ESP32 not able to detect any I2C devices

Question

I am trying my hand at building a smart watch from scratch. I just got the latest PCBs delivered and upon soldering everything I found that the TTGO micro-32, essentially an ESP32, cannot detect any of the sensors over I2C. (The linked datasheet is the most detailed one I can find). I currently have 4.7 kΩ pull-up resistors tying SCL and SDA to 3.3 V which is also the operating voltage of the TTGO.

However, I initially tried 1 kΩ pull-up resistors with no success either. I also tried removing the pull-up resistors completely because I figured the TTGO probably had internal pull-ups like the ESP32, but that did not work.

The sensors I am using are the BME680, MCP79402T-I/MS (RTC), and ADXL345BCCZ-RL7 (Accelerometer).

Below is the schematic for the design:

I found the TTGO cannot detect the sensors by running this I2C scanner code within the Arduino compiler:

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

void setup()
{
  Wire.begin(21, 22);
  Serial.begin(115200);
  while (!Serial);             
  Serial.println("\nI2C Scanner");
}

void loop()
{
  byte error, address;
  int nDevices;
  Serial.println("Scanning...");
  nDevices = 0;
  for(address = 1; address < 127; address++ )
  {
    // The i2c_scanner uses the return value of
    // the Write.endTransmisstion to see if
    // a device did acknowledge to the 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.print(address,HEX);
      Serial.println("  !");
      nDevices++;
     }
     else if (error==4)
     {
      Serial.print("Unknown 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");
    delay(5000);           // wait 5 seconds for next scan
}

Here is where it gets confusing though. Before I designed this board, I created a breakout board for the TTGO micro-32 and wired a 128x64 OLED module to it via I2C.

I ran the same code on the breakout board to find the I2C address of the screen and it worked. For reference, on the breakout I did not use any pull-up resistor because from the best I can tell the screen has 4.7 kΩ pull-ups on it already. I have no idea what the problem could be since from the best I can tell my schematic matches the datasheets and it isn't a software issue.

Answer 1

one can find I2C devices on an ESP32 using the code below:

  void I2Cscanner() {
  Serial.println ();
  Serial.println ("I2C scanner. Scanning ...");
  byte count = 0;

  Wire.begin();
  for (byte i = 8; i < 120; i++)
  {
    Wire.beginTransmission (i);          // Begin I2C transmission Address (i)
    if (Wire.endTransmission () == 0)  // Receive 0 = success (ACK response) 
    {
      Serial.print ("Found address: ");
      Serial.print (i, DEC);
      Serial.print (" (0x");
      Serial.print (i, HEX);     // PCF8574 7 bit address
      Serial.println (")");
      count++;
    }
  }
  Serial.print ("Found ");      
  Serial.print (count, DEC);        // numbers of devices
  Serial.println (" device(s).");
}