From 1a1287f089b21d1218ce17ad71f2ec7484ef6e3f Mon Sep 17 00:00:00 2001
From: Davide Bongiovanni <Davide Bongiovanni>
Date: Wed, 18 Jan 2017 23:32:22 +0100
Subject: [PATCH] Modified master architecture. Adjusted behavior to the new
 slave device architecture. The program quits as soon as it's done talking to
 the slave.

---
 RPi/i2c_challenge.c | 61 +++++++++++++++++++--------------------------
 1 file changed, 25 insertions(+), 36 deletions(-)

diff --git a/RPi/i2c_challenge.c b/RPi/i2c_challenge.c
index cd4a114..094f272 100644
--- a/RPi/i2c_challenge.c
+++ b/RPi/i2c_challenge.c
@@ -21,41 +21,30 @@
 #include <wiringPi.h>
 #include <wiringPiI2C.h>
 
-int main (int argc, char *argv[])
-{
-        int fd;
-        int data;
-	int send=1;
-        wiringPiSetup () ;
-        fd=wiringPiI2CSetup (0x20) ;  /*Use i2cdetect command to find your respective device address*/
-        if(fd==-1)
-        {
-                printf("Can't setup the I2C device\n");
-                return -1;
-        }
-        else
-        {
-		delay(1);
-		while(1) {
-		wiringPiI2CWrite(fd, send);
-                        data=wiringPiI2CRead(fd);
-                        printf(" Received data=%d\n", data);
-                        if(data==-1)
-                        {
-                                printf("No data\n");
-                                //return -1;
-                        }
-			else if(data == 17) {
-				printf("Exit code received \n");
-				break;
-			}
-                        else if(data != 0) {
-				printf("Sending response %d\n", data+3 );
-				wiringPiI2CWrite(fd, data+3);
-                        } 
-			
-                }
-        }
-        return 0;
+#define I2C_ADDR 0x20
+
+uint8_t solve_challenge(uint8_t arg) {
+  return (arg >> 3) ^ (arg << 3);
 }
 
+int main(int argc, char *argv[]) {
+
+  int fd; // Linux filehandle to the i2c device
+  uint8_t challenge;
+  uint8_t response;
+  wiringPiSetup();
+
+  fd = wiringPiI2CSetup(I2C_ADDR); // Initialize the i2c protocol with the address
+  if (fd == -1) { // Failed to contact device
+    printf("Can't setup the I2C device\n");
+    return -1;
+  }
+
+  delay(1);
+
+  challenge = wiringPiI2CRead(fd);
+  response = solve_challenge(challenge);
+  wiringPiI2CWrite(response);
+
+  return 0;
+}