Arduino Leonardo and DFRobot MCP23017 expansion board

Afternoon all - I have been playing with making a controller using various toggle and rotary switches - it became apparent that there were not going to be enough pins on the Arduino Leonardo board that I have. So I purchased an expansion board - DFRobot MCP23017.

Not having used one before I loaded the example button sketch onto the Leonardo so I could figure out how it works. It seemd fairly straight forward - so I then started to incorporate the code into the existing joystick sketch I had been working on. Initially everything seemed to be working fine, but when I came back the next day to carry on I had all sorts of issues. I had thought that perhaps a wire had come lose, but having checked all the wires that isn't the case.

If I load the sketch removing all instances that refer to the MCP board , the 3 toggle switches I have assigned on the Leonardo work perfectly - each toggle is on-off-on, or on-off-mom - so 6 pins in all assigned on the Leonardo. 1-6 

I have a seperate on-off-on toggle as an experiement on the MCP board. If I load the sketch below but DO NOT attach any of the 3 toggle switches to the Leonardo, the switch on the MCP works fine.  The toggle swiches are 3 pin with the ground/ common the middle pin. the two outer pins are connected to the IO pins on PB0 and PB1 respectively.

If however I attach a toggle switch to pins1 and 2 on the Leaornado, after a few seconds of operation the board locks up so I have to reboot the card. The same thing happens if I use the exact same switch on pins 3 and 4........however…… if I attach the exact same switch to pins 5 and 6 it works perfectly in unison with the toggle switch attached to the MCP card!

So in short for some reason I can't use pins 1-4 on the Leonardo with the MCP configured.

I am at a loss - it seems like there is some sort of addressing issue going on but I don't have that indepth kind of knowledge - hoping someone here does - please see sketch below:

#include <Joystick.h>

#include <DFRobot_MCP23017.h>

DFRobot_MCP23017 mcp(Wire, 0x20);

#define Collective A0

int rxAxis_ = 0;

#define Throttle A1

int Throttle_ = 0;

#define Button1 PD1

#define Button2 PD2

#define Button3 PD3

#define Button4 PD4

#define Button5 PD5

#define Button6 PD6

#define Button7 mcp.eGPB0

#define Button8 mcp.eGPB1

int lastButton1State = 0;

int lastButton2State = 0;

int lastButton3State = 0;

int lastButton4State = 0;

int lastButton5State = 0;

int lastButton6State = 0;

int lastButton7State = 0;

int lastButton8State = 0;

Joystick_ Joystick(0x08, JOYSTICK_TYPE_JOYSTICK,

                   9, 0,  // Button Count, Hat Switch Count

                   false, false, false,  // X and Y, Z Axis

                   true, false, false,  //  Rx, Ry, or Rz

                   false, true,  //  rudder, throttle

                   false, false, false);  // accelerator, brake, or steering

const bool initAutoSendState = true;

void setup() {

  Joystick.begin();

  mcp.begin();

  pinMode(Button1, INPUT_PULLUP);

  pinMode(Button2, INPUT_PULLUP);

  pinMode(Button3, INPUT_PULLUP);

  pinMode(Button4, INPUT_PULLUP);

  pinMode(Button5, INPUT_PULLUP);

  pinMode(Button6, INPUT_PULLUP);

  mcp.pinMode(mcp.eGPB0, INPUT_PULLUP);

  mcp.pinMode(mcp.eGPB1, INPUT_PULLUP);

  Serial.begin(9600);

}

void loop() {

  Throttle_ = analogRead(Throttle) / 04;

  Throttle_ = map(Throttle_, 0, 1023, 0, 255);

  Joystick.setThrottle(Throttle_);

  rxAxis_ = analogRead(Collective);

  rxAxis_ = map(rxAxis_, 0, 1023, 0, 255);

  Joystick.setRxAxis(rxAxis_);

  int currentButton1State = !digitalRead(Button1);

  if (currentButton1State != lastButton1State) {

    Joystick.setButton(0, currentButton1State);

    lastButton1State = currentButton1State;

  }

  int currentButton2State = !digitalRead(Button2);

  if (currentButton2State != lastButton2State) {

    Joystick.setButton(1, currentButton2State);

    lastButton2State = currentButton2State;

  }

  int currentButton3State = !digitalRead(Button3);

  if (currentButton3State != lastButton3State) {

    Joystick.setButton(2, currentButton3State);

    lastButton3State = currentButton3State;

  }

  int currentButton4State = !digitalRead(Button4);

  if (currentButton4State != lastButton4State) {

    Joystick.setButton(3, currentButton4State);

    lastButton4State = currentButton4State;

  }

  int currentButton5State = !digitalRead(Button5);

  if (currentButton5State != lastButton5State) {

    Joystick.setButton(4, currentButton5State);

    lastButton5State = currentButton5State;

  }

  int currentButton6State = !digitalRead(Button6);

  if (currentButton6State != lastButton6State) {

    Joystick.setButton(5, currentButton6State);

    lastButton6State = currentButton6State;

  }

  int currentButton7State = !mcp.digitalRead(Button7);

  if (currentButton7State != lastButton7State) {

    Joystick.setButton(6, currentButton7State);

    lastButton7State = currentButton7State;

  }

  int currentButton8State = !mcp.digitalRead(Button8);

  if (currentButton8State != lastButton8State) {

    Joystick.setButton(7, currentButton8State);

    lastButton8State = currentButton8State;

  }

  Joystick.sendState();

  delay(100);

}