How can I define a port extender MCP23s17 pin in Arduino

Question

My task is to use a port extender (MCP23s17) to drive a touch keypad for which I have to define names of pins so that I can call those names in arguments of a function.

I have searched for different methods to define "PORT EXTENDER" pin but could not find any satisfactory results. Kindly help me handle the situation.

i have used the following libraries downloaded from Arduino playground 1. CapacitiveSensor.h 2. MCP23S17.h Now I have to use MCP23S17 Pin in the following function

#define key1 2
#define key2 4
CapacitiveSensor cs_4_2=Capacitivesensor(key2,key1);  //capacitive sensor is connected to pin 4 and 2

key1 and key2 are Arduino's pins. I want some method by which I can refer key1 and key2 to the port extender's (MSP23S17) pin. The above answers are surely helpful but they doesn't fulfill my requirement.

Thanks in Advance Sorry for English.

Answer 1

If you use this arduino library:

#define LED_PIN 15

mcp.pinMode(LED_PIN, LOW); //set led pin on the MCP23S17 to an OUTPUT

mcp.digitalWrite(LED_PIN, LOW)

Answer 2

If you are using my library you can do something like:

MCP23S17 expander1(&SPI, 10);

#define LED_PIN expander1, 15

void setPin(MCP23S17 &expander, int pin, bool level) {
    expander.digitalWrite(pin, level);
}

// ... later ...

setPin(LED_PIN, HIGH);

Answer 3

There is also the Adafruit Library, all do similar things, just in a slightly different way. I use this one, it just depends on which method you are most comfortable with and what your requirements are. Try them all and find out.

void setup() {
  Serial.begin(9600);  // debugging  
  mcp.begin();      // use default address 0

      for(int i = 0; i < 6; i++) {
        mcp.pinMode(trafficLights1[i], OUTPUT);
      }
       for(int i = 0; i < 6; i++) { 
        mcp.pinMode(trafficLights2[i], OUTPUT);
       }
        for(int i = 0; i < 5; i++) {
        mcp.pinMode(trafficLights3[i], OUTPUT);
        }
  for (int P=0;P<16;P++) {
    mcp.pullUp(P, HIGH);  // turn on a 100K pullup internally
    mcp.digitalWrite(P,LOW);
 }
      mcp.digitalWrite(11, HIGH);
}