Almost working version

RPi/i2c_challenge.c

@@ -23,7 +23,7 @@
 #include <wiringPiI2C.h>
 
 uint8_t solve_challenge(uint8_t arg) {
-  return (arg >> 3) ^ (arg << 3);
+  return (arg >> 3);
 }
 
 uint8_t parse_int(const char *s) { // Convert string to hex
@@ -67,8 +67,11 @@ int main(int argc, char *argv[]) {
   delay(1);
 
   challenge = wiringPiI2CRead(fd);
+  printf("Received %d\n", challenge);
   response = solve_challenge(challenge);
-  wiringPiI2CWrite(fd, response);
+  printf("Sending %d\n", response);
+  delay(100);
+  wiringPiI2CWrite(fd, (uint8_t)response);
 
   return 0;
 }