42_EXT_03_42chips/module02/ex04/main.c

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>		// https://www.nongnu.org/avr-libc/user-manual/group__avr__interrupts.html

#include "utils.h"
#include "bitmanip.h"
#include "timer.h"
#include "usart.h"
#include "interrupt.h"

// USART
#define USART_BAUDRATE		115200
// TIMER
#define PERIOD				2000
#define PRESCALE_VALUE		1024													// can be 1, 8, 64, 256, 1024
#define STRLEN_LITERAL(str)			(sizeof(str) / sizeof(str[0]) - 1)						// -1 to remove the null terminator, only works with string literals, not with pointers

// END MACROS

// FUNCTION PROTOTYPES
void uart_init();
// char uart_rx(void);
void uart_tx(char c);
void uart_printstr(const char* str);
void check_str(char input, volatile char compare_str[], unsigned int length);
void reset_message();
void ask_for_username();
void ask_for_password();
void on_error();
void on_success();

// GLOBAL VARIABLES
typedef enum {
    USERNAME,
    PASSWORD
} State;
volatile char username[] = "admin";
volatile char password[] = "password";
volatile int input_index = 0;
volatile State state = USERNAME;
volatile int input_match = FALSE;
volatile int username_correct = FALSE;
volatile int password_correct = FALSE;

void uart_init() {
	UBRR0H = (unsigned char) (BAUD_PRESCALER(USART_BAUDRATE) >> 8);					// 20.11.5 : UBRRnL and UBRRnH – USART Baud Rate Registers
	UBRR0L = (unsigned char) BAUD_PRESCALER(USART_BAUDRATE);

	UCSR0C |= ASYNCHRONOUS | PARITY_DISABLED | STOP_ONE_BIT | DATA_EIGHT_BIT;		// 20.11.4 : set Frame Format
	
	UCSR0B |= RECEIVER_ENABLED | TRANSMITTER_ENABLED | INTERRUPT_RECEIVER_ENABLED;	// 20.11.3 : enable Receiver and Transmitter, and interrupt on receiver
}

// char uart_rx(void) {
// 	while (TEST(UCSR0A, RXC0) == 0);												// 20.11.2 : do nothing until there are unread data in the receive buffer (UDRn), (RXCn flag in UCSRnA register set to 1 when buffer has data)
// 	return UDR0;																	// 20.11.1 : get data in buffer, UDRn – USART I/O Data Register (read and write)
// }

void uart_tx(char c) {
	while (TEST(UCSR0A, UDRE0) == 0);												// 20.11.2 : do nothing until UDRn buffer is empty, (UDREn flag in UCSRnA register set to 1 when buffer empty)
	UDR0 = (unsigned char) c;														// 20.11.1 : Put data into buffer, UDRn – USART I/O Data Register (read and write)
}

void uart_printstr(const char* str) {
	while (*str) {
		uart_tx(*str);
		str++;
	}
}

ISR(USART_RX_vect) {																// Table 12-7 : we select the code for USART Receive
	// char received_char = uart_rx();
	char received_char = UDR0;														// read received character
	if (received_char == '\b' || received_char == 127) {							// if backspace is received
		if (input_index <= 0) return;
		input_index--;
		uart_tx('\b');  // Move cursor back
		uart_tx(' ');   // Erase the character on screen
		uart_tx('\b');  // Move cursor back again
	} else if (received_char == '\n' || received_char == '\r') {					// if enter is received
		if (state == USERNAME) {
			if (input_index == STRLEN_LITERAL(username) && input_match) {
				username_correct = TRUE;
			} else {
				username_correct = FALSE;
				uart_printstr("(error1)");
			}
			input_match = FALSE;
			state = PASSWORD;
			input_index = 0;
			uart_tx('\r');															// Move cursor to next line
			uart_tx('\n');
			ask_for_password();
		} else if (state == PASSWORD) {
			if (!username_correct) {
				uart_printstr("(error2)");
				return reset_message();
			}
			if (input_index != STRLEN_LITERAL(password)) {
				uart_printstr("(error3)");
				return reset_message();
			}
			if (!input_match) {
				uart_printstr("(error4)");
				return reset_message();
			}
			uart_tx('\r');															// Move cursor to next line
			uart_tx('\n');
			on_success();
		}
	} else {
		if (state == USERNAME) {
			check_str(received_char, username, STRLEN_LITERAL(username));
			uart_tx(received_char);
		}
		else if (state == PASSWORD) {
			check_str(received_char, password, STRLEN_LITERAL(password));
			uart_tx('*');
		}
		input_index++;
	}
}

void check_str(char input, volatile char compare_str[], unsigned int length) {
	if (input_index >= length) {														// index has not already been incremented, so we need to compare greater or equal
		uart_printstr("(error5)");
		input_match = FALSE;
		return;
	}
	if (input != compare_str[input_index]) {
		uart_printstr("(error6)");
		input_match = FALSE;
		return;
	}
	// if we reach this point, the input character matches the compare_str character
	if (input_index == 0) {
		input_match = TRUE;
		return;
	}
	// if we reach this point, the input character is not the first character of the compare_str
	if (input_match == FALSE) {
		// if any previous character did not match, we don't need to check the next character
		uart_printstr("(error7)");
		return;
	}
	input_match = TRUE;
}

void reset_message() {
	input_index = 0;
	input_match = FALSE;
	username_correct = FALSE;
	password_correct = FALSE;
	state = USERNAME;
	uart_tx('\r');																// Move cursor to next line
	uart_tx('\n');
	on_error();
	ask_for_username();
}
void ask_for_username() {
	uart_printstr("Enter your login: \r\n    username: ");
}
void ask_for_password() {
	uart_printstr("    password: ");
}
void on_error() {
	uart_printstr("Bad combinaison username/password\r\n\r\n");
}
void on_success() {
	uart_printstr("Hello spectre!\r\nShall we play a game?\r\n");
}

// ask for username and password
// `screen /dev/ttyUSB0 115200`
int main() {
	uart_init();
	ask_for_username();

	SREG |= ENABLE_GLOBAL_INTERRUPT;												// 7.3.1 : Status Register, bit 7 : I – Global Interrupt Enable

	while(1);
}