more print format constants defined; function printNumber(..) adapted.

[TobiasKnauss]

I had already created a PR with the same content in arduino/ArduinoCore-avr#621, but I was told that the changes need to be accepted for the API first.

changes:

• added HEX2, HEX4, HEX8
• added BIN2, BIN4, BIN8, BIN16, BIN32
• adapted/enhanced Print::printNumber(unsigned long n, uint16_t base)

The number represents the minimum digit count for printing, i.e. adding leading zeros.

This enhancement was inspired by https://forum.arduino.cc/t/serial-print-value-hex/463868/5

It can be tested with the code example from https://docs.arduino.cc/language-reference/en/functions/communication/serial/print/ enhanced like this:

/*
  Uses a for loop to print numbers in various formats.
*/
void setup()
{
  Serial.begin(9600); // open the serial port at 9600 bps:
}

void loop()
{
  // print labels
  Serial.print("NO FORMAT"); // prints a label 
  Serial.print("\t"); // prints a tab
  Serial.print("DEC"); 
  Serial.print("\t");
  Serial.print("HEX"); 
  Serial.print("\t");
  Serial.print("HEX2"); 
  Serial.print("\t");
  Serial.print("HEX4"); 
  Serial.print("\t");
  Serial.print("HEX8"); 
  Serial.print("\t\t");
  Serial.print("OCT"); 
  Serial.print("\t");
  Serial.print("BIN");
  Serial.print("\t");
  Serial.print("BIN2");
  Serial.print("\t");
  Serial.print("BIN4");
  Serial.print("\t");
  Serial.print("BIN8");
  Serial.print("\t\t");
  Serial.print("BIN16");
  Serial.print("\t\t\t");
  Serial.print("BIN32");
  Serial.println(); // carriage return after the last label
  for (int x = 0; x < 64; x++)
  { // only part of the ASCII chart, change to suit
    // print it out in many formats:
    Serial.print(x); // print as an ASCII-encoded decimal - same as "DEC" 
    Serial.print("\t\t"); // prints two tabs to accomodate the label length
    Serial.print(x, DEC); // print as an ASCII-encoded decimal 
    Serial.print("\t"); // prints a tab
    Serial.print(x, HEX); // print as an ASCII-encoded hexadecimal 
    Serial.print("\t"); // prints a tab
    Serial.print(x, HEX2); // print as an ASCII-encoded hexadecimal 
    Serial.print("\t"); // prints a tab
    Serial.print(x, HEX4); // print as an ASCII-encoded hexadecimal 
    Serial.print("\t"); // prints a tab
    Serial.print(x, HEX8); // print as an ASCII-encoded hexadecimal 
    Serial.print("\t"); // prints a tab
    Serial.print(x, OCT); // print as an ASCII-encoded octal 
    Serial.print("\t"); // prints a tab
    Serial.print(x, BIN); // print as an ASCII-encoded binary 
    Serial.print("\t"); // prints a tab
    Serial.print(x, BIN2); // print as an ASCII-encoded binary 
    Serial.print("\t"); // prints a tab
    Serial.print(x, BIN4); // print as an ASCII-encoded binary 
    Serial.print("\t"); // prints a tab
    Serial.print(x, BIN8); // print as an ASCII-encoded binary 
    Serial.print("\t"); // prints a tab
    Serial.print(x, BIN16); // print as an ASCII-encoded binary 
    Serial.print("\t"); // prints a tab
    Serial.println(x, BIN32); // print as an ASCII-encoded binary 
    // then adds the carriage return with "println"
    delay(200); // delay 200 milliseconds
  }
  Serial.println(); // prints another carriage return
}

[TobiasKnauss]

Is this failed unit test related to my commit? If I understand it correctly, some external dependencies have failed and this test did not even run.

[TobiasKnauss]

Further improvements:

• Printing negative numbers in HEX always produced a 8-char-string, even if a byte (u/int8_t) or int (u/int16_t) was provided. The modifications now print in a length that matches the given variable type: byte -> 2-char HEX representation, int -> 4-char HEX representation, etc.

example output attached as file.
output.txt
Serial-print_1.ino.txt (remove ".txt" to run the test program).