coffee/barista/barista.ino

/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
 * SPDX-License-Identifier: GPL-3.0-or-later */

#include "ntc.h"
#include "pinout.h"
#include <avr/wdt.h>

enum logic {
	ON = 1,
	OFF = 0,
};

#define DEBOUNCE_TIME 20L /* ms */
#define TEMP_MIN 40.0f /* C */
#define TEMP_MAX 50.0f /* C */

#define LED_MIN_VALUE 0

enum machine_state {
	SLEEPING = 0,
	DEBOUNCE,
	HEATING,
	HOT,
	BREWING,
	COOLING,
};

//int state = SLEEPING;

enum btn_index {
	BTN_ON = 0,
	BTN_HOT,
	MAX_BTN,
};

enum btn_state {
	RESTING = 0,
	PRESSING,
	PRESSED,
	RELEASING,
	RELEASED,
};

enum buzz_state {
	BUZZ_OFF = 0,
	BUZZ_HEY,
	BUZZ_ACTIVE,
};


int button_pin[MAX_BTN] = {
	[BTN_ON] = PIN_POWER_ON,
	[BTN_HOT] = PIN_HOT,
};

struct btn {
	enum btn_state state;
	unsigned long press_t0;
	unsigned long release_t0;
};

struct input {
	unsigned long t_ms;
	int ntc_V;
	enum logic btn[MAX_BTN];
} g_in;

#define MAX_SAMPLES 16

struct state {
	enum machine_state mstate;
	unsigned long brewing_t0;
	unsigned long cooling_t0;
	unsigned long heating_t0;
	unsigned long hot_t0;

	int ntc_i; /* Next available place */
	float ntc_R;
	float ntc_last_T;
	float ntc_array_T[MAX_SAMPLES];
	float ntc_T; /* average */

	struct btn btn[MAX_BTN];
	enum buzz_state buzz_state;
	unsigned long buzz_t0;
} g_st;

int read_input(int pin)
{
	return !digitalRead(pin);
}

void relay(int pin, enum logic st)
{
	/* Relays are active low */
	if (st == ON)
		digitalWrite(pin, 0);
	else
		digitalWrite(pin, 1);
}

void setled(int pin, enum logic st)
{
	/* LEDs are active high */
	if (st == ON)
		digitalWrite(pin, 1);
	else
		digitalWrite(pin, 0);
}

void do_input(struct input *input)
{
	input->t_ms = millis();

	/* Read buttons */
	for (int i = 0; i < MAX_BTN; i++)
		input->btn[i] = read_input(button_pin[i]);

	/* Read temperature sensor */
	input->ntc_V = analogRead(PIN_NTC);
}

void proc_ntc(struct state *state, const struct input *input)
{
	state->ntc_R = ntc_resistance(input->ntc_V);
	state->ntc_last_T = ntc_temp(state->ntc_R);
	state->ntc_array_T[state->ntc_i++] = state->ntc_last_T;
	if (state->ntc_i >= MAX_SAMPLES)
		state->ntc_i = 0;

	float avg = 0;
	for (int i = 0; i < MAX_SAMPLES; i++)
		avg += state->ntc_array_T[i];

	state->ntc_T = avg / MAX_SAMPLES;
}

void proc_buttons(struct state *state, const struct input *input)
{
	for (int i = 0; i < MAX_BTN; i++) {
		struct btn *btn = &state->btn[i];
		int v = input->btn[i];

		if (btn->state == RESTING) {
			if (v == ON) {
				btn->state = PRESSING;
				btn->press_t0 = millis();
			}
		} else if (btn->state == PRESSING) {
			if (v != ON) {
				btn->state = RESTING;
			} else if (millis() - btn->press_t0 > DEBOUNCE_TIME) {
				btn->state = PRESSED;
			}
		} else if (btn->state == PRESSED) {
			if (v != ON) {
				btn->state = RELEASING;
				btn->release_t0 = millis();
			}
		} else if (btn->state == RELEASING) {
			if (v == ON) {
				btn->state = PRESSED;
			} else if (millis() - btn->release_t0 > DEBOUNCE_TIME) {
				btn->state = RELEASED;
			}
		} else if (btn->state == RELEASED) {
			btn->state = RESTING;
		}
	}
}

int red_min = 50;
int red_state = red_min;
unsigned long brewing_time     = 3000UL; /* 3 seconds */
unsigned long cooling_time     = 3000UL; /* 3 seconds */
unsigned long max_heating_time = 60000UL; /* 60 seconds */
unsigned long max_idle_time    = 10000UL; /* 10 seconds */

void proc_machine(struct state *st)
{
	float temp = st->ntc_T;
	int on = (st->btn[BTN_ON].state == RELEASED);
	int hot = (st->btn[BTN_HOT].state == PRESSED);

	Serial.print("t=");
	Serial.print(millis());
	Serial.print(" state=");
	Serial.print(st->mstate);
	Serial.print(" on=");
	Serial.print(on);
	Serial.print(" temp=");
	Serial.print(temp);
	Serial.println(" C");

	/* Pressing ON cancels any operation */
	if (st->mstate != SLEEPING && on) {
		st->mstate = SLEEPING;
		st->buzz_state = BUZZ_OFF;
		return;
	}

	if (st->mstate == SLEEPING) {
		if (on) {
			st->mstate = HEATING;
			st->heating_t0 = millis();
			Serial.println("heating");
		}
	} else if (st->mstate == HEATING) {
		if (temp > TEMP_MAX) {
			st->mstate = HOT;
			st->hot_t0 = millis();
			st->buzz_state = BUZZ_HEY;
			Serial.println("hot");
		} else if (millis() - st->heating_t0 > max_heating_time) {
			/* TODO: Add alarm state */
			st->mstate = SLEEPING;
			Serial.println("cannot heat, going to sleep");
		}
	} else if (st->mstate == HOT) {
		if (hot) {
			st->mstate = BREWING;
			st->brewing_t0 = millis();
			Serial.println("brewing");
		} else if (millis() - st->hot_t0 > max_idle_time) {
			st->mstate = SLEEPING;
			Serial.println("idle timeout, going to sleep");
		}
	} else if (st->mstate == BREWING) {
		if (millis() - st->brewing_t0 > brewing_time) {
			st->mstate = COOLING;
			st->cooling_t0 = millis();
			Serial.println("cooling");
		}
	} else if (st->mstate == COOLING) {
		/* TODO: Wait a bit and go back to heating */
		if (millis() - st->cooling_t0 > cooling_time) {
			st->mstate = HEATING;
			st->heating_t0 = millis();
			Serial.println("heating");
		}
	}
}

void
proc_buzz(struct state *st)
{
	if (st->buzz_state == BUZZ_HEY) {
		tone(PIN_BUZZ, 1500);
		st->buzz_state = BUZZ_ACTIVE;
		st->buzz_t0 = millis();
	} else if (st->buzz_state == BUZZ_ACTIVE) {
		if (millis() - st->buzz_t0 > 20) {
			st->buzz_state = BUZZ_OFF;
			noTone(PIN_BUZZ);
		}
	} else {
		noTone(PIN_BUZZ);
	}
}

void do_proc(struct state *st, const struct input *input)
{
	proc_ntc(st, input);
	proc_buttons(st, input);
	proc_machine(st);
	proc_buzz(st);
}

void
output_leds(const struct state *st)
{
	static int r = 0;
	static int g = 0;

	if (st->mstate == HEATING || st->mstate == COOLING) {
		analogWrite(PIN_LED_RED, r);
		setled(PIN_LED_GREEN, 0);
		if (r >= 255)
			r = 0;
		else
			r += 3;
	} else if (st->mstate == HOT) {
		setled(PIN_LED_RED, 0);
		setled(PIN_LED_GREEN, 1);
		r = 0;
	} else if (st->mstate == BREWING) {
		setled(PIN_LED_RED, 0);
		analogWrite(PIN_LED_GREEN, g);
		if (g >= 255)
			g = 0;
		else
			g += 3;
	} else {
		setled(PIN_LED_RED, 0);
		setled(PIN_LED_GREEN, 0);
		r = 0;
	}
}

void
output_heater(const struct state *st)
{
	if (st->mstate == HEATING || st->mstate == HOT || st->mstate == BREWING) {
		if (st->ntc_T < TEMP_MIN)
			relay(PIN_HEAT, ON);
		else if (st->ntc_T > TEMP_MAX)
			relay(PIN_HEAT, OFF);
	} else {
		relay(PIN_HEAT, OFF);
	}
}

void
output_pump(const struct state *st)
{
	if (st->mstate == BREWING)
		relay(PIN_PUMP, ON);
	else
		relay(PIN_PUMP, OFF);
}

void do_output(const struct state *st)
{
	output_leds(st);
	output_heater(st);
}

void setup()
{
	wdt_disable();
	Serial.begin(9600);
	Serial.println("Booting");

	pinMode(PIN_POWER_ON, INPUT);
	pinMode(PIN_HOT, INPUT);

	pinMode(PIN_LED_RED, OUTPUT);
	pinMode(PIN_LED_GREEN, OUTPUT);
	pinMode(PIN_HEAT, OUTPUT);
	pinMode(PIN_PUMP, OUTPUT);

	/* Turn all relays off */
	relay(PIN_HEAT, OFF);
	relay(PIN_PUMP, OFF);

	Serial.println("Ready");
	wdt_enable(WDTO_250MS);
}

void loop()
{
	do_input(&g_in);
	do_proc(&g_st, &g_in);
	do_output(&g_st);

	delay(5);
	wdt_reset();
}