cc253x: Configurable linkage for the P2 ISR

See Pull Request #18

cpu/cc253x/dev/p2-intr.h

@@ -45,7 +45,11 @@ void cc253x_p2_register_handler(struct cc253x_p2_handler *h);
 
 void cc253x_p2_unregister_handler(struct cc253x_p2_handler *h);
 
+/* When the ISR is not needed, hide its prototype from the module containing
+ * main() to prevent linking it */
+#if PORT_2_ISR_ENABLED
 void cc253x_p2_int(void) __interrupt(P2INT_VECTOR);
+#endif
 
 #define cc253x_p2_irq_disable(flag) do { flag = IEN2 & 0x2; IEN2 &= ~0x2; } while(0)
 #define cc253x_p2_irq_enable(flag) do { IEN2 |= flag; } while(0)

platform/cc2530dk/contiki-conf.h

@@ -98,6 +98,14 @@
 #define CC2530_CONF_MAC_FROM_PRIMARY 1
 #endif
 
+/* Interrupt Number 6: Shared between P2 Inputs, I2C and USB
+ * A single ISR handles all of the above. Leave this as is if you are not
+ * interested in any of the above. Define as 1 (e.g. in project-conf.h) if
+ * at least one of those interrupt sources will need handled */
+#ifndef PORT_2_ISR_ENABLED
+#define PORT_2_ISR_ENABLED 0
+#endif
+
 /*
  * Sensors
  * It is harmless to #define XYZ 1

platform/cc2530dk/models.h

@@ -67,6 +67,9 @@
 #if MODEL_CC2531
 #define USB_CONF_ENABLE 1
 
+/* Enabled the ISR for Interrupt Num 6 */
+#define PORT_2_ISR_ENABLED 1
+
 #ifndef USB_CONF_CLASS
 #define DMA_CONF_ON	1
 #define DMA_USB_CHANNEL	0