Smart Cup Coaster

Detail photos

/*

smart cup coaster 

Maggie Guo

Code is written by ChatGPT. It is for Arduino Uno. I set three different sets of thresholds corresponding to three different drinks. Each set includes a lower trigger and an upper trigger. The soundtrack is stored in the SD card. Once the trigger is met, it will play the soundtrack. There is also an extra handleTareEdge() function for zeroing current reading of the weight.

pin mapping as above!

*/

#include <SoftwareSerial.h>

#include <DFRobotDFPlayerMini.h>

#include "HX711.h"

// ---- DFPlayer on D10/D11 ----

SoftwareSerial mp3Serial(10, 11);     // D10=RX, D11=TX

DFRobotDFPlayerMini mp3;

bool dfp_ok = false;

// ---- HX711 on D4/D5 ----

#define HX_DT 4

#define HX_SCK 5

HX711 scale;

// ---- Buttons (wired to GND, use INPUT_PULLUP) ----

#define BTN_A 2   // Profile A: 5g + 100g

#define BTN_B 3   // Profile B: 50g + 100g

#define BTN_C 6   // Profile C: 80g + 100g

// ---- Calibration ----

float CALIBRATION_FACTOR = 7050.0f;

// ---- DFPlayer config ----

const int   TRACK         = 1;        // plays MP3/0001.mp3

const int   START_VOLUME  = 25;       // 0–30 range, 25 is fairly loud

// ---- Profiles ----

struct Profile {

 const char* name;

 float t1_g;

 float t2_g;

};

Profile PROFILES[3] = {

 {"A (5g, 100g)",   5.0f, 100.0f},

 {"B (50g, 100g)", 50.0f, 100.0f},

 {"C (80g, 100g)", 80.0f, 100.0f}

};

int    current_profile = 0;

bool   armed_t1 = true;

bool   armed_t2 = true;

const float REARM_MARGIN_G = 2.0f;   // re-arm when below (min threshold − 2 g)

unsigned long lastBtnCheck = 0;

const unsigned long BTN_DEBOUNCE_MS = 80;

// ---------- Helpers ----------

void printProfileBanner() {

 Serial.println();

 Serial.println(F("========================================"));

 Serial.print(F(" Active Profile: "));

 Serial.println(PROFILES[current_profile].name);

 Serial.println(F(" Lower trigger → plays at first threshold"));

 Serial.println(F(" Upper trigger → plays at 100 g"));

 Serial.println(F("========================================"));

 Serial.println();

}

void selectProfile(int idx) {

 if (idx < 0 || idx > 2) return;

 if (current_profile == idx) return; // already active

 current_profile = idx;

 armed_t1 = true;

 armed_t2 = true;

 printProfileBanner();

}

bool buttonPressed(int pin) {

 return digitalRead(pin) == LOW;

}

void checkButtons() {

 unsigned long now = millis();

 if (now - lastBtnCheck < BTN_DEBOUNCE_MS) return;

 lastBtnCheck = now;

 if (buttonPressed(BTN_A)) {

   selectProfile(0);

 } else if (buttonPressed(BTN_B)) {

   selectProfile(1);

 } else if (buttonPressed(BTN_C)) {

   selectProfile(2);

 }

}

float rearmThresholdFor(Profile p) {

 float base = min(p.t1_g, p.t2_g) - REARM_MARGIN_G;

 return base < 0.0f ? 0.0f : base;

}

// ---------- Setup ----------

void setup() {

 Serial.begin(115200);

 while (!Serial) {}

 pinMode(BTN_A, INPUT_PULLUP);

 pinMode(BTN_B, INPUT_PULLUP);

 pinMode(BTN_C, INPUT_PULLUP);

 Serial.println(F("Boot: HX711 + DFPlayer with 3 selectable trigger profiles"));

 mp3Serial.begin(9600);

 dfp_ok = mp3.begin(mp3Serial);

 if (dfp_ok) {

   mp3.volume(START_VOLUME);

   mp3.EQ(0);

   Serial.println(F("DFPlayer online."));

 } else {

   Serial.println(F("DFPlayer init FAILED (check wiring and SD card)."));

 }

 scale.begin(HX_DT, HX_SCK);

 scale.set_scale(CALIBRATION_FACTOR);

 delay(300);

 Serial.println(F("Place EMPTY CUP on coaster; taring in 2 s..."));

 delay(2000);

 scale.tare(15);

 Serial.println(F("Tare complete."));

 printProfileBanner();

}

// ---------- Main loop ----------

void loop() {

 checkButtons();

 float grams = scale.get_units(5);

 Profile &P = PROFILES[current_profile];

 float t1 = P.t1_g;

 float t2 = P.t2_g;

 float rearmAt = rearmThresholdFor(P);

 Serial.print(F("mass[g]=")); Serial.print(grams, 1);

 Serial.print(F(" | Profile: ")); Serial.print(P.name);

 Serial.print(F(" | t1: ")); Serial.print(armed_t1 ? "armed" : "done");

 Serial.print(F(", t2: ")); Serial.println(armed_t2 ? "armed" : "done");

 if (armed_t1 && grams >= t1) {

   Serial.print(F(">=")); Serial.print(t1, 1); Serial.println(F(" g → PLAY (t1)"));

   if (dfp_ok) mp3.play(TRACK);

   armed_t1 = false;

 }

 if (armed_t2 && grams >= t2) {

   Serial.print(F(">=")); Serial.print(t2, 1); Serial.println(F(" g → PLAY (t2)"));

   if (dfp_ok) mp3.play(TRACK);

   armed_t2 = false;

 }

 if ((!armed_t1 || !armed_t2) && grams <= rearmAt) {

   armed_t1 = true;

   armed_t2 = true;

   Serial.print(F("<= ")); Serial.print(rearmAt, 1); Serial.println(F(" g → re-armed both triggers"));

 }

 if (dfp_ok && mp3.available()) { mp3.readType(); mp3.read(); }

 delay(200);

}