When compiling your code, you may come across this error:

error: call of overloaded 'write(int)' is ambiguous

This occurs when the value zero 0 is assigned to the Serial.write() function. 0, NULL and 0x00 can be interpreted as the Null value or an unsigned byte by the Serial.write() function.

This function writes binary data to the serial port, sent as a byte or series of bytes representing the digits of a number. As mentioned before, 0x00, 0 or NULL could be interpreted as a pointer, which causes this compilation error.

To solve this problem, you can force the function to read the provided value as a byte type by using a casting operator. For example, to pass 0x00 to the function:

 Serial.write((byte) 0x00);

It is always recommended to use the print() function instead, as explained in the Serial.write() function reference page.