Add thermostat and heater control

barista/barista.ino

@@ -4,6 +4,8 @@
 #include "ntc.h"
 #include "overheat.h"
 #include "led.h"
+#include "heater.h"
+#include "thermostat.h"
 #include "pinout.h"
 #include <avr/wdt.h>
 
@@ -13,8 +15,7 @@ enum logic {
 };
 
 #define DEBOUNCE_TIME 20L /* ms */
-#define TEMP_MIN 40.0f /* C */
+#define TEMP_HOT 70.0f /* C */
-#define TEMP_MAX 50.0f /* C */
 
 #define LED_MIN_VALUE 0
 
@@ -51,7 +52,6 @@ enum buzz_state {
 	BUZZ_ACTIVE,
 };
 
-
 int button_pin[MAX_BTN] = {
 	[BTN_ON] = PIN_POWER_ON,
 	[BTN_HOT] = PIN_HOT,
@@ -94,6 +94,9 @@ struct state {
 
 	struct led red_led;
 	struct led green_led;
+
+	struct heater heater;
+	struct thermostat thermostat;
 } g_st;
 
 int read_input(int pin)
@@ -191,27 +194,29 @@ void proc_buttons(struct state *state, const struct input *input)
 
 int red_min = 50;
 int red_state = red_min;
-unsigned long brewing_max_time =  3000UL; /* 3 seconds */
+unsigned long brewing_max_time =  30000UL; /*  30 seconds */
 unsigned long cooling_time     =   3000UL; /*   3 seconds */
 unsigned long overheat_time    =  10000UL; /*  10 seconds */
 unsigned long max_heating_time =  60000UL; /*  60 seconds */
-unsigned long max_idle_time    = 10000UL; /* 10 seconds */
+unsigned long max_idle_time    = 120000UL; /* 120 seconds */
 
 void proc_machine(struct state *st)
 {
+	static unsigned long last_print_t = 0;
+
 	float temp = st->ntc_T;
 	int on = (st->btn[BTN_ON].state == RELEASED);
 	int brew_hot = (st->btn[BTN_HOT].state == PRESSED);
+	unsigned long t = millis();
 
-	Serial.print("t=");
+	if (t - last_print_t > 100) {
-	Serial.print(millis());
+		Serial.print(t);
-	Serial.print(" state=");
+		Serial.print(" ");
 		Serial.print(st->mstate);
-	Serial.print(" on=");
+		Serial.print(" ");
-	Serial.print(on);
+		Serial.println(temp);
-	Serial.print(" temp=");
+		last_print_t = t;
-	Serial.print(temp);
+	}
-	Serial.println(" C");
 
 	/* If the machine is overheating */
 	if (overheat_panic(&st->overheat)) {
@@ -239,7 +244,7 @@ void proc_machine(struct state *st)
 			Serial.println("heating");
 		}
 	} else if (st->mstate == HEATING) {
-		if (temp > TEMP_MIN) {
+		if (temp > TEMP_HOT) {
 			st->mstate = HOT;
 			st->hot_t0 = millis();
 			st->buzz_state = BUZZ_HEY;
@@ -349,14 +354,25 @@ output_leds(const struct state *st)
 void
 output_heater(const struct state *st)
 {
-	if (st->mstate == HEATING || st->mstate == HOT || st->mstate == BREWING_HOT) {
+	unsigned long t = millis();
-		if (st->ntc_T < TEMP_MIN)
+
+	/* First configure thermostate */
+	if (st->mstate == HEATING || st->mstate == HOT || st->mstate == BREWING_HOT)
+		thermostat_set(&st->thermostat, TEMP_HOT);
+	else
+		thermostat_off(&st->thermostat);
+
+	/* Then update heater state from thermostate */
+	if (thermostat_state(&st->thermostat, st->ntc_T))
+		heater_on(&st->heater, t);
+	else
+		heater_off(&st->heater);
+
+	/* Then switch relays accordingly */
+	if (heater_state(&st->heater, t))
 		relay(PIN_HEAT, ON);
-		else if (st->ntc_T > TEMP_MAX)
+	else
 		relay(PIN_HEAT, OFF);
-	} else {
-		relay(PIN_HEAT, OFF);
-	}
 }
 
 void

barista/heater.c

@@ -0,0 +1,47 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include "heater.h"
+
+#define HEATER_T_ON	500UL /* ms */
+#define HEATER_T_OFF	5000UL /* ms */
+
+void
+heater_on(struct heater *h, unsigned long t_ms)
+{
+	if (h->st == HEATER_ON)
+		return;
+
+	h->next_t = t_ms + HEATER_T_ON;
+	h->st = HEATER_ON;
+	h->turn_on = 1;
+}
+
+void
+heater_off(struct heater *h)
+{
+	h->st = HEATER_OFF;
+	h->turn_on = 0;
+}
+
+int
+heater_state(struct heater *h, unsigned long t_ms)
+{
+	if (h->st == HEATER_OFF)
+		return 0;
+
+	/* Switch state if current time exceeds time limit
+	 * in the current state */
+	/* FIXME: Integer overflow can cause the heater to turn on forever */
+	if (t_ms > h->next_t) {
+		if (h->turn_on) {
+			h->turn_on = 0;
+			h->next_t = t_ms + HEATER_T_OFF; 
+		} else {
+			h->turn_on = 1;
+			h->next_t = t_ms + HEATER_T_ON; 
+		}
+	}
+
+	return h->turn_on;
+}

barista/heater.h

@@ -0,0 +1,30 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#ifndef BARISTA_HEATER_H
+#define BARISTA_HEATER_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+enum heater_state {
+	HEATER_OFF = 0,
+	HEATER_ON,
+};
+
+struct heater {
+	enum heater_state st;
+	int turn_on;
+	unsigned long next_t; /* in ms */
+};
+
+void heater_on(struct heater *h, unsigned long t_ms);
+void heater_off(struct heater *h);
+int heater_state(struct heater *h, unsigned long t_ms);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BARISTA_HEATER_H */

barista/thermostat.c

@@ -0,0 +1,41 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include "thermostat.h"
+
+#define DELTA_LOW	1.0
+#define DELTA_HIGH	1.0
+
+void
+thermostat_set(struct thermostat *th, float temp_target)
+{
+	if (th->st == THERMOSTAT_ON && th->temp_target == temp_target)
+		return;
+
+	th->st = THERMOSTAT_ON;
+	th->temp_target = temp_target;
+	th->temp_min = temp_target - DELTA_LOW;
+	th->temp_max = temp_target + DELTA_HIGH;
+	th->on = 1;
+}
+
+void
+thermostat_off(struct thermostat *th)
+{
+	th->st = THERMOSTAT_OFF;
+	th->on = 0;
+}
+
+int
+thermostat_state(struct thermostat *th, float temp)
+{
+	if (th->st == THERMOSTAT_OFF)
+		return 0;
+
+	if (th->on && temp > th->temp_max)
+		th->on = 0;
+	else if (!th->on && temp < th->temp_min)
+		th->on = 1;
+
+	return th->on;
+}

barista/thermostat.h

@@ -0,0 +1,32 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#ifndef BARISTA_THERMOSTAT_H
+#define BARISTA_THERMOSTAT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+enum thermostat_state {
+	THERMOSTAT_OFF = 0,
+	THERMOSTAT_ON,
+};
+
+struct thermostat {
+	enum thermostat_state st;
+	float temp_target;
+	float temp_min;
+	float temp_max;
+	int on;
+};
+
+void thermostat_set(struct thermostat *th, float temp_target);
+void thermostat_off(struct thermostat *th);
+int thermostat_state(struct thermostat *th, float temp);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BARISTA_THERMOSTAT_H */