packet layout beautified

ArduinoConfig.h

@@ -1,9 +1,30 @@
 #ifndef ARDUINOCONFIG_H_
 #define ARDUINOCONFIG_H_
 
+static const uint8_t COMMAND_TRANSFER_SPI = 1;
+
 #define BAUD_RATE               115200
 #define SERIAL_RX_BUFFER_SIZE   256
 #define RING_BUFFER_SIZE        100
 #define MAX_PACKET_LENGTH       100
 
+// Define which port to use for the SPI Chip Select by using the register
+// definitions. The data direction register is assigned as well.
+// The ports can be looked up on the official Arduino pinout schematics.
+#ifdef ARDUINO_AVR_MEGA2560
+// Defines for the Arduino Mega
+#define CS_PORT PORTK
+#define CS_DDR DDRK
+#elif defined(ARDUINO_AVR_UNO)
+#define CS_PORT PORTD
+#define CS_DDR DDRD
+#elif defined(__SAM3X8E__)
+// Define for the Arduino Due
+#define CS_PORT PORTC
+#define CS_DDR DDRC
+#else
+#define CS_PORT PORTC
+#define CS_DDR DDRC
+#endif
+
 #endif /* ARDUINOCONFIG_H_ */