Custom samd21g board I2C device not found

[gamera]

Hello everyone!

I have encountered an unfortunate problem with my custom board, which has the ATSAMD21G18A microcontroller. I am trying to connect the ATECC508A chip via I²C, but it simply won't be recognized.

I have 4.7kΩ pull-up resistors on the SDA and SCL lines, so theoretically, everything should be fine. Unfortunately, I have no communication with the ATECC508A.

I have tried different bootloaders, but none of them were successful, and I have also changed the address in the libraries (0x60).

I'm using a regular I²C scanner code:

#include <Wire.h>

void setup() 
{
  Wire.begin();
  SerialUSB.begin(9600);
  while (!SerialUSB); // Wait for Serial to be ready
  SerialUSB.println("\nI2C Scanner");
}

void loop() 
{
  byte error, address;
  int nDevices;

  SerialUSB.println("Scanning...");

  nDevices = 0;
  for (address = 1; address < 127; address++ ) 
  {
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0) 
    {
      SerialUSB.print("I2C device found at address 0x");
      if (address < 16)
        SerialUSB.print("0");
      SerialUSB.print(address, HEX);
      SerialUSB.println(" !");

      nDevices++;
    } 
    else if (error == 4) 
    {
      SerialUSB.print("Unknown error at address 0x");
      if (address < 16)
        SerialUSB.print("0");
      SerialUSB.println(address, HEX);
    }
  }
  
  if (nDevices == 0)
    SerialUSB.println("No I2C devices found\n");
  else
    SerialUSB.println("done\n");

  delay(5000); // Wait 5 seconds for next scan
}

I also attach screenshots of the schematic, the board was manufactured at PCBWay.

[Railroader]

Here's a link to a dahtasheet I found:

Datasheet for ATECC508A-MAHDA-T Microchip EEPROM | Octopart

I see no CPAD, only NC, no connection. Test removing it!

[markd833]

@gamera might be using the the super small 2mm x 3mm (UDFN?) package version of the ATECC508A. The Microchip datasheet says that the centre pad under the chip should be connected to 0V, which I think is what the CPAD pin might be.

My eyeballs can't quite comprehend a central pad under something as small as 2mm x 3mm! With something that size, I'd have to order 10 of them to allow for at least 6 or 7 falling off the table, ending up hidden in the carpet, never to be seen again.

[gamera]

I’m exactly using the UDFN 2x3mm ATECC508A-MAHCZ-T chip.
I honestly too can’t imagine soldering such a tiny component myself, but I had PCBWay assemble the board. I actually have a second identical board, so tomorrow I’ll try uploading the I2C scanner to that one. However, I believe the CPAD is properly connected to ground