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48 lines
1.1 KiB
48 lines
1.1 KiB
#include "../avr-i2c-slave/I2CSlave.h"
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#include <util/delay.h>
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#define I2C_ADDR 0x20
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volatile uint8_t challenge = 0; // Use 0 as 'challenge not sent' condition
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uint8_t check_challenge(uint8_t arg) {
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return (arg >> 3) ^ (arg << 3);
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}
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void I2C_received(uint8_t received_data) {
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if (challenge != 0) {
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if (check_challenge(received_data) == check_challenge(challenge)) { // Check validity of response
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// Open lock
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PORTC |= 2 << 1;
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_delay_ms(5000);
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PORTC = 0;
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}
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}
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challenge = 0;
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}
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void I2C_requested() {
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challenge = (uint8_t)(TCNT1 & 0xff); // Use content of timer as pseudo-random number
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if (challenge == 0) // Prevent 'challenge' from being 0, which has a special meaning
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challenge = 1;
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I2C_transmitByte(challenge);
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}
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void setup() {
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// set received/requested callbacks
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I2C_setCallbacks(I2C_received, I2C_requested);
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// init I2C
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I2C_init(I2C_ADDR);
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// init output gpio
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DDRC = 0b00000100; // PC2
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TCNT1 = 0;
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TCCR1B |= (1 << CS10) | (1 << CS11); // No prescaling
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}
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int main() {
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setup();
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while (1); // All the work is done in the callbacks
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}
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