From 4422daacf5b843dd36d7180d3c7fc5eca743bf3c Mon Sep 17 00:00:00 2001
From: Jon Langseth <jon.langseth@lilug.no>
Date: Wed, 8 Aug 2012 02:18:11 +0200
Subject: [PATCH 1/1] Storing some SPI example code

---
 master/master.ino | 65 +++++++++++++++++++++++++++++++++++++++++
 slave/slave.ino   | 74 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 139 insertions(+)
 create mode 100644 master/master.ino
 create mode 100644 slave/slave.ino

diff --git a/master/master.ino b/master/master.ino
new file mode 100644
index 0000000..8681436
--- /dev/null
+++ b/master/master.ino
@@ -0,0 +1,65 @@
+// Simple SPI MASTER example
+// Counts number of presses on a button connected to D2 (PD2),
+// and sends the count and the count+100 over SPI.
+// Uses a mix of Arduino and plain AVR code,
+// but does not use the Arduino SPI library.
+
+long int count=1; 
+
+void setup() 
+{ 
+  Serial.begin(115200); 
+  Serial.println("Hello from MASTER")
+  
+  // Declare pushbutton as input using the Arduino-way ;)
+  pinMode(2, INPUT);  
+  
+  // Set SCK, MOSI and SS as OUTPUTS using the AVR-way ;)
+  DDRB |= (1<<PB5)|(1<<PB3)|(1<<PB2);
+  // Enable SPI, MASTER mode, Fosc/64
+  SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR1); 
+
+  // Make sure SS is pulled HIGH
+  spi_ss_end(); 
+
+} 
+
+void loop() 
+{ 
+  // Loop with no action until button-pressed is
+  // detected
+  if (digitalRead(2)==HIGH) 
+  {
+    // Wait for button to go back to "idle"
+    while (digitalRead(2)==HIGH) {}
+    
+    count=count+1;     // Increment count
+    
+    Serial.print("Count: "); 
+    Serial.println(count, DEC);
+
+    spi_ss_start();    // Set /CS (SS) LOW for transmission
+    spi_rw(count);     // Send current count
+    spi_rw(count+100); // and a +100 version ;)
+    spi_ss_end();      // Re-set /CS (SS) HIGH after transmission 
+
+  } 
+} 
+
+// Using SS as outgoing /CS pin
+void spi_ss_start()
+{ 
+  PORTB &= ~(1<<PB2); // Set SS low using AVR logic ;)
+}
+void spi_ss_end()
+{
+  PORTB |= (1<<PB2);  // Set SS high using AVR logic ;)
+}
+
+uint8_t spi_rw( uint8_t d )
+{ 
+  SPDR = d;                    // Start the transmission 
+  while (!(SPSR & (1<<SPIF))); // Wait for transmission to complete
+  return SPDR;                 // Return the resulting register content
+}
+
diff --git a/slave/slave.ino b/slave/slave.ino
new file mode 100644
index 0000000..b7da468
--- /dev/null
+++ b/slave/slave.ino
@@ -0,0 +1,74 @@
+// Interrupt-driven SPI SLAVE example
+// Recieves bytes over SPI and stuffs them in
+// a sort-of-circular-buffer that is printed to Serial.
+// Uses a mix of Arduino and plain AVR code,
+// but does not use the Arduino SPI library.
+
+#include <avr/interrupt.h>
+
+volatile uint8_t buffer[16];
+volatile uint8_t bptr;
+
+
+void setup()
+{ 
+  Serial.begin(115200); 
+  Serial.println("Hello from SLAVE")
+
+    // A nice little debug/status pin, set as OUTPUT using the Arduino-way ;)
+    pinMode(7,  OUTPUT);
+
+  // Make sure our buffer-pointer starts at the first buffer byte (pos 0)
+  bptr = 0;
+
+  // Set MISO as OUTPUT using the AVR-way ;)
+  DDRB=(1<<DDB4);
+  // Enable SPI (default Slave) and enable SPI interrupts
+  SPCR=(1<<SPE)|(1<<SPIE); 
+
+  // Activate interrupts
+  sei();
+} 
+
+void loop()
+{
+  // In the main loop, simply output the buffer contents, over and over again..
+  Serial.print("b "); 
+  for ( uint8_t i = 0; i <= 15; i++ )
+  {
+    Serial.print(i);
+    Serial.print(" = "); 
+    Serial.print(buffer[i]); 
+    Serial.print("  ");  
+  }
+  Serial.println(" ... ");
+  delay(500);
+} 
+
+// The ISR for SPI Serial Transfer Complete gets triggered
+// on each byte transferred.
+ISR(SPI_STC_vect)
+{
+  // Put data in buffer, increment buffer pointer, wrap around on end.
+  buffer[bptr] = spi_read();
+  bptr++;
+  if (bptr > 15) bptr = 0;
+}
+
+uint8_t spi_read( ){ 
+  // Getting the transferred byte is as imple as reading the Data Register
+  // each time a byte has completed transfer. This and the ISR, needs to be
+  // quick, so that the next byte does not overwrite the current one.
+  
+  // Sending is done by setting the data register before reading ...
+  SPDR = 0;
+  uint8_t d = SPDR;
+  
+  // Let's add some fun "things happen because of transfers"...
+  if ( d == 45 ) digitalWrite(7, ( !digitalRead(7) ) );
+  
+  return d; 
+}
+
+
+
-- 
2.39.2