17 thoughts on “ESP32-S3 DevKitC Pinout Refence Guide: GPIOs Explained”

1. If pin GPIO 8 (SDA) , GPIO 9 (SCL) are occupied it is possible to use some other pins fo I2C?
   Thanks
   Renzo

   Reply

   • Hi Sara,
     Thank you very much for this short tutorial.
     I have the exact questions Boris request.
     Using the 16MB Flash would really be great.

     For Renzo,
     Try some variant of the following code to redefine I2C pins for any ESP32.

     The following code can be used to redefine I2C & reads an analog signal using an I2C device, The analog signal on pin A0 of the ADS1115 is from a light sensor that detects a laser pulse at high resolution.
     The ADS1115 is an I2C device with 16 bit resolution and a multiplexed 4 channel Analog to Digital Converter.
     Adafruit has some excellent info on how to use and on programmable gain for the ADS1115.
     Note that the 20 ADC channels on ESP32 are 12 bit.
     Also the following code does not include all the initialization for the variables, or all the calls, or all the functions.
     It is hoped that it will help illustrate the concepts for redefining I2C pins, etc.)

     // Include the I2C library
     #include <Wire.h>

     // Include a library for the I2C device, for example an I2C using a 16bit ADC
     #include <Adafruit_ADS1X15.h>

     // Define I2C pins
     #define SDA_PIN 21 // Replace with your desired SDA pin
     #define SCL_PIN 22 // Replace with your desired SCL pin

     Adafruit_ADS1115 ads; // Create an instance of the ADS1115 ADC
     const int analogInputPin = 0; // Initialize the A0 pin on ADS1115 device

     // Initialize global variables
     const int numSamplesForBaseline = 100;
     const int numSamplesPerPulse = 10;
     unsigned long previousMicros = 0;
     unsigned long sampleIntervalMicros = 500;
     int baselineThreshold = 0;
     int analogSum = 0;
     int pulseCount = 0;
     int averageAmplitude = 0;

     void setup() {
     Serial.begin(115200);
     Wire.begin(SDA_PIN, SCL_PIN); // Initialize I2C w specified SDA & SCL pins
     ads.begin();

     // Calculate baseline threshold during initialization
     calculateBaselineThreshold();

     // Insert other code for setup

     }

     void loop() {
     // Read and process analog signal
     processAnalogSignal(currentMicros);

     // Main loop code Example: Print results every 10 seconds
     if (currentMicros – previousMicros >= 10000000) {
     printResultsToSerial();
     sendResultsToThingSpeak();
     previousMicros = currentMicros;
     }

     }

     void processAnalogSignal(unsigned long currentMicros) {
     int rawAnalogValue = ads.readADC_SingleEnded(analogInputPin);
     baselineThreshold = (baselineThreshold + rawAnalogValue) / 2;

     if (rawAnalogValue > baselineThreshold) {
     if (currentMicros – previousMicros >= sampleIntervalMicros) {
     for (int i = 0; i < numSamplesPerPulse; i++) {
     rawAnalogValue = ads.readADC_SingleEnded(analogInputPin);
     analogSum += rawAnalogValue;
     }

     averageAmplitude = analogSum / numSamplesPerPulse;
analogSum = 0;
pulseCount++;
previousMicros = currentMicros;
}


     }
     }

     void printResultsToSerial() {
     Serial.println(“Average Amplitude: ” + String(averageAmplitude));
     Serial.println(“Pulse Count: ” + String(pulseCount));
     }

     Best regards,
     Joe

     Reply

   • Hi Renzo,
     Random Nerds has a great I2C tutorial at
     https://randomnerdtutorials.com/esp32-i2c-communication-arduino-ide/
     It shows how to redefine ESP32 pins for I2C.
     Best regards,
     Joe

     Reply

2. Hello guys!!

   I got the exact same board. I would really appreciate a tutorial on how to use the full 16mb flash memory.
   I tried a lot of things but I never could use more than 3.5mb something no matter what settings I selected in the Arduino IDE.

   Have a great day!!

   Boris

   Reply

   • I have the same problem. Tried about everything I could find on the Web to no avail. Would really like a tutorial on that.

     Thanks in advance.
     Frank

     Reply

3. Should MOSI of HSPI (SPI 2) not be GPIO11 instead of GPIO35?

   Reply

   • Yes. You’re right.
     It’s fixed now.
     Regards,
     Sara

     Reply

4. Why don’t you guys make projects using ESP-IDF? Your step by step guide will be really helpful for others.

   Reply

5. Many questions come up to mind, I guess most of your projects should be reviewed using this board, especially the ones about memery management and usage of sd cards. Thank you for this first coverage of this board.

   Reply

6. Does anyone has an idea about how to achieve debugging with this board because it has this dedicated usbc port for this purpose.

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7. I have been using this exact DevKit, a true Espressif version, not one of the countless variations, for over a year and have discovered via much frustration that some of the pin-outs you list are not correct or should be avoided, at least with MicroPython firmware. You should not/cannot use TX0/RX0, HSPI is GPIO9-11, GPIO48 is the RGB led, and GPIO35-37 can be used on the N8 variant (no PSRAM) but not on the N8R8 variant (with PSRAM).

   Reply

   • Hi.
     Thanks for your feedback.
     I’ll that a look into that.
     Regards,
     Sara

     Reply

8. I2C: When using the ESP32-S3 with the Arduino IDE, these are the ESP32 I2C default pins: GPIO 8 (SDA) & GPIO 9 (SCL)

   THANK YOU! I have been trying to find the default GPIO pin numbers for BOTH of the ESP32-S3 default built-in I2C ports (four pins total) for days on end. And here you have two of the four, and I tested them both with an I2C scanner utility, and they work!

   Is there any way you can provide the GPIO pin numbers for the second default I2C port on the ESP32-S3-DevKitC-1 board? I do not have the ESP-IDF installed so I cannot snoop around in source and header files. And of-course the ESP documentation does not list the GPIO numbers, at least I can’t find them.

   Thank You, David in Florida

   Reply

9. Here is how I scanned one default I2C port on the ESP32-S3-DevKitC-1 board to verify the I2C port works with Rui’s GPIO numbers:

   /**********************************
   ESP32-S3 I2C Scanner v1.01.txt
   ESP32-S3 I2C Scanner
   OLED ESP32-S3
   +———-+ +———-+
   | GND|—-|GND |
   | VCC|—-|3V3 |
   | SCL|—-|GPIO9 |
   | SDA|—-|GPIO8 |
   +———-+ +———-+

   Posted by Rui Santos: https://randomnerdtutorials.com/esp32-s3-devkitc-pinout-guide/
   I2C: When using the ESP32-S3 with the Arduino IDE, these are the ESP32 I2C default pins:

   GPIO 8 (SDA)

   GPIO 9 (SCL)

   Select these two pins like this in your sketch:
   //Wire.begin(I2C_SDA, I2C_SCL);
   Wire.begin(8, 9);

   Serial Monitor says (this is a 0.96″ I2C OLED SSD1306 display):
   Scanning…
   I2C device found at address 0x3C

   Hardware:
   ESP32-S3-DevKitC-1: https://www.amazon.com/dp/B0D9W4Y3F3
   0.96″ White SSD1306 I2C OLED Display: https://www.amazon.com/dp/B09T6SJBV5

   Problem: The onboard addressable RGB LED on GPIO38 is always
   on bright white. I cannot find a way to simply disable it in software.

   **********************************/

   #include <Wire.h>

   #define rgbledPin 38

   void setup() {
   //Wire.begin(I2C_SDA, I2C_SCL);
   Wire.begin(8, 9); //For ESP32-S3-DevKitC-1 board
   //Wire.begin(5, 4);
   //Wire.begin(33, 32);
   pinMode(rgbledPin, OUTPUT);
   //pinMode(rgbledPin, INPUT);
   Serial.begin(115200);
   Serial.println(“\nI2C Scanner Started…”);
   }

   void loop() {
   byte error, address;
   int nDevices;
   Serial.println(“Scanning…”);
   digitalWrite(rgbledPin, LOW);
   //digitalWrite(rgbledPin, HIGH);
   nDevices = 0;
   for(address = 1; address < 127; address++ ) {
   Wire.beginTransmission(address);
   error = Wire.endTransmission();
   if (error == 0) {
   Serial.print(“I2C device found at address 0x”);
   if (address<16) {
   Serial.print(“0”);
   }
   Serial.println(address,HEX);
   nDevices++;
   }
   else if (error==4) {
   Serial.print(“Unknow error at address 0x”);
   if (address<16) {
   Serial.print(“0”);
   }
   Serial.println(address,HEX);
   }
   }
   if (nDevices == 0) {
   Serial.println(“No I2C devices found\n”);
   }
   else {
   Serial.println(“done\n”);
   }
   //digitalWrite(ledPin, LOW);
   delay(2000);
   }

   Reply

10. You can actually use any (more or less) pins for I2C with the ESP32-S3. Micropython allows you to specify them. I don’t know if the Arduino platform also does. I strongly recommend you wean yourself from Arduino and use Micropython instead. One of the smartest moves I ever made.

    Reply

11. Did this research so time ago as well but it seems there are no default pins for the second I2C interface.

    Here is how you can define custom pins for I2C in Arduino IDE:

    int sda_pin = 6; // GPIO6 as I2C SDA
    int scl_pin = 7; // GPIO7 as I2C SCL

    void setup()
    {
    Wire.setPins(sda_pin, scl_pin); // Set the I2C pins before begin
    Wire.begin(); // join i2c bus (address optional for master)
    }

    It’s important to call “Wire.setPins()” before “Wire.begin()”.

    docs.espressif.com/projects/arduino-esp32/en/latest/tutorials/io_mux.html

    Reply

    • Thanks for sharing this info.
      Regards,
      Sara

      Reply