Build a Smart Ultrasonic Distance Scale with Arduino

1// Ultrasonic → SH110x OLED (I2C) Demo
2// Works with SH1106/SH1107 128x64 modules using Adafruit SH110X + GFX
3
4#include <Adafruit_GFX.h>
5#include <Adafruit_SH110X.h>
6#include <Wire.h>
7
8// ===== OLED CONFIG =====
9#define SCREEN_WIDTH 128
10#define SCREEN_HEIGHT 64
11#define OLED_ADDR 0x3C          // Common: 0x3C (sometimes 0x3D)
12
13// For SH1106 (most 128x64 I2C modules):
14Adafruit_SH1106G display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);
15// If your panel is SH1107, use:
16// Adafruit_SH1107 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire);
17
18// ===== ULTRASONIC CONFIG =====
19// HC-SR04 pins
20const int PIN_TRIG = 9;
21const int PIN_ECHO = 10;
22
23// Measurement params
24const unsigned long ECHO_TIMEOUT_US = 30000UL;  // ~5m max (sound one-way ~0.0343 cm/us)
25const uint8_t SAMPLES = 5;                      // simple moving average
26
27// ===== HELPERS =====
28float measureDistanceCm() {
29  // Trigger a 10 µs pulse
30  digitalWrite(PIN_TRIG, LOW);
31  delayMicroseconds(2);
32  digitalWrite(PIN_TRIG, HIGH);
33  delayMicroseconds(10);
34  digitalWrite(PIN_TRIG, LOW);
35
36  // Read echo pulse width
37  unsigned long duration = pulseIn(PIN_ECHO, HIGH, ECHO_TIMEOUT_US);
38  if (duration == 0) return NAN; // timeout/no object
39
40  // distance = (duration_us * speed_of_sound_cm_per_us) / 2
41  // speed of sound ≈ 0.0343 cm/us at ~20°C
42  return (duration * 0.0343f) / 2.0f;
43}
44
45float cmToIn(float cm) {
46  return cm * 0.393700787f;
47}
48
49float avgDistanceCm(uint8_t n = SAMPLES) {
50  float sum = 0;
51  uint8_t good = 0;
52  for (uint8_t i = 0; i < n; i++) {
53    float d = measureDistanceCm();
54    if (!isnan(d)) { sum += d; good++; }
55    delay(20);
56  }
57  if (good == 0) return NAN;
58  return sum / good;
59}
60
61// Draws a horizontal bar (0–maxVal) across the width
62void drawBar(float value, float maxVal) {
63  if (isnan(value) || maxVal <= 0) return;
64  int w = map((int)(value * 100), 0, (int)(maxVal * 100), 0, SCREEN_WIDTH - 4);
65  w = constrain(w, 0, SCREEN_WIDTH - 4);
66  // outline
67  display.drawRect(2, 48, SCREEN_WIDTH - 4, 12, SH110X_WHITE);
68  // fill
69  if (w > 0) display.fillRect(3, 49, w, 10, SH110X_WHITE);
70}
71
72void setup() {
73  pinMode(PIN_TRIG, OUTPUT);
74  pinMode(PIN_ECHO, INPUT);
75
76  Wire.begin();
77  // For some boards, you may need Wire.setClock(400000);
78
79  display.begin(OLED_ADDR, true);  // true = reset
80  display.clearDisplay();
81
82  display.setTextColor(SH110X_WHITE);
83  display.setTextSize(1);
84  display.setCursor(0, 0);
85  display.println(F("SH110x Ultrasonic"));
86  display.println(F("Initializing..."));
87  display.display();
88  delay(800);
89}
90
91void loop() {
92  float cm = avgDistanceCm();
93  float in_ = cmToIn(cm);
94
95  display.clearDisplay();
96
97  // Title
98  display.setTextSize(1);
99  display.setCursor(0, 0);
100  display.print(F("Ultrasonic Distance"));
101
102  if (isnan(cm)) {
103    display.setCursor(0, 20);
104    display.setTextSize(2);
105    display.println(F("No echo"));
106    display.setTextSize(1);
107    display.setCursor(0, 40);
108    display.println(F("Check wiring/aim"));
109  } else {
110    // Big number (cm)
111    display.setTextSize(2);
112    display.setCursor(0, 18);
113    display.print(cm, 1);
114    display.print(F(" cm"));
115
116    // Smaller line (inches)
117    display.setTextSize(1);
118    display.setCursor(0, 40);
119    display.print(in_, 2);
120    display.println(F(" in"));
121
122    // Bar graph up to a chosen max (e.g., 200 cm)
123    drawBar(cm, 200.0f);
124  }
125
126  display.display();
127  delay(120);
128}