Implement PID thremostat controller

For now only the proportional (Kp) and derivative (Kd) components are
used, the integral term is 0.

barista/.gitignore

@@ -1 +1,4 @@
 build/
+misc/
+*.test
+*.o

barista/Makefile

@@ -1,17 +1,49 @@
+# Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+# SPDX-License-Identifier: GPL-3.0-or-later
+
 PORT=/dev/ttyUSB0
 FQBN=arduino:avr:atmega328bb
-OPTS=--no-color --log-level=info -v
+OPTS=--no-color --log-level=info
+#OPTS+=-v
 PROJ=barista
 BUILD=build/$(subst :,.,$(FQBN))
 HEX=$(BUILD)/$(PROJ).ino.hex
 
+SRC=barista.ino \
+    ntc.c \
+    ntc.h \
+    pinout.h \
+    overheat.c \
+    overheat.h
+
+TESTS=ntc.test \
+      overheat.test \
+      led.test
+
+# For host test programs
+CPPFLAGS=-I.
+LIBS=-lm
+
 all: $(HEX)
 
-$(HEX): barista.ino
+$(HEX): $(SRC)
 	arduino-cli compile $(OPTS) -e --fqbn $(FQBN)
 
 upload: $(HEX)
 	avrdude -vv -p atmega328p -c arduino -P $(PORT) -b 9600 -D -U flash:w:$(HEX):i
 
 serial:
-	picocom -b 115200 --lower-rts --lower-dtr /dev/ttyUSB0 --imap lfcrlf
+	picocom -b 9600 --lower-rts --lower-dtr /dev/ttyUSB0 --imap lfcrlf
+
+test: ntc.test overheat.test led.test
+
+%.test: test/test_%.o test/compat.o %.o
+	gcc $^ -o $@ $(LIBS)
+
+thermostat.test: test/test_thermostat.o test/compat.o thermostat.o overheat.o heater.o
+	gcc $^ -o $@ $(LIBS)
+
+clean:
+	rm -f $(TESTS) test/*.o *.o
+
+.PHONY: test all clean

barista/barista.ino

@@ -1,64 +1,13 @@
 /* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
  * SPDX-License-Identifier: GPL-3.0-or-later */
 
-/*
- *                             ATmega328p
- *                            +---------+
- *  (PCINT14/RESET)      PC6 -|1  \_/ 28|- PC5 (ADC5/SCL/PCINT13)
- *  (PCINT16/RXD)        PD0 -|2      27|- PC4 (ADC4/SDA/PCINT12)
- *  (PCINT17/TXD)        PD1 -|3      26|- PC3 (ADC3/PCINT11)
- *  (PCINT18/INT0)       PD2 -|4      25|- PC2 (ADC2/PCINT10)
- *  (PCINT19/OC2B/INT1)  PD3 -|5      24|- PC1 (ADC1/PCINT9)
- *  (PCINT20/XCK/T0)     PD4 -|6      23|- PC0 (ADC0/PCINT8)
- *  VCC                      -|7      22|-     GND
- *  GND                      -|8      21|-     AREF
- *  (PCINT6/XTAL1/TOSC1) PB6 -|9      20|-     AVCC
- *  (PCINT7/XTAL2/TOSC2) PB7 -|10     19|- PB5 (SCK/PCINT5)
- *  (PCINT21/OC0B/T1)    PD5 -|11     18|- PB4 (MISO/PCINT4)
- *  (PCINT22/OC0A/AIN0)  PD6 -|12     17|- PB3 (MOSI/OC2A/PCINT3)
- *  (PCINT23/AIN1)       PD7 -|13     16|- PB2 (SS/OC1B/PCINT2)
- *  (PCINT0/CLKO/ICP1)   PB0 -|14     15|- PB1 (OC1A/PCINT1)
- *                            +---------+
- *
- * 
- *         ATMEL ATMEGA8 & 168 / ARDUINO
- *
- *                          +-\/-+
- *                    PC6  1|    |28  PC5 (AI 5)
- *              (D 0) PD0  2|    |27  PC4 (AI 4)
- *              (D 1) PD1  3|    |26  PC3 (AI 3)
- *              (D 2) PD2  4|    |25  PC2 (AI 2)
- *         PWM+ (D 3) PD3  5|    |24  PC1 (AI 1)
- *              (D 4) PD4  6|    |23  PC0 (AI 0)
- *                    VCC  7|    |22  GND
- *                    GND  8|    |21  AREF
- *                    PB6  9|    |20  AVCC
- *                    PB7 10|    |19  PB5 (D 13)
- *         PWM+ (D 5) PD5 11|    |18  PB4 (D 12)
- *         PWM+ (D 6) PD6 12|    |17  PB3 (D 11) PWM
- *              (D 7) PD7 13|    |16  PB2 (D 10) PWM
- *              (D 8) PB0 14|    |15  PB1 (D 9) PWM
- *                          +----+
- *
- *
- */
-
-enum pinout {
-	/* Inputs */
-	PIN_POWER_ON  = 8,
-	PIN_HOT       = 9,
-	//PIN_FLOW      = PIN_D5,
-
-	/* Outputs */
-	PIN_LED_GREEN = 5,
-	PIN_LED_RED   = 6,
-	PIN_HEAT      = 7,
-	PIN_PUMP      = 12,
-	PIN_BUZZ      = 10,
-
-	/* Analog */
-	PIN_NTC       = PIN_A0,
-};
+#include "ntc.h"
+#include "overheat.h"
+#include "led.h"
+#include "heater.h"
+#include "thermostat.h"
+#include "pinout.h"
+#include <avr/wdt.h>
 
 enum logic {
 	ON = 1,
@@ -66,30 +15,30 @@ enum logic {
 };
 
 #define DEBOUNCE_TIME 20L /* ms */
-#define TEMP_MIN 600
-#define TEMP_MAX 700
+#define TEMP_HOT 75.0f /* C */
 
 #define LED_MIN_VALUE 0
 
-enum state {
-	SLEEPING,
+enum machine_state {
+	SLEEPING = 0,
 	DEBOUNCE,
 	HEATING,
 	HOT,
-	BREWING,
+	BREWING_HOT,
+	BREWING_COLD,
 	COOLING,
+	PANIC_OVERHEAT,
 };
 
-long debounce_t0 = 0;
-int state = SLEEPING;
+//int state = SLEEPING;
 
-enum button {
-	BUTTON_ON = 0,
-	BUTTON_HOT,
-	MAX_BUTTON,
+enum btn_index {
+	BTN_ON = 0,
+	BTN_HOT,
+	MAX_BTN,
 };
 
-enum button_state {
+enum btn_state {
 	RESTING = 0,
 	PRESSING,
 	PRESSED,
@@ -98,21 +47,57 @@ enum button_state {
 };
 
 enum buzz_state {
-  BUZZ_OFF = 0,
-  BUZZ_HEY,
-  BUZZ_STOP,
+	BUZZ_OFF = 0,
+	BUZZ_HEY,
+	BUZZ_ACTIVE,
 };
 
-int buzz_state;
-
-int button_pin[MAX_BUTTON] = {
-	[BUTTON_ON] = PIN_POWER_ON,
-	[BUTTON_HOT] = PIN_HOT,
+int button_pin[MAX_BTN] = {
+	[BTN_ON] = PIN_POWER_ON,
+	[BTN_HOT] = PIN_HOT,
 };
 
-int button_state[MAX_BUTTON];
-unsigned long button_press_t0[MAX_BUTTON];
-unsigned long button_release_t0[MAX_BUTTON];
+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 */
+	int ntc_n; /* Samples in array */
+	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;
+
+	struct overheat overheat;
+	unsigned long overheat_t0;
+
+	struct led red_led;
+	struct led green_led;
+
+	struct heater heater;
+	struct thermostat thermostat;
+} g_st;
 
 int read_input(int pin)
 {
@@ -121,205 +106,297 @@ int read_input(int pin)
 
 void relay(int pin, enum logic st)
 {
-  /* Relays are active low */
-  if (st == ON)
-    digitalWrite(pin, 0);
-  else
-    digitalWrite(pin, 1);
+	/* 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);
+	/* LEDs are active high */
+	if (st == ON)
+		digitalWrite(pin, 1);
+	else
+		digitalWrite(pin, 0);
 }
 
-void update_buttons()
+void do_input(struct input *input)
 {
-	for (int i = 0; i < MAX_BUTTON; i++) {
-		int st = button_state[i];
-		int pin = button_pin[i];
-		if (st == RESTING) {
-			if (read_input(pin) == ON) {
-				button_state[i] = PRESSING;
-				button_press_t0[i] = millis();
+	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;
+	if (state->ntc_n < MAX_SAMPLES)
+		state->ntc_n++;
+
+	float avg = 0;
+	for (int i = 0; i < state->ntc_n; i++)
+		avg += state->ntc_array_T[i];
+
+	state->ntc_T = avg / state->ntc_n;
+
+	overheat_input(&state->overheat, millis(), state->ntc_T);
+}
+
+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 (st == PRESSING) {
-			if (read_input(pin) != ON) {
-				button_state[i] = RESTING;
-			} else if (millis() - button_press_t0[i] > DEBOUNCE_TIME) {
-				button_state[i] = PRESSED;
+		} else if (btn->state == PRESSING) {
+			if (v != ON) {
+				btn->state = RESTING;
+			} else if (millis() - btn->press_t0 > DEBOUNCE_TIME) {
+				btn->state = PRESSED;
 			}
-		} else if (st == PRESSED) {
-			if (read_input(pin) != ON) {
-				button_state[i] = RELEASING;
-				button_release_t0[i] = millis();
+		} else if (btn->state == PRESSED) {
+			if (v != ON) {
+				btn->state = RELEASING;
+				btn->release_t0 = millis();
 			}
-		} else if (st == RELEASING) {
-			if (read_input(pin) == ON) {
-				button_state[i] = PRESSED;
-			} else if (millis() - button_release_t0[i] > DEBOUNCE_TIME) {
-				button_state[i] = RELEASED;
+		} else if (btn->state == RELEASING) {
+			if (v == ON) {
+				btn->state = PRESSED;
+			} else if (millis() - btn->release_t0 > DEBOUNCE_TIME) {
+				btn->state = RELEASED;
 			}
-		} else if (st == RELEASED) {
-			button_state[i] = RESTING;
+		} else if (btn->state == RELEASED) {
+			btn->state = RESTING;
 		}
 	}
 }
 
+/* In PANIC_OVERHEAT state wait at least TIME_OVERHEAT_COOL and until the
+ * temperature goes below TIME_OVERHEAT_TEMP before doing anything. */
+#define TIME_OVERHEAT_COOL  10000 /* ms */
+#define TIME_OVERHEAT_TEMP  40.0  /* °C */
+
 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 = 10000UL; /* 10 seconds */
-unsigned long max_idle_time    = 10000UL; /* 10 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    = 300000UL; /* 300 seconds */
 
-void progress()
+void proc_machine(struct state *st)
 {
-	int temp = analogRead(PIN_NTC);
-	int on = (button_state[BUTTON_ON] == RELEASED);
-	int hot = (button_state[BUTTON_HOT] == PRESSED);
+	static unsigned long last_print_t = 0;
 
-  static unsigned long brewing_t0 = 0;
-  static unsigned long cooling_t0 = 0;
-  static unsigned long heating_t0 = 0;
-  static unsigned long hot_t0 = 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("state=");
-	Serial.print(state);
-	Serial.print(" on=");
-	Serial.print(on);
-	Serial.print(" temp=");
-	Serial.println(temp);
+	/* If the machine is overheating */
+	if (overheat_panic(&st->overheat)) {
+		st->mstate = PANIC_OVERHEAT;
+		st->overheat_t0 = millis();
+		Serial.println("PANIC OVERHEATING");
+	}
 
-  /* Pressing ON cancels any operation */
-	if (state != SLEEPING && on) {
-			state = SLEEPING;
-      return;
-  }
+	/* Pressing ON cancels any operation */
+	if (st->mstate != SLEEPING && on) {
+		st->mstate = SLEEPING;
+		st->buzz_state = BUZZ_OFF;
+		return;
+	}
 
-	if (state == SLEEPING) {
-		if (on) {
-			state = HEATING;
-      heating_t0 = millis();
+	if (st->mstate == SLEEPING) {
+		/* Allow brewing cold at without turning the heater */
+		/* FIXME: Use the cold button instead */
+		if (brew_hot) {
+			st->mstate = BREWING_COLD;
+			Serial.println("brewing cold");
+		} else if (on) {
+			st->mstate = HEATING;
+			st->heating_t0 = millis();
 			Serial.println("heating");
 		}
-	} else if (state == HEATING) {
-    if (temp > TEMP_MAX) {
-      state = HOT;
-      hot_t0 = millis();
-      buzz_state = BUZZ_HEY;
-      Serial.println("hot");
-    } else if (millis() - heating_t0 > max_heating_time) {
-      /* TODO: Add alarm state */
-      state = SLEEPING;
-      Serial.println("cannot heat, going to sleep");
-    }
-	} else if (state == HOT) {
-		if (hot) {
-			state = BREWING;
-      brewing_t0 = millis();
-      Serial.println("brewing");
-    } else if (millis() - hot_t0 > max_idle_time) {
-      state = SLEEPING;
-      Serial.println("idle timeout, going to sleep");
-    }
-	} else if (state == BREWING) {
-    if (millis() - brewing_t0 > brewing_time) {
-      state = COOLING;
-      cooling_t0 = millis();
-      Serial.println("cooling");
-    }
-  } else if (state == COOLING) {
-    /* TODO: Wait a bit and go back to heating */
-    if (millis() - cooling_t0 > cooling_time) {
-      state = HEATING;
-      heating_t0 = millis();
-      Serial.println("heating");
-    }
-  }
+	} else if (st->mstate == HEATING) {
+		if (temp > TEMP_HOT) {
+			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 (brew_hot) {
+			st->mstate = BREWING_HOT;
+			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_HOT) {
+		/* Stop brewing if no longer pressing the brew button or we
+		 * exceed the brew max time */
+		if (!brew_hot || millis() - st->brewing_t0 > brewing_max_time) {
+			st->mstate = COOLING;
+			st->cooling_t0 = millis();
+			Serial.println("cooling");
+		}
+	} else if (st->mstate == BREWING_COLD) {
+		/* FIXME: Use cold button instead */
+		if (!brew_hot) {
+			st->mstate = SLEEPING;
+			Serial.println("going back to sleeping after cold brewing");
+		}
+	} 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");
+		}
+	} else if (st->mstate == PANIC_OVERHEAT) {
+		/* Wait until it cools down and enough time has passed */
+		if (st->ntc_T < TIME_OVERHEAT_TEMP &&
+				millis() - st->overheat_t0 > TIME_OVERHEAT_COOL) {
+			st->mstate = SLEEPING;
+			Serial.println("sleeping");
+		}
+	}
 }
 
 void
-update_leds()
+proc_buzz(struct state *st)
 {
-  static int r = 0;
-  static int g = 0;
+	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);
+	}
+}
 
-  if (state == HEATING || state == COOLING) {
-      analogWrite(PIN_LED_RED, r);
-      setled(PIN_LED_GREEN, 0);
-      if (r >= 255)
-        r = 0;
-      else
-        r += 3;
-  } else if (state == HOT) {
-      setled(PIN_LED_RED, 0);
-      setled(PIN_LED_GREEN, 1);
-      r = 0;
-  } else if (state == 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 do_proc(struct state *st, const struct input *input)
+{
+	proc_ntc(st, input);
+	proc_buttons(st, input);
+	proc_machine(st);
+	proc_buzz(st);
 }
 
 void
-update_heater()
+output_leds(const struct state *st)
 {
-  if (state == HEATING || state == HOT || state == BREWING) {
-    int temp = analogRead(PIN_NTC);
-    if (temp < TEMP_MIN)
-      relay(PIN_HEAT, ON);
-    else if (temp > TEMP_MAX)
-      relay(PIN_HEAT, OFF);
-  } else {
-      relay(PIN_HEAT, OFF);
-  }
+	unsigned long t = millis();
+
+	if (st->mstate == SLEEPING) {
+		led_off(&st->red_led);
+		led_off(&st->green_led);
+	} else if (st->mstate == HEATING) {
+		led_off(&st->red_led);
+		led_pattern(&st->green_led, t, 1000UL, "000123456789abcdefff");
+	} else if (st->mstate == COOLING) {
+		led_off(&st->red_led);
+		led_pattern(&st->green_led, t, 1000UL, "fffedcba987654321000");
+	} else if (st->mstate == HOT) {
+		led_off(&st->red_led);
+		led_on(&st->green_led);
+	} else if (st->mstate == PANIC_OVERHEAT) {
+		led_pattern(&st->red_led,   t, 3000UL, "f0f0f0000000");
+		led_pattern(&st->green_led, t, 3000UL, "000000f0f0f0");
+	} else if (st->mstate == BREWING_HOT || st->mstate == BREWING_COLD) {
+		led_off(&st->red_led);
+		led_pattern(&st->green_led, millis(), 2000UL, "0123456789abcdefedcba9876543210");
+	} else {
+		led_off(&st->red_led);
+		led_off(&st->green_led);
+	}
+
+	analogWrite(PIN_LED_RED, led_level(&st->red_led, t));
+	analogWrite(PIN_LED_GREEN, led_level(&st->green_led, t));
 }
 
 void
-update_pump()
+output_relays(const struct state *st)
 {
-	if (state == BREWING) {
+	unsigned long t = millis();
+
+	/* First configure thermostate */
+	if (st->mstate == HEATING || st->mstate == HOT || st->mstate == BREWING_HOT)
+		thermostat_set(&st->thermostat, TEMP_HOT+5.0);
+	else
+		thermostat_off(&st->thermostat);
+
+	/* Then update heater state from thermostate */
+	float T = st->ntc_T;
+	float dT_dt = overheat_speed(&st->overheat);
+	float u = thermostat_state(&st->thermostat, T, dT_dt);
+	heater_on(&st->heater, t, u);
+
+	/* Then switch relays accordingly */
+	int heater_relay_st = heater_state(&st->heater, t);
+	if (heater_relay_st)
+		relay(PIN_HEAT, ON);
+	else
+		relay(PIN_HEAT, OFF);
+
+	int pump_relay_st = 0;
+	if (st->mstate == BREWING_HOT || st->mstate == BREWING_COLD)
+		pump_relay_st = 1;
+
+	if (pump_relay_st)
 		relay(PIN_PUMP, ON);
-  } else {
+	else
 		relay(PIN_PUMP, OFF);
-  }
+
+	Serial.print(t);
+	Serial.print(" ");
+	Serial.print(st->mstate);
+	Serial.print(" ");
+	Serial.print(T);
+	Serial.print(" ");
+	Serial.print(u);
+	Serial.print(" ");
+	Serial.print(heater_relay_st);
+	Serial.print(" ");
+	Serial.println(pump_relay_st);
 }
 
-void
-update_buzz()
+void do_output(const struct state *st)
 {
-  static unsigned long started = 0;
-
-  if (buzz_state == BUZZ_HEY) {
-    tone(PIN_BUZZ, 1500);
-    if (started == 0)
-      started = millis();
-    else if (millis() - started > 20) {
-      buzz_state = BUZZ_OFF;
-    }
-  } else if (buzz_state == BUZZ_STOP) {
-    tone(PIN_BUZZ, 220);
-  } else if (buzz_state == BUZZ_OFF) {
-    noTone(PIN_BUZZ);
-    started = 0;
-  }
+	output_leds(st);
+	output_relays(st);
 }
 
 void setup()
 {
+	wdt_disable();
 	Serial.begin(9600);
 	Serial.println("Booting");
 
@@ -331,21 +408,22 @@ void setup()
 	pinMode(PIN_HEAT, OUTPUT);
 	pinMode(PIN_PUMP, OUTPUT);
 
-  /* Turn all relays off */
-  relay(PIN_HEAT, OFF);
-  relay(PIN_PUMP, OFF);
+	/* Turn all relays off */
+	relay(PIN_HEAT, OFF);
+	relay(PIN_PUMP, OFF);
+
+	overheat_init(&g_st.overheat);
 
 	Serial.println("Ready");
+	wdt_enable(WDTO_250MS);
 }
 
 void loop()
 {
-	//Serial.println("Looping...");
-	update_buttons();
-	progress();
-  update_leds();
-  update_heater();
-  update_pump();
-  update_buzz();
-  delay(5);
+	do_input(&g_in);
+	do_proc(&g_st, &g_in);
+	do_output(&g_st);
+
+	delay(5);
+	wdt_reset();
 }

barista/data/overheat-cutoff.csv

@@ -0,0 +1,959 @@
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barista/heater.c

@@ -0,0 +1,70 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include "heater.h"
+
+#define HEATER_MIN	 500UL /* ms */
+#define HEATER_MAX	2000UL /* ms */
+#define HEATER_PERIOD	5000UL /* ms */
+
+void
+heater_on(struct heater *h, unsigned long t_ms, float duty)
+{
+	unsigned long dt_on = duty * HEATER_MAX;
+
+	if (dt_on < HEATER_MIN)
+		dt_on = 0;
+	else if (dt_on > HEATER_MAX)
+		dt_on = HEATER_MAX;
+
+	h->next_on_dt = dt_on;
+
+	if (h->st == HEATER_OFF) {
+		h->st = HEATER_ON;
+		h->t0_on = t_ms;
+		h->t0_off = t_ms + h->next_on_dt;
+		h->cycle = CYCLE_ON;
+	}
+}
+
+void
+heater_off(struct heater *h)
+{
+	h->st = HEATER_OFF;
+}
+
+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 */
+	while (1) {
+		int changed = 0;
+		if (h->cycle == CYCLE_ON) {
+			if (t_ms >= h->t0_off) {
+				h->cycle = CYCLE_OFF;
+				h->t0_on += HEATER_PERIOD;
+				changed = 1;
+			}
+		} else if (h->cycle == CYCLE_OFF) {
+			if (t_ms >= h->t0_on) {
+				/* Compute current cycle t0_off */
+				h->cycle = CYCLE_ON;
+				h->t0_off = h->t0_on + h->next_on_dt;
+				changed = 1;
+			}
+		}
+
+		if (!changed)
+			break;
+	}
+
+	if (h->cycle == CYCLE_ON)
+		return 1;
+
+	return 0;
+}

barista/heater.h

@@ -0,0 +1,39 @@
+/* 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,
+};
+
+enum heater_cycle {
+	CYCLE_ON = 0,
+	CYCLE_OFF,
+};
+
+struct heater {
+	enum heater_state st;
+	enum heater_cycle cycle;
+	unsigned long t0_on; /* current cycle time on */
+	unsigned long t0_off; /* current cycle time off */
+
+	/* Next cycle */
+	unsigned long next_on_dt; /* in ms */
+};
+
+void heater_on(struct heater *h, unsigned long t_ms, float duty);
+void heater_off(struct heater *h);
+int heater_state(struct heater *h, unsigned long t_ms);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BARISTA_HEATER_H */

barista/led.c

@@ -0,0 +1,71 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include "led.h"
+#include <string.h>
+
+void led_on(struct led *led)
+{
+	led->mode = LED_ON;
+}
+
+void led_off(struct led *led)
+{
+	led->mode = LED_OFF;
+}
+
+void led_pattern(struct led *led, unsigned long t_ms, unsigned long period_ms, const char *pattern)
+{
+	int n = strlen(pattern);
+	unsigned long step_ms = period_ms / n;
+
+	/* Don't change the current state */
+	if (led->mode == LED_PATTERN &&
+			led->step_ms == step_ms &&
+			led->pattern == pattern)
+		return;
+
+	led->mode = LED_PATTERN;
+	led->pat_i = 0;
+	led->pat_n = n;
+	led->pattern = pattern;
+	led->step_ms = step_ms;
+	led->t_ms = t_ms;
+}
+
+/* Return led level brightness in [0, 255] at current time */
+int led_level(struct led *led, unsigned long t_ms)
+{
+	if (led->mode == LED_OFF)
+		return 0;
+
+	if (led->mode == LED_ON)
+		return 255;
+
+	if (led->mode == LED_PATTERN) {
+		while (led->t_ms + led->step_ms < t_ms) {
+			led->t_ms += led->step_ms;
+			led->pat_i++;
+			if (led->pat_i >= led->pat_n)
+				led->pat_i = 0;
+		}
+
+		int c = led->pattern[led->pat_i];
+		int level;
+
+		if (c >= '0' && c <= '9')
+			level = 17 * (c - '0');
+		else
+			level = 17 * (10 + (c - 'a'));
+
+		if (level < 0)
+			level = 0;
+		else if (level > 255)
+			level = 255;
+
+		return level;
+	}
+
+	/* Unknown mode, turn off */
+	return 0;
+}

barista/led.h

@@ -0,0 +1,35 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#ifndef BARISTA_LED_H
+#define BARISTA_LED_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+enum led_mode {
+	LED_OFF = 0,
+	LED_ON,
+	LED_PATTERN,
+};
+
+struct led {
+	enum led_mode mode;
+	const char *pattern;
+	int pat_i;
+	int pat_n;
+	unsigned long step_ms;
+	unsigned long t_ms;
+};
+
+void led_on(struct led *led);
+void led_off(struct led *led);
+void led_pattern(struct led *led, unsigned long t_ms, unsigned long period_ms, const char *pattern);
+int led_level(struct led *led, unsigned long t_ms);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BARISTA_LED_H */

barista/ntc.c

@@ -0,0 +1,44 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include <math.h>
+
+/* Steinhart-Hart Thermistor Coefficients, used to convert resistance into
+ * temperature.
+ *
+ * The current NTC sensor has 102kOhm at 24C but I don't know the specific
+ * model, so the coefficients are computed for this NTC sensor instead:
+ * https://www.tme.eu/Document/f9d2f5e38227fc1c7d979e546ff51768/NTCM-100K-B3950.pdf
+ *
+ * The table seems to match what I would expect. Their R2 resistor is 6.8 kOhm,
+ * which yields a cuttof temperature of around 98.5 C at exactly half voltage
+ * (where the ADC would have more precision).
+ *
+ * In any case, we can calibrate the original NTC sensor by taking three
+ * temperature points. See:
+ * https://www.thinksrs.com/downloads/programs/therm%20calc/ntccalibrator/ntccalculator.html
+ */
+#define C1	0.7740577674e-3
+#define C2	2.073449619e-4
+#define C3	1.263502259e-7
+
+/* Return the temperature in celsisus */
+float
+ntc_temp(float R)
+{
+	/* Computing the log is slow, we may want to build a table */
+	float logR = log(R);
+	float T = (1.0 / (C1 + C2*logR + C3*logR*logR*logR));
+	float Tc = T - 273.15;
+	return Tc;
+}
+
+/* Return resistance in Ohms */
+float
+ntc_resistance(int Vo)
+{
+	float R1 = 10.0e3; /* Resistor for voltage divider */
+	float R2 = R1 * (1023.0 / (float)Vo - 1.0);
+
+	return R2;
+}

barista/ntc.h

@@ -0,0 +1,18 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#ifndef BARISTA_NTC_H
+#define BARISTA_NTC_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+float ntc_resistance(int Vo);
+float ntc_temp(float omhs);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BARISTA_NTC_H */

barista/overheat.c

@@ -0,0 +1,61 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include "overheat.h"
+#include <string.h>
+
+void
+overheat_init(struct overheat *o)
+{
+	memset(o, 0, sizeof(struct overheat));
+}
+
+void
+overheat_input(struct overheat *o, unsigned long t_ms, float temp)
+{
+	unsigned long delta = t_ms - o->last_time;
+
+	if (delta < OVH_INTERVAL)
+		return;
+
+	/* If already go n samples, recompute delta and speed */
+	if (o->n == OVH_NSAMPLES) {
+		float last_T = o->temp[o->next];
+		float last_t = o->t[o->next];
+		float dt = (float) (t_ms - last_t) * 1e-3;
+		o->delta = temp - last_T;
+		o->speed = o->delta / dt;
+	}
+
+	/* Add the new sample */
+	o->temp[o->next] = temp;
+	o->t[o->next] = t_ms;
+	o->next++;
+	if (o->next >= OVH_NSAMPLES)
+		o->next = 0;
+	if (o->n < OVH_NSAMPLES)
+		o->n++;
+
+	o->last_time = t_ms;
+}
+
+float
+overheat_delta(struct overheat *o)
+{
+	return o->delta;
+}
+
+float
+overheat_speed(struct overheat *o)
+{
+	return o->speed;
+}
+
+int
+overheat_panic(struct overheat *o)
+{
+	if (o->speed > OVH_THRESHOLD)
+		return 1;
+	else
+		return 0;
+}

barista/overheat.h

@@ -0,0 +1,35 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#ifndef BARISTA_OVERHEAT_H
+#define BARISTA_OVERHEAT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define OVH_NSAMPLES	20
+#define OVH_INTERVAL	200 /* ms */
+#define OVH_THRESHOLD	2.0 /* °C / s */
+
+struct overheat {
+	unsigned long last_time;
+	float temp[OVH_NSAMPLES];
+	long unsigned t[OVH_NSAMPLES];
+	int next;
+	int n;
+	float delta;
+	float speed;
+};
+
+void overheat_init(struct overheat *o);
+void overheat_input(struct overheat *o, unsigned long t_ms, float temp);
+float overheat_delta(struct overheat *o);
+float overheat_speed(struct overheat *o);
+int overheat_panic(struct overheat *o);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BARISTA_OVERHEAT_H */

barista/pinout.h

@@ -0,0 +1,78 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#ifndef BARISTA_PINOUT_H
+#define BARISTA_PINOUT_H
+
+#include <Arduino.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/*
+ *                             ATmega328p
+ *                            +---------+
+ *  (PCINT14/RESET)      PC6 -|1  \_/ 28|- PC5 (ADC5/SCL/PCINT13)
+ *  (PCINT16/RXD)        PD0 -|2      27|- PC4 (ADC4/SDA/PCINT12)
+ *  (PCINT17/TXD)        PD1 -|3      26|- PC3 (ADC3/PCINT11)
+ *  (PCINT18/INT0)       PD2 -|4      25|- PC2 (ADC2/PCINT10)
+ *  (PCINT19/OC2B/INT1)  PD3 -|5      24|- PC1 (ADC1/PCINT9)
+ *  (PCINT20/XCK/T0)     PD4 -|6      23|- PC0 (ADC0/PCINT8)
+ *  VCC                      -|7      22|-     GND
+ *  GND                      -|8      21|-     AREF
+ *  (PCINT6/XTAL1/TOSC1) PB6 -|9      20|-     AVCC
+ *  (PCINT7/XTAL2/TOSC2) PB7 -|10     19|- PB5 (SCK/PCINT5)
+ *  (PCINT21/OC0B/T1)    PD5 -|11     18|- PB4 (MISO/PCINT4)
+ *  (PCINT22/OC0A/AIN0)  PD6 -|12     17|- PB3 (MOSI/OC2A/PCINT3)
+ *  (PCINT23/AIN1)       PD7 -|13     16|- PB2 (SS/OC1B/PCINT2)
+ *  (PCINT0/CLKO/ICP1)   PB0 -|14     15|- PB1 (OC1A/PCINT1)
+ *                            +---------+
+ *
+ * 
+ *         ATMEL ATMEGA8 & 168 / ARDUINO
+ *
+ *                          +-\/-+
+ *                    PC6  1|    |28  PC5 (AI 5)
+ *              (D 0) PD0  2|    |27  PC4 (AI 4)
+ *              (D 1) PD1  3|    |26  PC3 (AI 3)
+ *              (D 2) PD2  4|    |25  PC2 (AI 2)
+ *         PWM+ (D 3) PD3  5|    |24  PC1 (AI 1)
+ *              (D 4) PD4  6|    |23  PC0 (AI 0)
+ *                    VCC  7|    |22  GND
+ *                    GND  8|    |21  AREF
+ *                    PB6  9|    |20  AVCC
+ *                    PB7 10|    |19  PB5 (D 13)
+ *         PWM+ (D 5) PD5 11|    |18  PB4 (D 12)
+ *         PWM+ (D 6) PD6 12|    |17  PB3 (D 11) PWM
+ *              (D 7) PD7 13|    |16  PB2 (D 10) PWM
+ *              (D 8) PB0 14|    |15  PB1 (D 9) PWM
+ *                          +----+
+ *
+ *
+ */
+
+enum pinout {
+	/* Inputs */
+	PIN_POWER_ON  = 8,
+	PIN_HOT       = 9,
+	//PIN_FLOW      = PIN_D5,
+
+	/* Outputs */
+	PIN_LED_GREEN = 5,
+	PIN_LED_RED   = 6,
+	PIN_HEAT      = 7,
+	PIN_PUMP      = 12,
+	PIN_BUZZ      = 10,
+
+	/* Analog */
+	PIN_NTC       = PIN_A0,
+};
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BARISTA_PINOUT_H */

barista/test/Makefile

@@ -0,0 +1 @@
+test_ntc: test_ntc.o ../ntc.c

barista/test/compat.c

@@ -0,0 +1,13 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include "compat.h"
+#include <time.h>
+
+unsigned long millis(void)
+{
+	struct timespec ts;
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+
+	return ts.tv_sec * 1000UL + ts.tv_nsec / 1000000UL;
+}

barista/test/compat.h

@@ -0,0 +1,17 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#ifndef BARISTA_COMPAT_H
+#define BARISTA_COMPAT_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+unsigned long millis(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BARISTA_COMPAT_H */

barista/test/test_led.c

@@ -0,0 +1,42 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include <stdio.h>
+#include "led.h"
+#include "compat.h"
+
+int main(void)
+{
+	struct led led;
+	unsigned long t0 = millis();
+	unsigned long step = 1000UL;
+
+	led_pattern(&led, t0, step, "000123456789abcdefff");
+
+	int last_level = -1;
+
+	unsigned long last_t = millis();
+	while (1) {
+		unsigned long t = millis();
+
+		if (t - t0 >= 10000UL)
+			break;
+
+		if (t - last_t < 50UL)
+			continue;
+
+		int level = led_level(&led, millis());
+		printf("|");
+		for (int i = 0; i < 256; i+=4) {
+			if (i < level)
+				printf("=");
+			else
+				printf(" ");
+		}
+		printf("|\n");
+		last_level = level;
+		last_t = t;
+	}
+
+	return 0;
+}

barista/test/test_ntc.c

@@ -0,0 +1,18 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include <stdio.h>
+#include "ntc.h"
+
+int main(void)
+{
+	for (int i = 0; i <= 1023; i++) {
+		float R = ntc_resistance(i);
+		float T = ntc_temp(R);
+		if (T < 96.0 || T > 100.2)
+			continue;
+
+		printf("%6d  %12.1f Ohm  %12.1f C\n", i, R, T);
+	}
+	return 0;
+}

barista/test/test_overheat.c

@@ -0,0 +1,36 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include <stdio.h>
+#include "overheat.h"
+
+/* Read a CSV from the stdin in the format
+ * <time_in_seconds> <state> <temp_in_C>
+ * skipping the first row (header).
+ *
+ * Outputs overheat state. */
+
+#define MAX_LINE 1024
+
+int main(void)
+{
+	char buf[MAX_LINE];
+	fgets(buf, MAX_LINE, stdin);
+
+	float t, temp;
+	int st;
+
+	struct overheat ovh;
+	overheat_init(&ovh);
+
+	while (scanf("%f %d %f", &t, &st, &temp) == 3) {
+
+		overheat_input(&ovh, t * 1000.0, temp);
+		float delta = overheat_delta(&ovh);
+		int panic = overheat_panic(&ovh);
+
+		printf("%.3f %d %.2f %.1f %s\n", t, st, temp, delta, panic ? "PANIC" : "OK");
+	}
+
+	return 0;
+}

barista/test/test_thermostat.c

@@ -0,0 +1,49 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include <stdio.h>
+#include "overheat.h"
+#include "thermostat.h"
+#include "heater.h"
+
+/* Read a CSV from the stdin in the format
+ * <time_in_seconds> <state> <temp_in_C>
+ * skipping the first row (header).
+ *
+ * Outputs overheat state. */
+
+#define MAX_LINE 1024
+
+int main(void)
+{
+	char buf[MAX_LINE];
+	fgets(buf, MAX_LINE, stdin);
+
+	float t, temp;
+	int st;
+
+	struct overheat ovh = { 0 };
+	struct thermostat th = { 0 };
+	struct heater heater = { 0 };
+
+	overheat_init(&ovh);
+
+	for (int i = 0; scanf("%f %d %f", &t, &st, &temp) == 3; i++) {
+		if (i == 0)
+			thermostat_set(&th, 60.0);
+
+		unsigned long t_ms = t * 1000;
+
+		overheat_input(&ovh, t_ms, temp);
+		float delta = overheat_delta(&ovh);
+		float speed = overheat_speed(&ovh);
+		float u = thermostat_state(&th, temp, speed);
+		heater_on(&heater, t_ms, u);
+		int h = heater_state(&heater, t_ms);
+		int panic = overheat_panic(&ovh);
+
+		printf("%8.3f %2d %6.2f %6.1f %8.3f %8.3f %d %s\n", t, st, temp, delta, speed, u, h, panic ? "PANIC" : "OK");
+	}
+
+	return 0;
+}

barista/thermostat.c

@@ -0,0 +1,64 @@
+/* Copyright (c) 2025 Rodrigo Arias Mallo <rodarima@gmail.com>
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include "thermostat.h"
+
+#define TEMP_MIN	35.0 /* °C */
+#define DELTA_LOW	1.0
+#define DELTA_HIGH	1.0
+
+#define T_ERR_MIN	35.0 /* °C */
+
+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;
+}
+
+static float
+pid(float T0, float T, float dT_dt)
+{
+	float err_min = 2.0;
+
+	/* The rate of change of error is the same as the temperature, as they
+	 * are only offset by a mostly constant value */
+	float derr_dt = dT_dt;
+
+	if ((T0 - T) < err_min)
+		return 0.0;
+
+	float Kp = 1.0 / 20.0;
+	float Kd = - 1.0 / 3.0;
+	float u = Kp * (T0 - T) + Kd * dT_dt;
+
+	if (u < 0.0)
+		u = 0.0;
+	else if (u > 1.0)
+		u = 1.0;
+
+	return u;
+}
+
+/* Return a value in [0, 1] to set the heater duty cycle */
+float
+thermostat_state(struct thermostat *th, float T, float dT_dt)
+{
+	if (th->st == THERMOSTAT_OFF)
+		return 0.0;
+
+	return pid(th->temp_target, T, dT_dt);
+}

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);
+float thermostat_state(struct thermostat *th, float T, float dT_dt);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* BARISTA_THERMOSTAT_H */