Merge pull request #89 from caternuson/intcap

Add INTCAP support

Author: caternuson

examples/mcp23xxx_interrupt/mcp23xxx_interrupt.ino

@@ -55,6 +55,12 @@ void loop() {
   if (!digitalRead(INT_PIN)) {
     Serial.print("Interrupt detected on pin: ");
     Serial.println(mcp.getLastInterruptPin());
-    delay(250); // debounce
+    Serial.print("Pin states at time of interrupt: 0b");
+    Serial.println(mcp.getCapturedInterrupt(), 2);
+    delay(250);  // debounce
+    // NOTE: If using DEFVAL, INT clears only if interrupt
+    // condition does not exist.
+    // See Fig 1-7 in datasheet.
+    mcp.clearInterrupts();  // clear
   }
 }

src/Adafruit_MCP23XXX.cpp

@@ -207,12 +207,25 @@ void Adafruit_MCP23XXX::disableInterruptPin(uint8_t pin) {
 
 /**************************************************************************/
 /*!
-  @brief Gets the last interrupt pin.
-  @returns Pin that caused last interrupt.
+  @brief Clear interrupts. NOTE:If using DEFVAL, INT clears only if interrupt
+  condition does not exist. See Fig 1-7 in datasheet.
+*/
+/**************************************************************************/
+void Adafruit_MCP23XXX::clearInterrupts() {
+  // reading INTCAP register(s) clears interrupts
+  // just call this and ignore return
+  getCapturedInterrupt();
+}
+
+/**************************************************************************/
+/*!
+  @brief Gets the pin that caused the latest interrupt, from INTF, without
+  clearing any interrupt flags.
+  @returns Pin that caused lastest interrupt.
 */
 /**************************************************************************/
 uint8_t Adafruit_MCP23XXX::getLastInterruptPin() {
-  uint8_t intpin = 255;
+  uint8_t intpin = MCP23XXX_INT_ERR;
   uint8_t intf;
 
   // Port A
@@ -227,7 +240,7 @@ uint8_t Adafruit_MCP23XXX::getLastInterruptPin() {
   }
 
   // Port B and still not found?
-  if ((pinCount > 8) && (intpin == 255)) {
+  if ((pinCount > 8) && (intpin == MCP23XXX_INT_ERR)) {
     Adafruit_BusIO_Register INTFB(i2c_dev, spi_dev, MCP23XXX_SPIREG,
                                   getRegister(MCP23XXX_INTF, 1));
     INTFB.read(&intf);
@@ -239,15 +252,34 @@ uint8_t Adafruit_MCP23XXX::getLastInterruptPin() {
     }
   }
 
-  // clear if found
-  if (intpin != 255) {
-    Adafruit_BusIO_Register INTCAP(
-        i2c_dev, spi_dev, MCP23XXX_SPIREG,
-        getRegister(MCP23XXX_INTCAP, MCP_PORT(intpin)));
-    INTCAP.read();
+  return intpin;
+}
+
+/**************************************************************************/
+/*!
+  @brief Get pin states captured at time of interrupt.
+  @returns Mutli-bit value representing pin states.
+*/
+/**************************************************************************/
+uint16_t Adafruit_MCP23XXX::getCapturedInterrupt() {
+  uint16_t intcap;
+  uint8_t intf;
+
+  // Port A
+  Adafruit_BusIO_Register INTCAPA(i2c_dev, spi_dev, MCP23XXX_SPIREG,
+                                  getRegister(MCP23XXX_INTCAP, 0));
+  INTCAPA.read(&intf);
+  intcap = intf;
+
+  // Port B ?
+  if (pinCount > 8) {
+    Adafruit_BusIO_Register INTCAPB(i2c_dev, spi_dev, MCP23XXX_SPIREG,
+                                    getRegister(MCP23XXX_INTCAP, 1));
+    INTCAPB.read(&intf);
+    intcap |= (uint16_t)intf << 8;
   }
 
-  return intpin;
+  return intcap;
 }
 
 /**************************************************************************/

src/Adafruit_MCP23XXX.h

@@ -30,6 +30,8 @@
 
 #define MCP_PORT(pin) ((pin < 8) ? 0 : 1) //!< Determine port from pin number
 
+#define MCP23XXX_INT_ERR 255 //!< Interrupt error
+
 /**************************************************************************/
 /*!
     @brief  Base class for all MCP23XXX variants.
@@ -57,7 +59,9 @@ class Adafruit_MCP23XXX {
   void setupInterrupts(bool mirroring, bool openDrain, uint8_t polarity);
   void setupInterruptPin(uint8_t pin, uint8_t mode = CHANGE);
   void disableInterruptPin(uint8_t pin);
+  void clearInterrupts();
   uint8_t getLastInterruptPin();
+  uint16_t getCapturedInterrupt();
 
 protected:
   Adafruit_I2CDevice *i2c_dev = NULL; ///< Pointer to I2C bus interface