make it work

src/as1115.c

@@ -0,0 +1,7 @@
+#include "as1115.h"
+#include "i2c.h"
+
+int as1115_send_command(uint8_t cmd, uint8_t data) {
+	uint8_t packet[] = {cmd, data};
+	return i2c_write(0x00, packet, sizeof packet);
+}

src/as1115.h

@@ -0,0 +1,23 @@
+#include <stdint.h>
+
+#define DIGIT_0_REG 0x01
+#define DIGIT_1_REG 0x02
+#define DIGIT_2_REG 0x03
+#define DIGIT_3_REG 0x04
+#define DIGIT_4_REG 0x05
+#define DIGIT_5_REG 0x06
+#define DIGIT_6_REG 0x07
+#define DIGIT_7_REG 0x08
+#define DECODE_MODE_REG 0x09
+#define GLOBAL_INTENSITY_REG 0x0A
+#define SCAN_LIMIT_REG 0x0B
+#define SHUTDOWN_REG 0x0C
+#define SELF_ADDRESSING_REG 0x0D
+#define FEATURE_REG 0x0E
+#define DISPLAY_TEST_MODE_REG 0x0F
+#define DIG_0_1_INTENSITY_REG 0x10
+#define DIG_2_3_INTENSITY_REG 0x11
+#define DIG_4_5_INTENSITY_REG 0x12
+#define DIG_6_7_INTENSITY_REG 0x13
+
+int as1115_send_command(uint8_t cmd, uint8_t data);

src/config.h

@@ -0,0 +1,5 @@
+#include <stdint.h>
+
+#define OSCILLATOR_CALIBRATION 0x76
+#define STARTING_TIME_MS (uint32_t)10*60*1000 // 10 min
+// #define STARTING_TIME_MS (uint32_t)5*1000 // 5 sec

src/i2c.c

@@ -0,0 +1,78 @@
+#include <stdbool.h>
+#include <stdint.h>
+
+#include <avr/io.h>
+#include <avr/interrupt.h>
+
+#include "i2c.h"
+
+void i2c_init() {
+	DDRA |= _BV(SDA_BIT) | _BV(SCL_BIT); // Set SDA and SCL to output
+	PORTA |= _BV(SDA_BIT) | _BV(SCL_BIT); // Write HIGH to SDA and SCL
+}
+
+#define HIGH 1
+#define LOW 0
+
+void port_a_put(uint8_t pin, bool value) {
+	if(value) {
+		PORTA |= _BV(pin);
+		DDRA &= ~_BV(pin);
+	} else {
+		PORTA &= ~_BV(pin);
+		DDRA |= _BV(pin);
+	}
+}
+
+int i2c_write_byte(uint8_t byte) {
+	for (int i = 7; i >= 0; i--) {
+		port_a_put(SDA_BIT, (byte & 0x80) != 0);
+		byte <<= 1;
+
+		// pulse clock
+		port_a_put(SCL_BIT, HIGH);
+		port_a_put(SCL_BIT, LOW);
+	}
+
+	port_a_put(SDA_BIT, HIGH);
+
+	// check ACK
+
+	port_a_put(SCL_BIT, HIGH);
+
+	int ack = PINA & _BV(SDA_BIT);
+
+	port_a_put(SCL_BIT, LOW);
+
+	return ack;
+}
+
+int i2c_write(uint8_t addr, const uint8_t* data, uint8_t len) {
+	// START condition
+	port_a_put(SDA_BIT, LOW);
+
+	port_a_put(SCL_BIT, LOW);
+
+	// write address
+	int ack = i2c_write_byte(addr);
+	if (ack) {
+		port_a_put(SDA_BIT, HIGH);
+		port_a_put(SCL_BIT, HIGH);
+		return 1;
+	}
+
+	for (int i = 0; i < len; i++) {
+		int ack = i2c_write_byte(data[i]);
+		if (ack) {
+			port_a_put(SDA_BIT, HIGH);
+			port_a_put(SCL_BIT, HIGH);
+			return 1;
+		}
+	}
+
+	// STOP condition
+	port_a_put(SCL_BIT, HIGH);
+	port_a_put(SDA_BIT, HIGH);
+
+	return 0;
+}

src/i2c.h

@@ -0,0 +1,4 @@
+#include <stdint.h>
+
+void i2c_init();
+int i2c_write(uint8_t addr, const uint8_t* data, uint8_t len);

src/main.c

@@ -0,0 +1,130 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+#include <avr/io.h>
+#include <avr/interrupt.h>
+
+#include "config.h"
+#include "as1115.h"
+#include "i2c.h"
+
+#define PLAYER_A_BUTTON 0
+#define PLAYER_B_BUTTON 1
+
+volatile uint32_t ms_since_boot = 0;
+
+typedef enum {
+	STOPPED,
+	PLAYER_A,
+	PLAYER_B
+} state_type;
+
+volatile state_type state = STOPPED;
+
+volatile uint32_t player_a_timer = STARTING_TIME_MS;
+volatile uint32_t player_b_timer = STARTING_TIME_MS;
+
+ISR(TIM1_COMPA_vect)
+{
+	ms_since_boot++;
+
+	if(state == PLAYER_A) {
+		player_a_timer--;
+		if(player_a_timer == 0) { state = STOPPED; }
+	} else if(state == PLAYER_B) {
+		player_b_timer--;
+		if(player_b_timer == 0) { state = STOPPED; }
+	}
+}
+
+void setupio(void) {
+	// Set port A to inputs
+	DDRA = 0x00;
+	PORTA |= _BV(PORTA0) | _BV(PORTA1); // pull-up
+
+	// Set port B to output
+	DDRB = 0xFF;
+}
+
+void setup_clock(void) {
+	OSCCAL = OSCILLATOR_CALIBRATION;
+
+	TCCR1B = 0x09;
+	OCR1A = 1000;
+	TIMSK1 = 0x02;
+}
+
+bool button_pressed(uint8_t pin) {
+	return (PINA & (1 << pin)) == 0;
+}
+
+#define DISPLAY_LEFT 0
+#define DISPLAY_RIGHT 1
+
+void render_timer(unsigned long ms, uint8_t display) {
+	uint8_t digits[4] = {0xFF, 0xFF, 0xFF, 0xFF};
+
+	if (ms == 0) {
+		memset(&digits, 0x0A, 4); // show all dashes
+		goto render;
+	}
+
+	uint8_t sec = (ms + (1000 - 1)) / 1000 % 60;
+	uint8_t min = (ms + (1000 - 1)) / 1000 / 60;
+
+	digits[3] = sec % 10;
+	digits[2] = sec / 10;
+
+	if (min != 0) {
+		digits[1] = min % 10;
+		if (min >= 10) {
+			digits[0] = min / 10;
+		}
+	}
+
+render:
+	switch(display) {
+		case DISPLAY_LEFT:
+			as1115_send_command(0x01, digits[0]);
+		    as1115_send_command(0x02, digits[1]);
+		    as1115_send_command(0x03, digits[2]);
+		    as1115_send_command(0x04, digits[3]);
+			break;
+		case DISPLAY_RIGHT:
+			as1115_send_command(0x05, digits[0]);
+		    as1115_send_command(0x06, digits[1]);
+		    as1115_send_command(0x07, digits[2]);
+		    as1115_send_command(0x08, digits[3]);
+			break;
+	}
+}
+
+int main() {
+	cli();
+	setupio();
+	i2c_init();
+	setup_clock();
+	sei();
+
+	render_timer(STARTING_TIME_MS, DISPLAY_LEFT);
+	render_timer(STARTING_TIME_MS, DISPLAY_RIGHT);
+
+	as1115_send_command(SHUTDOWN_REG, 0x01); // turn on
+    as1115_send_command(DECODE_MODE_REG, 0xFF); // decode
+    as1115_send_command(SCAN_LIMIT_REG, 0x07); // enable all digits
+
+	while(true) {
+		render_timer(player_a_timer, DISPLAY_LEFT);
+		render_timer(player_b_timer, DISPLAY_RIGHT);
+
+		cli();
+		if(button_pressed(PLAYER_A_BUTTON) && player_b_timer != 0 && player_a_timer != 0) {
+			state = PLAYER_B;
+		}
+
+		if(button_pressed(PLAYER_B_BUTTON) && player_b_timer != 0 && player_a_timer != 0) {
+			state = PLAYER_A;
+		}
+		sei();
+	}
+}