code: func (t *TM1638Driver) fromStringToByteArray(str string) []byte {
  	chars := strings.Split(str, "")
  	data := make([]byte, len(chars))
  
  	for index, char := range chars {
  		if val, ok := t.fonts[char]; ok {
  			data[index] = val
  		}
  	}
  	return data
  }
docs: // fromStringToByteArray translates a string to a byte array with the corresponding representation for the 7-segment LCD, return and empty character if the font is not available