Thermometer + Clock in a 3D-Printed Case

// Room thermometer with a screen, using parts from the Elegoo kit.//// Temperature sensor (DHT11): plugged straight into A0, A1 and A2, either way// round. The middle pin (power) lands in A1, which this program sets HIGH.// Of the two outside pins, one is ground and one is the data line; the// program tries both ways and keeps the one that works.//// Screen (LCD1602), pin by pin. Pin 1 is the one marked VSS://    1 VSS -> GND         2 VDD -> 5V          3 V0 -> pin 9       4 RS -> pin 12//    5 RW  -> GND         6 E   -> pin 11      7 to 10 -> nothing//   11 D4  -> pin 5      12 D5  -> pin 4      13 D6 -> pin 3      14 D7 -> pin 2//   15 A   -> pin 10     16 K   -> GND//// Top row: temperature and humidity. Bottom row: a clock. The computer sets// the clock; after that the Arduino keeps counting on its own, including on// the 9V battery. To switch to the battery without losing the time, plug the// battery into the round power socket first, then unplug the USB cable.//// From the computer://   "T 14:30:00" sets the clock//   "?"          asks what time the clock thinks it is//   "c 40"       sets the screen contrast, 0 to 255 (lower = darker letters)//   "b 160"      sets the backlight brightness, 0 to 255//   "o -6.5"     sets a correction in degrees F, to match a real thermometer// Contrast, backlight and correction are saved, so they stay the same on battery.#include <EEPROM.h>// ---------- Pins ----------const byte SENSOR_POWER = A1;const byte SENSOR_ENDS[2] = {A0, A2};const byte LCD_RS = 12;const byte LCD_E = 11;const byte LCD_DATA[4] = {5, 4, 3, 2};  // the screen's D4, D5, D6, D7const byte LCD_CONTRAST = 9;const byte LCD_LIGHT = 10;// ---------- Saved settings ----------struct Settings {  byte check;  byte contrast;  byte backlight;  float offsetF;};const byte SETTINGS_CHECK = 0x5A;Settings settings;// ---------- Clock ----------// The time lives in a part of memory that a reset doesn't wipe, so it// survives a press of the reset button (but not losing power).const unsigned long CLOCK_CHECK = 0xC10C4321;unsigned long clockCheck __attribute__((section(".noinit")));long secondsToday __attribute__((section(".noinit")));unsigned long lastTickMicros;long lastClockShown = -1;byte dataPin = A0;byte groundPin = A2;bool sensorFound = false;unsigned long lastReading = 0;void setup() {  Serial.begin(9600);  Serial.println("Thermometer starting");  EEPROM.get(0, settings);  if (settings.check != SETTINGS_CHECK) {    settings = {SETTINGS_CHECK, 40, 160, 0.0};    EEPROM.put(0, settings);  }  // Pins 9 and 10 flicker on and off very fast to set contrast and brightness.  // Making them flicker faster (31,000 times a second) keeps the screen steady.  TCCR1B = (TCCR1B & 0b11111000) | 0b001;  pinMode(LCD_CONTRAST, OUTPUT);  pinMode(LCD_LIGHT, OUTPUT);  analogWrite(LCD_CONTRAST, settings.contrast);  analogWrite(LCD_LIGHT, settings.backlight);  if (clockCheck != CLOCK_CHECK || secondsToday < 0 || secondsToday >= 86400L) {    clockCheck = 0;  // no time yet: the clock shows --:-- until the computer sends it    secondsToday = 0;  }  lastTickMicros = micros();  lcdBegin();  lcdPrintAt(0, 0, "Thermometer     ");  showClock();  pinMode(SENSOR_POWER, OUTPUT);  digitalWrite(SENSOR_POWER, HIGH);  pinMode(LED_BUILTIN, OUTPUT);}void loop() {  readComputer();  keepTime();  if (secondsToday != lastClockShown) showClock();  if (millis() - lastReading >= 5000 || lastReading == 0) updateReading();}// ---------- Clock ----------// Counts the seconds using the Arduino's own timer.void keepTime() {  while (micros() - lastTickMicros >= 1000000UL) {    lastTickMicros += 1000000UL;    secondsToday = (secondsToday + 1) % 86400L;  }}// Shows e.g. "3:45:12 PM" in the middle of the bottom row.void showClock() {  lastClockShown = secondsToday;  char time[12], line[17];  if (clockCheck == CLOCK_CHECK) {    int hours = secondsToday / 3600;    int hours12 = hours % 12 == 0 ? 12 : hours % 12;    snprintf(time, sizeof(time), "%d:%02d:%02d %s", hours12, (int)(secondsToday / 60 % 60),             (int)(secondsToday % 60), hours < 12 ? "AM" : "PM");  } else {    strcpy(time, "--:--");  }  byte length = strlen(time);  byte left = (16 - length) / 2;  memset(line, ' ', 16);  memcpy(line + left, time, length);  line[16] = '\0';  lcdPrintAt(0, 1, line);}// ---------- Temperature ----------void updateReading() {  lastReading = millis();  if (lastReading == 0) lastReading = 1;  byte reading[5];  bool ok;  if (!sensorFound) {    // Try the data line on each outside pin, with the other one as ground.    ok = false;    for (byte i = 0; i < 2 && !ok; i++) {      useSensorWiring(SENSOR_ENDS[i], SENSOR_ENDS[1 - i]);      delay(1500);  // the sensor needs a moment after it gets power      ok = readSensor(reading);    }    sensorFound = ok;  } else {    ok = readSensor(reading);  }  // Repeat the screen's start-up routine before every update, so a screen  // that got power late (or had a glitch) gets back in step.  lcdWake();  if (!ok) {    Serial.println("Can't read the sensor. Is it plugged into A0, A1 and A2?");    lcdPrintAt(0, 0, "Sensor? A0 A1 A2");    showClock();    return;  }  float celsius = reading[2] + reading[3] / 10.0;  float fahrenheit = celsius * 9 / 5 + 32 + settings.offsetF;  byte humidity = reading[0];  Serial.print("Temperature: ");  Serial.print(fahrenheit, 1);  Serial.print(" F   Humidity: ");  Serial.print(humidity);  Serial.println("%");  showReading(fahrenheit, humidity);  showClock();  digitalWrite(LED_BUILTIN, HIGH);  delay(100);  digitalWrite(LED_BUILTIN, LOW);}// Shows e.g.   72.5°F  45%void showReading(float fahrenheit, byte humidity) {  char f[8], line[17];  dtostrf(fahrenheit, 4, 1, f);  snprintf(line, sizeof(line), "  %s\xDF" "F  %d%%", f, humidity);  byte length = strlen(line);  while (length < 16) line[length++] = ' ';  // blank out anything left over  line[16] = '\0';  lcdPrintAt(0, 0, line);}// ---------- Settings from the computer ----------void printTime() {  if (clockCheck != CLOCK_CHECK) {    Serial.println("Clock not set");    return;  }  char text[9];  sprintf(text, "%02d:%02d:%02d", (int)(secondsToday / 3600),          (int)(secondsToday / 60 % 60), (int)(secondsToday % 60));  Serial.println(text);}void readComputer() {  static char line[20];  static byte length = 0;  while (Serial.available()) {    char ch = Serial.read();    if (ch == '\n' || ch == '\r') {      line[length] = '\0';      if (length > 0) handleCommand(line);      length = 0;    } else if (length < sizeof(line) - 1) {      line[length++] = ch;    }  }}void handleCommand(const char *line) {  int h, m, s;  if (sscanf(line, "T %d:%d:%d", &h, &m, &s) == 3 &&      h >= 0 && h < 24 && m >= 0 && m < 60 && s >= 0 && s < 60) {    secondsToday = h * 3600L + m * 60L + s;    lastTickMicros = micros();    clockCheck = CLOCK_CHECK;    showClock();    Serial.print("Clock set to ");    printTime();    return;  }  if (line[0] == '?') {    printTime();    return;  }  float value = atof(line + 1);  if (line[0] == 'c') {    settings.contrast = constrain((int)value, 0, 255);    analogWrite(LCD_CONTRAST, settings.contrast);  } else if (line[0] == 'b') {    settings.backlight = constrain((int)value, 0, 255);    analogWrite(LCD_LIGHT, settings.backlight);  } else if (line[0] == 'o') {    settings.offsetF = value;    lastReading = 0;  // show the corrected temperature straight away  } else {    return;  }  EEPROM.put(0, settings);  Serial.print("Saved: contrast ");  Serial.print(settings.contrast);  Serial.print(", backlight ");  Serial.print(settings.backlight);  Serial.print(", correction ");  Serial.print(settings.offsetF, 1);  Serial.println(" F");}// ---------- Temperature sensor ----------void useSensorWiring(byte data, byte ground) {  dataPin = data;  groundPin = ground;  pinMode(groundPin, OUTPUT);  digitalWrite(groundPin, LOW);  pinMode(dataPin, INPUT_PULLUP);}// Asks the sensor for a reading. It answers with 40 quick pulses: a short// pulse is a 0 and a long one is a 1. The 5 bytes are humidity, humidity// tenths, temperature, temperature tenths, and a check number.bool readSensor(byte data[5]) {  for (byte i = 0; i < 5; i++) data[i] = 0;  pinMode(dataPin, OUTPUT);  digitalWrite(dataPin, LOW);  // "wake up" signal  delay(20);  pinMode(dataPin, INPUT_PULLUP);  if (!waitFor(LOW, 200) || !waitFor(HIGH, 200) || !waitFor(LOW, 200)) return false;  for (byte bit = 0; bit < 40; bit++) {    if (!waitFor(HIGH, 200)) return false;    unsigned long start = micros();    if (!waitFor(LOW, 200)) return false;    data[bit / 8] <<= 1;    if (micros() - start > 45) data[bit / 8] |= 1;  }  return data[4] == (byte)(data[0] + data[1] + data[2] + data[3]);}bool waitFor(byte level, unsigned int timeoutMicros) {  unsigned long start = micros();  while (digitalRead(dataPin) != level) {    if (micros() - start > timeoutMicros) return false;  }  return true;}// ---------- Screen ----------// The screen takes letters 4 bits at a time on its D4-D7 pins. RS picks// between a command (LOW) and a letter (HIGH), and a pulse on E sends it.void lcdBegin() {  pinMode(LCD_RS, OUTPUT);  pinMode(LCD_E, OUTPUT);  for (byte i = 0; i < 4; i++) pinMode(LCD_DATA[i], OUTPUT);  digitalWrite(LCD_E, LOW);  digitalWrite(LCD_RS, LOW);  delay(50);  // give the screen time to wake up  lcdWake();  lcdSend(0x01, false);  // clear the screen  delay(2);}// The screen's start-up routine: whatever state it's in, this switches it// into 4-bit mode with 2 lines of text. It doesn't clear the screen, so it// can be repeated without any flicker.void lcdWake() {  digitalWrite(LCD_RS, LOW);  lcdNibble(0x3);  delay(5);  lcdNibble(0x3);  delayMicroseconds(150);  lcdNibble(0x3);  delayMicroseconds(150);  lcdNibble(0x2);  delayMicroseconds(150);  lcdSend(0x28, false);  // 2 lines of text  lcdSend(0x0C, false);  // screen on, no cursor  lcdSend(0x06, false);  // move right after each letter}void lcdNibble(byte bits) {  for (byte i = 0; i < 4; i++) digitalWrite(LCD_DATA[i], (bits >> i) & 1);  digitalWrite(LCD_E, HIGH);  delayMicroseconds(1);  digitalWrite(LCD_E, LOW);  delayMicroseconds(100);}void lcdSend(byte value, bool isLetter) {  digitalWrite(LCD_RS, isLetter ? HIGH : LOW);  lcdNibble(value >> 4);  lcdNibble(value & 0x0F);}void lcdPrintAt(byte column, byte row, const char *text) {  lcdSend(0x80 | (column + (row ? 0x40 : 0)), false);  while (*text) lcdSend(*text++, true);}