/**
   * @brief Set the pin mode to  input, output or pull-up input (internal 100KΩ pull-up resistor)
   * @param pin Pin number, it could be all enumeration values (eGPA0-eGPB7/ 0-15) included in ePin_t.
   * @param mode Mode, it can be set to Input, Output, Pull-up Input (internal 100KΩ pull-up resistor)
   * @return Return 0 if the setting is successful, otherwise return non-zero. 
   */
  int pinMode(ePin_t pin, uint8_t mode);

  /**
   * @brief Write digtial pin. The pin needs to be set to output mode before writing.
   * @param pin Pin number, it could be all enumeration values (eGPA0-eGPB7/ 0-15) inlcuded in ePin_t.
   * @param level High level 1 or Low level 0
   * @return Return 0 if the writing is successful, otherwise return non-zero. 
   */
  int digitalWrite(ePin_t pin, uint8_t level);

  /**
   * @brief Read digital pin. The pin needs to be set to input mode before reading. 
   * @param pin Pin number, it could be all enumeration values (eGPA0-eGPB7/ 0-15) included in ePin_t.
   * @return Return High or Low
   */
  int digitalRead(ePin_t pin);

  /**
   * @brief Set a pin to interrupt mode
   * @param pin Pin number, it could be all enumeration values (eGPA0-eGPB7/ 0-15) included in ePin_t.
   * @param mode Interrupt mode: all enumeration values included in eInterruptMode_t.
   * @param cb Interrupt service function, needs to be defined and transferred parameter by users. Prototype: void func(int)
   */
  void pinModeInterrupt(ePin_t pin, eInterruptMode_t mode,  MCP23017_INT_CB cb);

  /**
   * @brief Poll if an interrupt occurs on a port group.
   * @param group Port group, it could be all enumeration values included in eGPIOGroup_t,  GPIO GroupA(eGPIOA), 
   * @n GPIO GroupB(eGPIOB) GroupA+B (eGPIOALL).
   * @n When setting to eGPIOA，poll if an interrupt occurs on the port group A. 
   * @n When setting to eGPIOB, poll if an interrupt occurs on the port group B.
   * @n When setting to eGPIOALL, poll if an interrupt occurs on the port group A+B
   * @n None, poll if an interrupt occurs on the all ports of group A and B by default. 
   */
  void pollInterrupts(eGPIOGroup_t group=eGPIOALL);

  /**
   * @brief Convert pin into string description
   * @param pin Pin number, it could be all enumeration values (eGPA0-eGPB7/ 0-15) inlcuded in ePin_t.
   * @return Return pin description string
   * @n such as "eGPA0" "eGPA1" "eGPA2" "eGPA3" "eGPA4" "eGPA5" "eGPA6" "eGPA7"
   * @n   "eGPB0" "eGPB1" "eGPB2" "eGPB3" "eGPB4" "eGPB5" "eGPB6" "eGPB7"
   * @n   "eGPA" "eGPB"
   */
  String pinDescription(ePin_t pin);

  /**
   * @brief Convert pin into string description 
   * @param pin  Pin number, range 0~15
   * @return Return pin description string
   * @n such as "eGPA0" "eGPA1" "eGPA2" "eGPA3" "eGPA4" "eGPA5" "eGPA6" "eGPA7"
   * @n   "eGPB0" "eGPB1" "eGPB2" "eGPB3" "eGPB4" "eGPB5" "eGPB6" "eGPB7"
   * @n   "eGPA" "eGPB"
   */
  String pinDescription(int pin);