AVR SPI Code Added

SPI of AVR/SPI_Master.c

@@ -0,0 +1,92 @@
+// Post: "The SPI of the AVR" - SPI Master Code
+// URL: http://maxembedded.com/2013/11/26/the-spi-of-the-avr/
+// Authors: Yash Tambi, VIT University, India
+//          Mayank (Max) Prasad, Arizona State University, USA
+//          support@maxEmbedded.com
+
+/* 	DISCLAIMER
+
+	This is the same code as given in the above URL. Though the code is tested and approved, the author
+	is not responsible for any damage, physical, mental or social, which might occur due to the implementation
+	of this code and its derivatives, whether in full or part thereof. Use it at your own risk.
+
+	LICENSE
+	
+	The user is free to modify, reuse, reproduce and distribute the code and its derivatives to any extent,
+	whether for free or paid. The user can also use this code for commercial purposes. In other words,
+	do whatever you want with the code!
+   
+*/
+
+
+/*
+ * SPI_Master.c
+ *
+ * Created: 12/13/2013 2:19:02 AM
+ *  Author: Yash Tambi
+ */ 
+
+#ifndef F_CPU
+#define F_CPU 16000000UL
+#endif
+
+#include <avr/io.h>
+#include <util/delay.h>
+#include <avr/interrupt.h>
+
+#define ACK 0x7E
+#define LONG_TIME 10000
+
+//Initialize SPI Master Device
+void spi_init_master (void)            
+{
+    DDRB = (1<<5)|(1<<3);              //Set MOSI, SCK as Output
+    SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0); //Enable SPI, Set as Master
+                                       //Prescaler: Fosc/16, Enable Interrupts
+}
+
+//Function to send and receive data
+unsigned char spi_tranceiver (unsigned char data)
+{
+    SPDR = data;                       //Load data into the buffer
+    while(!(SPSR)&(1<<SPIF));          //Wait until transmission complete
+    return(SPDR);                      //Return received data
+}
+
+//Function to blink LED
+void led_blink (uint8_t i)
+{
+    //Blink LED "i" number of times
+    for (; i>0; --i)
+    {
+        PORTD|=(1<<0);
+        _delay_ms(100);
+        PORTD=(0<<0);
+        _delay_ms(100);
+    }
+}
+
+//Main
+int main(void)
+{
+    spi_init_master();                  //Initialize SPI Master
+    DDRD |= 0x01;                       //PD0 as Output
+
+    unsigned char data;                 //Received data stored here
+    uint8_t x = 0;                      //Counter value which is sent
+
+    while(1)
+    {
+        data = 0x00;                    //Reset ACK in "data"
+        data = spi_tranceiver(++x);     //Send "x", receive ACK in "data"
+        if(data == ACK) {               //Check condition
+            //If received data is the same as ACK, blink LED "x" number of times
+            led_blink(x);
+        }
+        else {
+            //If received data is not ACK, then blink LED for a long time so as to determine error
+            led_blink(LONG_TIME);
+        }
+        _delay_ms(500);                 //Wait 
+    }
+}

SPI of AVR/SPI_Slave.c

@@ -0,0 +1,75 @@
+// Post: "The SPI of the AVR" - SPI Slave Code
+// URL: http://maxembedded.com/2013/11/26/the-spi-of-the-avr/
+// Authors: Yash Tambi, VIT University, India
+//          Mayank (Max) Prasad, Arizona State University, USA
+//          support@maxEmbedded.com
+
+/* 	DISCLAIMER
+
+	This is the same code as given in the above URL. Though the code is tested and approved, the author
+	is not responsible for any damage, physical, mental or social, which might occur due to the implementation
+	of this code and its derivatives, whether in full or part thereof. Use it at your own risk.
+
+	LICENSE
+	
+	The user is free to modify, reuse, reproduce and distribute the code and its derivatives to any extent,
+	whether for free or paid. The user can also use this code for commercial purposes. In other words,
+	do whatever you want with the code!
+   
+*/
+
+
+/*
+ * SPI_Slave.c
+ *
+ * Created: 12/13/2013 2:20:06 AM
+ *  Author: Yash Tambi
+ */ 
+
+#ifndef F_CPU
+#define F_CPU 16000000UL
+#endif
+
+#include <avr/io.h>
+#include <stdlib.h>
+#include <util/delay.h>
+#include "lcd.h"
+
+#define ACK 0x7E
+
+void spi_init_slave (void)
+{
+    DDRB=(1<<6);                                  //MISO as OUTPUT
+    SPCR=(1<<SPE);                                //Enable SPI
+}
+
+//Function to send and receive data
+unsigned char spi_tranceiver (unsigned char data)
+{
+    SPDR = data;                                  //Load data into buffer
+    while(!(SPSR)&(1<<SPIF));                     //Wait until transmission complete
+    return(SPDR);                                 //Return received data
+}
+
+int main(void)
+{
+    lcd_init(LCD_DISP_ON_CURSOR_BLINK);           //Initialize LCD
+    spi_init_slave();                             //Initialize slave SPI
+
+    unsigned char data, buffer[10];
+
+    DDRA  = 0x00;                                 //Initialize PORTA as INPUT
+    PORTA = 0xFF;                                 //Enable Pull-Up Resistors
+
+    while(1)
+    {
+        lcd_clrscr();                             //LCD Clear screen
+        lcd_home();                               //LCD move cursor to home 
+        lcd_puts("Testing");
+        lcd_gotoxy(0,1);
+        data = spi_tranceiver(ACK);               //Receive data, send ACK
+        itoa(data, buffer, 10);                   //Convert integer into string
+        lcd_puts(buffer);                         //Display received data
+        _delay_ms(20);                            //Wait
+    }
+}