Working version. NOW WITH UART DEBUG!

AVR/main.c

@@ -1,9 +1,34 @@
+#define F_CPU 8000000UL
+
 #include "../avr-i2c-slave/I2CSlave.h"
 #include <util/delay.h>
 #include <avr/io.h>
+
 #include <avr/interrupt.h>
 
-#define I2C_ADDR 0x30
+#define BAUDRATE 9600
+#define BAUD_PRESCALLER (((F_CPU / (BAUDRATE * 16UL))) - 1)
+
+#define I2C_ADDR 0x20
+
+void USART_init(void){
+  UBRR0H = (uint8_t)(BAUD_PRESCALLER>>8);
+  UBRR0L = (uint8_t)(BAUD_PRESCALLER);
+  UCSR0B = (1<<RXEN0)|(1<<TXEN0);
+  UCSR0C = (3<<UCSZ00);
+}
+
+void USART_send( unsigned char data){
+  while(!(UCSR0A & (1<<UDRE0)));
+  UDR0 = data;
+}
+ 
+void USART_putstring(char* StringPtr){
+  while(*StringPtr != 0x00){
+    USART_send(*StringPtr);
+    StringPtr++;
+  }
+}
 
 volatile uint8_t challenge = 0; // Use 0 as 'challenge not sent' condition
 uint16_t time_open = 0;
@@ -13,7 +38,13 @@ uint8_t check_challenge(uint8_t arg) {
 }
 
 void I2C_received(uint8_t received_data) {
-  if (received_data == check_challenge(challenge)) { // Check validity of response
+  uint8_t solution;
+  char message[100] = {0};
+
+  solution = check_challenge(challenge);
+  sprintf(message, "Response: %d. Expected: %d\n", received_data, solution);
+  USART_putstring(message);
+  if (received_data == solution) { // Check validity of response
     // Open lock
     time_open = 5000;
   }
@@ -22,6 +53,9 @@ void I2C_received(uint8_t received_data) {
 void I2C_requested() {
   challenge = (uint8_t)(TCNT1 & 0xff);
   I2C_transmitByte(challenge);
+  char message[100] = {0};
+  sprintf(message, "Request received. Sending %d\n", challenge);
+  USART_putstring(message);
 }
 
 void setup() {
@@ -36,8 +70,11 @@ void setup() {
 }
 
 int main() {
+  int i = 0;
   setup();
+  USART_init();
   while (1) {
+    i++;
     if (time_open > 0) {
       PORTC |= 2 << 1;
       time_open -= 1;
@@ -45,5 +82,10 @@ int main() {
       PORTC = 0;
     }
     _delay_ms(1);
+    if (i > 1000) {
+      char message[] = "Alive\n";
+      USART_putstring(message);
+      i = 0;
+    }
   }
 }

AVR/makefile

@@ -5,7 +5,7 @@
 # (GNU make, BSD make, SysV make)
 
 
-MCU = atmega88
+MCU = atmega328p
 FORMAT = ihex
 TARGET = main
 SRC = $(TARGET).c \