Cleanup SPI_Multiple_Buses (#3527)

* Utilize prepoc symbols for SPI pins
* Adjusts for GPIO pins when ALTERNATE_PINS is set

libraries/SPI/examples/SPI_Multiple_Buses/SPI_Multiple_Buses.ino

@@ -15,6 +15,30 @@
  */
 #include <SPI.h>
 
+// Define ALTERNATE_PINS to use non-standard GPIO pins for SPI bus
+
+#ifdef ALTERNATE_PINS
+  #define VSPI_MISO   2
+  #define VSPI_MOSI   4
+  #define VSPI_SCLK   0
+  #define VSPI_SS     33
+
+  #define HSPI_MISO   26
+  #define HSPI_MOSI   27
+  #define HSPI_SCLK   25
+  #define HSPI_SS     32
+#else
+  #define VSPI_MISO   MISO
+  #define VSPI_MOSI   MOSI
+  #define VSPI_SCLK   SCK
+  #define VSPI_SS     SS
+
+  #define HSPI_MISO   12
+  #define HSPI_MOSI   13
+  #define HSPI_SCLK   14
+  #define HSPI_SS     15
+#endif
+
 static const int spiClk = 1000000; // 1 MHz
 
 //uninitalised pointers to SPI objects
@@ -28,22 +52,28 @@ void setup() {
   
   //clock miso mosi ss
 
+#ifndef ALTERNATE_PINS
   //initialise vspi with default pins
   //SCLK = 18, MISO = 19, MOSI = 23, SS = 5
   vspi->begin();
+#else
   //alternatively route through GPIO pins of your choice
-  //hspi->begin(0, 2, 4, 33); //SCLK, MISO, MOSI, SS
+  vspi->begin(VSPI_SCLK, VSPI_MISO, VSPI_MOSI, VSPI_SS); //SCLK, MISO, MOSI, SS
+#endif
 
+#ifndef ALTERNATE_PINS
   //initialise hspi with default pins
   //SCLK = 14, MISO = 12, MOSI = 13, SS = 15
   hspi->begin();
+#else
   //alternatively route through GPIO pins
-  //hspi->begin(25, 26, 27, 32); //SCLK, MISO, MOSI, SS
+  hspi->begin(HSPI_SCLK, HSPI_MISO, HSPI_MOSI, HSPI_SS); //SCLK, MISO, MOSI, SS
+#endif
 
   //set up slave select pins as outputs as the Arduino API
   //doesn't handle automatically pulling SS low
-  pinMode(5, OUTPUT); //VSPI SS
-  pinMode(15, OUTPUT); //HSPI SS
+  pinMode(VSPI_SS, OUTPUT); //VSPI SS
+  pinMode(HSPI_SS, OUTPUT); //HSPI SS
 
 }
 
@@ -60,9 +90,9 @@ void vspiCommand() {
 
   //use it as you would the regular arduino SPI API
   vspi->beginTransaction(SPISettings(spiClk, MSBFIRST, SPI_MODE0));
-  digitalWrite(5, LOW); //pull SS slow to prep other end for transfer
+  digitalWrite(VSPI_SS, LOW); //pull SS slow to prep other end for transfer
   vspi->transfer(data);  
-  digitalWrite(5, HIGH); //pull ss high to signify end of data transfer
+  digitalWrite(VSPI_SS, HIGH); //pull ss high to signify end of data transfer
   vspi->endTransaction();
 }
 
@@ -70,8 +100,8 @@ void hspiCommand() {
   byte stuff = 0b11001100;
   
   hspi->beginTransaction(SPISettings(spiClk, MSBFIRST, SPI_MODE0));
-  digitalWrite(15, LOW);
+  digitalWrite(HSPI_SS, LOW);
   hspi->transfer(stuff);
-  digitalWrite(15, HIGH);
+  digitalWrite(HSPI_SS, HIGH);
   hspi->endTransaction();
 }