signature peripheral for safe cloud connections.
• What's missing — no touch sensor, no DAC and no ULP coprocessor. Keep that in mind when porting ESP32 projects.

ESP32-C3 Modules and Dev Boards

Espressif sells the chip in certified modules, and makers love tiny boards such as the Seeed XIAO ESP32C3 and the ESP32-C3 SuperMini.

The four common ESP32-C3 modules — “U” versions swap the PCB antenna for an IPEX socket.

Tiny boards label their pins differently, but the GPIO numbers are the same chip pins — always use the GPIO map below.

Full ESP32-C3 GPIO Pinout

Every ESP32-C3 board exposes the same 22 chip GPIOs. This map shows each one with its ADC channel, JTAG, SPI, I2C, USB, UART, flash and strapping roles.

All 22 ESP32-C3 GPIOs and their functions. Left: GPIO0–10. Right: GPIO11–21.

Here are the same pins as a quick colour-coded strip:

GPIO0–21 at a glance — GPIO11–17 belong to the flash, leaving about 15 pins for you.

Every Pin Explained

With only 22 GPIOs, it pays to know exactly what each one does.

Power & control pins (on dev boards)

• 5V — 5 V from USB, or a 5 V input into the on-board LDO.
• 3V3 — regulated 3.3 V for sensors (or a clean 3.3 V input if you skip USB).
• GND — ground.
• RST / EN — chip enable; pull LOW to reset.

USB Serial/JTAG — Program and Debug with One Cable

The C3 has a built-in USB Serial/JTAG controller on GPIO18 (D−) and GPIO19 (D+). It appears on your PC as a serial port and a JTAG debugger — no CP2102 or CH340 required.

Bridge chip or built-in USB: the C3 can do both. The built-in port gives serial + JTAG, not HID.

• Serial Monitor — in Arduino set Tools → USB CDC On Boot → Enabled so Serial goes over the native port.
• Debugging — OpenOCD and the Arduino IDE 2 debugger can single-step code through the same cable.
• Not OTG — it cannot pretend to be a keyboard, mouse or flash drive. For that, choose the ESP32-S2 or ESP32-S3.

Strapping Pins and Boot Modes

At reset the ESP32-C3 reads GPIO2, GPIO8 and GPIO9 to decide how to start.

GPIO9 picks the boot mode; GPIO8 and GPIO2 must stay HIGH. BOOT + RST forces download mode by hand.

Powering the ESP32-C3

The chip needs 3.0–3.6 V. Dev boards take 5 V from USB or the 5V pin and drop it to 3.3 V with an LDO regulator.

USB or 5V pin → LDO → 3.3 V rail. Radio transmit bursts need a solid supply.

• Radio peaks — Wi-Fi transmit pulls short bursts of a few hundred mA; weak cables cause brown-out resets.
• Batteries — a Li-ion cell needs a low-dropout regulator or a buck/buck-boost converter for a steady 3.3 V. The XIAO ESP32C3 even has a charger built in.
• Decoupling — place 10 µF + 100 nF capacitors next to the 3V3 pin on custom boards.

Sleep Modes and Wake Sources

In deep sleep the C3 keeps only its RTC timer and 8 KB of RTC memory alive, drawing just a few microamps.

From active to deep sleep. Wake with the timer or a level on GPIO0–5.

• Deep sleep restarts the program from setup() on wake; save counters in RTC_DATA_ATTR variables.
• GPIO wake uses esp_deep_sleep_enable_gpio_wakeup() and works on GPIO0–5 only.
• Light sleep keeps RAM and wakes in microseconds — good for BLE devices that must answer quickly.

ADC — Analog Input

The ESP32-C3 has a 12-bit ADC (0–4095). Use the five ADC1 channels on GPIO0–4.

ADC1 on GPIO0–4 is the one to use; ADC2 on GPIO5 is not recommended.

• analogRead(pin) returns 0–4095; analogReadMilliVolts(pin) returns a calibrated voltage.
• At maximum attenuation the useful range is about 0–2.5 V, not 3.3 V — use a resistor divider for higher voltages.
• No DAC on the C3: for an analog-style output use PWM with an RC low-pass filter.

PWM with the LEDC Controller

The LEDC peripheral gives 6 PWM channels that the GPIO matrix can route to almost any output pin.

Six PWM channels — enough for an RGB LED, a servo and a motor at the same time.

• ledcAttach(pin, freq, bits) then ledcWrite(pin, duty) (Arduino-ESP32 3.x); analogWrite() also works.
• frequency × 2^bits must stay below the 80 MHz clock — e.g. 5 kHz at 8-bit, or 20 kHz at 10-bit.

UART, I2C, SPI, I2S, TWAI & RMT

The C3 has a compact but complete set of buses, and the GPIO matrix lets you move most of them.

Arduino defaults: UART0 20/21, I2C 8/9, SPI 4–7 — most can be moved with begin(pins).

Wi-Fi on the ESP32-C3

The C3 speaks 2.4 GHz 802.11 b/g/n as a station, an access point, or both, using the same WiFi.h library as every ESP32.

Station, access point or both — and Wi-Fi can run alongside BLE.

Supports WPA3, ESP-NOW, OTA updates, mDNS, WebServer, HTTPClient and TLS — and it is a favourite chip for ESPHome and Home Assistant devices.

Bluetooth 5 LE

The C3 supports Bluetooth 5 Low Energy, so it can talk straight to phones, beacons and BLE sensors.

The C3 as a BLE server: a service holding characteristics the phone can read, write or subscribe to.

• BLE 5 features — 2 Mbps PHY, Coded PHY long range, advertising extensions and mesh.
• Libraries — the built-in BLEDevice library or the lighter NimBLE-Arduino.
• No Bluetooth Classic — for audio (A2DP) or SPP serial, use the original ESP32.

Programming the ESP32-C3

Use the Arduino IDE, Espressif's ESP-IDF, MicroPython, ESPHome or Rust.

1. Arduino IDE → Boards Manager → install esp32 by Espressif Systems.
2. Select ESP32C3 Dev Module (or your board, e.g. XIAO_ESP32C3) and the port.
3. Board without a bridge chip? Set USB CDC On Boot → Enabled.
4. Click Upload. If nothing happens: hold BOOT, tap RST, release BOOT, upload, then press RST.

Code Examples

Short, copy-paste Arduino sketches for the main ESP32-C3 features.

1. Blink an LED on GPIO3

const int LED = 3;                     // LED + 220 Ω to GND
void setup() { pinMode(LED, OUTPUT); }
void loop() {
  digitalWrite(LED, HIGH); delay(500);
  digitalWrite(LED, LOW);  delay(500);
}

2. Cycle the on-board RGB LED (GPIO8)

void setup() {}
void loop() {
  rgbLedWrite(8, 64, 0, 0);  delay(500);   // red   (Arduino-ESP32 3.x)
  rgbLedWrite(8, 0, 64, 0);  delay(500);   // green
  rgbLedWrite(8, 0, 0, 64);  delay(500);   // blue
}

3. Scan for Wi-Fi networks

#include <WiFi.h>
void setup() { Serial.begin(115200); WiFi.mode(WIFI_STA); }
void loop() {
  int n = WiFi.scanNetworks();
  for (int i = 0; i < n; i++)
    Serial.printf("%-24s %4d dBm\n", WiFi.SSID(i).c_str(), WiFi.RSSI(i));
  Serial.println();
  delay(5000);
}

4. Read the ADC in millivolts

void setup() { Serial.begin(115200); }
void loop() {
  int raw = analogRead(1);            // GPIO1 = ADC1_CH1, 0..4095
  int mv  = analogReadMilliVolts(1);  // calibrated
  Serial.printf("raw=%d  %d mV\n", raw, mv);
  delay(200);
}

5. Deep sleep, wake on a button (GPIO3)

RTC_DATA_ATTR int wakes = 0;          // kept in RTC memory
void setup() {
  Serial.begin(115200);
  delay(1000);
  Serial.printf("Wake number %d\n", ++wakes);
  pinMode(3, INPUT_PULLUP);             // button GPIO3 to GND
  esp_deep_sleep_enable_gpio_wakeup(1ULL << 3, ESP_GPIO_WAKEUP_GPIO_LOW);
  esp_deep_sleep_start();
}
void loop() {}

Beginner Mini-Projects

Four small builds that use the C3's strengths: Wi-Fi, BLE and low power.

Wiring for the projects — LED + 220 Ω on GPIO3, button on GPIO10, pot on GPIO1. Other LED values: LED resistor calculator.

bool lampOn = true, lastBtn = HIGH;

void setup() {
  pinMode(10, INPUT_PULLUP);
  ledcAttach(3, 5000, 8);               // 5 kHz, 8-bit PWM on GPIO3
}
void loop() {
  bool btn = digitalRead(10);
  if (lastBtn == HIGH && btn == LOW) lampOn = !lampOn;   // toggle on press
  lastBtn = btn;
  int mv = analogReadMilliVolts(1);       // ~0..2500 mV
  int duty = constrain(mv * 255 / 2500, 0, 255);
  ledcWrite(3, lampOn ? duty : 0);
  delay(20);
}

#include <WiFi.h>
#include <WebServer.h>
WebServer server(80);

void setup() {
  Serial.begin(115200);
  pinMode(3, OUTPUT);
  WiFi.begin("MySSID", "password");
  while (WiFi.status() != WL_CONNECTED) delay(500);
  server.on("/",    []() { server.send(200, "text/html", "<a href='/on'>ON</a> | <a href='/off'>OFF</a>"); });
  server.on("/on",  []() { digitalWrite(3, HIGH); server.send(200, "text/plain", "LED ON"); });
  server.on("/off", []() { digitalWrite(3, LOW);  server.send(200, "text/plain", "LED OFF"); });
  server.begin();
  Serial.println(WiFi.localIP());
}
void loop() { server.handleClient(); }

#include <BLEDevice.h>
#include <BLEServer.h>

class LedCallback : public BLECharacteristicCallbacks {
  void onWrite(BLECharacteristic *c) {
    String v = c->getValue();             // Arduino-ESP32 3.x returns String
    if (v.length()) digitalWrite(3, v[0] == '1' ? HIGH : LOW);
  }
};

void setup() {
  pinMode(3, OUTPUT);
  BLEDevice::init("ESP32-C3 LED");
  BLEServer *server = BLEDevice::createServer();
  BLEService *svc = server->createService("19B10000-E8F2-537E-4F6C-D104768A1214");
  BLECharacteristic *ch = svc->createCharacteristic("19B10001-E8F2-537E-4F6C-D104768A1214",
      BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_WRITE);
  ch->setCallbacks(new LedCallback());
  svc->start();
  BLEDevice::getAdvertising()->addServiceUUID("19B10000-E8F2-537E-4F6C-D104768A1214");
  BLEDevice::startAdvertising();
}
void loop() { delay(1000); }

RTC_DATA_ATTR int readings = 0;

void setup() {
  Serial.begin(115200);
  delay(1000);
  int mv = analogReadMilliVolts(1);     // GPIO1 = ADC1_CH1
  Serial.printf("Reading %d: %d mV\n", ++readings, mv);
  esp_sleep_enable_timer_wakeup(30ULL * 1000000);
  esp_deep_sleep_start();               // a few µA until the next wake
}
void loop() {}

ESP32-C3 vs ESP32 vs ESP32-S2 vs ESP32-S3

All four chips do 2.4 GHz Wi-Fi at 3.3 V; they differ in core, Bluetooth, USB and pin count.

The ESP32 family side by side.

• Pick the ESP32-C3 for the cheapest Wi-Fi + BLE 5 node, ESPHome devices and ESP8266 upgrades.
• Pick the original ESP32 for two cores, touch, DAC or Bluetooth Classic audio.
• Pick the ESP32-S2 for USB HID/MSC gadgets when Bluetooth isn't needed.
• Pick the ESP32-S3 for cameras, AI/vector maths, USB OTG and BLE 5 together.

Specifications

The ESP32-C3 at a glance.

Key ESP32-C3 numbers: CPU, memory, radio, USB, GPIO, analog, buses, low power and security.

Key Terms — Glossary

Related Topics & Common Searches

Keep building your microcontroller and electronics knowledge with these Power4All guides:

People Also Search For

esp32-c3 · esp32-c3 pinout · esp32 c3 gpio · esp32-c3 datasheet · esp32-c3 risc-v · esp32-c3 vs esp32 · esp32-c3 vs esp32-s3 · esp32-c3 vs esp8266 · esp32-c3 ble example · esp32-c3 bluetooth classic · esp32-c3 devkitm-1 pinout · xiao esp32c3 pinout · esp32-c3 supermini pinout · esp32-c3 rgb led gpio8 · esp32-c3 strapping pins · esp32-c3 boot button gpio9 · esp32-c3 not detected · esp32-c3 usb cdc on boot · esp32-c3 usb serial jtag · esp32-c3 adc pins · esp32-c3 adc2 · esp32-c3 pwm · esp32-c3 i2c pins · esp32-c3 spi pins · esp32-c3 deep sleep current · esp32-c3 gpio wakeup · esp32-c3 arduino ide · esp32-c3 micropython · esp32-c3 esphome · esp32-c3 web server · esp32-c3 projects · esp32-c3 5v tolerant.

Frequently Asked Questions

Quick answers to the questions people ask most about the ESP32-C3.

Conclusion & Key Takeaways

The ESP32-C3 packs Wi-Fi, Bluetooth 5 LE, a modern RISC-V core and USB debugging into a tiny, cheap chip — the natural choice for connected sensors, smart-home gadgets and anyone upgrading from the ESP8266.

Continue Learning