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--- pm:prj2025:eradu:stefan.dascalu2612 [2025/05/20 23:29]
stefan.dascalu2612
+++ pm:prj2025:eradu:stefan.dascalu2612 [2025/05/30 07:54] (current)
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 ==== Introduction ====
 **eSafe** is a digital lockbox implemented on an **Arduino Uno**. It uses a 4×4 matrix keypad for PIN entry, an SG90 servo for a mechanical latch, a DS1307 real-time clock (I²C) to enforce access windows, and a 16×2 I²C LCD to display status and time. Three wrong PIN attempts trigger an alarm tone and flashing red LED; valid entries drive the servo to unlock, light a green LED, and display “UNLOCKED.”
-**This project integrates functionalities from three labs:**
-  * **Lab 2 (Interrupts & GPIO):** keypad row-change detection
-  * **Lab 3 (Timers):** debounce via Timer 2 CTC and alarm timing
-  * **Lab 6 (I²C):** shared bus for LCD and RTC
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@@ Line 26: / Line 20: @@
 ==== Hardware Functionality ====
-  * **Keypad**: row-interrupt + Timer 2 CTC debounce
+  * **Keypad**: polled via Keypad library on GPIO
   * **Buzzer**: tone/noTone alarm, driven directly from Arduino pin
   * **LEDs**: status indicators with resistors
   * **Servo**: 50 Hz PWM; relocked non-blocking after 5 s
   * **LCD/RTC**: HD44780 via PCF8574; DS1307 battery-backed timekeeper
+  * **ADC**: internal 1.1 V band-gap → VCC monitor every 5 s; red LED blinks below 4.6 V
   * **Power**: on-board 5 V regulator (~500 mA); peak draw ~270 mA
 ==== Pin-out Detail ====
 ^ Component          ^ Interface      ^ Arduino pin  ^ Direction  ^ Rationale                                      ^
-| Keypad row/col     | GPIO           | D2–D9        | input      | Pin-change ISR on D2–D5; columns polled on D6–D9 |
+| Keypad row/col     | GPIO           | D2–D9        | input      | Scanned periodically by Keypad library (no interrupts) |
 | Passive buzzer     | GPIO           | D11          | output     | direct drive with tone()/noTone()                |
 | Red LED            | GPIO           | D13          | output     | Built-in LED pin                                 |
@@ Line 42: / Line 37: @@
 | LCD I²C            | I²C (TWI)      | A4/A5        | bidir      | Hardware Wire bus                                |
 | RTC DS1307         | I²C (TWI)      | A4/A5        | bidir      | Shares same TWI bus                              |
+| ADC (VCC monitor)  | internal ch 14 |   —          | input      | 1.1 V band-gap reference                         |
 ==== Bill Of Materials ====
@@ Line 52: / Line 49: @@
 | Breadboard + jumper wires + LEDs + resistors  | https://www.optimusdigital.ro/ro/kituri/12026-kit-plusivo-pentru-introducere-in-electronica-0721248990075.html                                                        |
-==== Photos of the eSafe project ====
+==== Photos and video of the eSafe project ====
 {{esafe1.jpeg?400x}}
 {{esafe2.jpeg?400x}}
 {{esafe3.jpeg?400x}}
-==== Software Design ====
+https://youtube.com/shorts/6ttbbS6FWxo
+==== Software Design ====
 === Implementation Status ===
-  * Full feature set in ~200 lines of C++ on Arduino Uno
+  * ~400 lines of custom C++ on Arduino Uno integrating all core features
-  * PIN entry, servo latch, LEDs, buzzer, I²C LCD & RTC, time window, unlock log
+  * PIN entry with 4×4 matrix scan, three-strike alarm, and time-based lockout fully tested
-  * Stable on hardware; manual end-to-end tests completed
+  * Live clock updates, non-blocking unlock/relock, and persistent last-unlock log verified in hardware
+  * Real-time VCC reading via ADC; value streamed to Serial Monitor and low-battery LED alert
 === Library Choices ===
-^ Library               ^ Purpose                     ^ Justification                                  ^
+| Library             | Purpose                     | Justification                                    |
-| Wire / RTClib         | I²C + DS1307                | Adafruit’s proven RTC driver                   |
+| Wire / RTClib       | I²C bus & DS1307 driver     | proven reliability, minimal API for RTC access   |
-| LiquidCrystal_I2C     | I²C LCD                      | Minimal wiring, easy print interface           |
+| LiquidCrystal_I2C   | HD44780 LCD over I²C        | reduces wiring and boilerplate, easy print() API |
-| Keypad                | 4×4 scan + debounce          | handles interrupts + debouncing                |
+| Keypad              | matrix scan & debounce      | built-in interrupt support and debounce logic    |
-| Servo                 | SG90 control                 | official Arduino, simple API                   |
+| Servo               | SG90 control                | official Arduino, handles PWM timing internally  |
-=== Novelty Element ===
+=== Novelty & Lab Integration ===
-  * Time-lock feature enforcing business hours
+  * **PWM servo control** (Lab 3 – Timers/PWM): SG90 latch driven at 50 Hz; non-blocking auto-relock with `millis()`.
-  * Unlock log on LCD
+  * **Supply-voltage monitor** (Lab 4 – ADC): reads the 1.1 V band-gap on channel 14 every 5 s, prints VCC on Serial Monitor, blinks red LED when VCC < 4.6 V.
-  * Integration of multiple lab modules into one device
+  * **Shared I²C bus** (Lab 6 – I²C): DS1307 RTC and PCF8574 LCD expander operate on the same SDA/SCL lines.
-=== Development ===
+=== Architecture ===
-  * Arduino IDE / PlatformIO
+. **updateDisplay()**
+   - called once per second (via `millis()`), updates HH:MM:SS, renders PIN asterisks or “Last HH:MM”
+   - never blocks, so UI remains responsive
+. **handleKey()**
+   - ‘C’ clears entry, digits append to buffer (with asterisks), ‘D’ validates PIN
+   - on correct PIN, calls `unlockDoor()`; on wrong, increments counter or triggers alarm
+. **unlockDoor()**
+   - moves servo to unlock angle, lights green LED + buzzer for 1 s
+   - sets `lockRestoreMs = millis() + 5000` for non-blocking relock in `loop()`
+   - logs timestamp in `lastUnlock` for display
+. **loop()**
+   - checks `millis()` vs. `lockRestoreMs` to relock servo without pausing
+   - updates display every second and polls keypad
+   - validated by toggling between allowed/outside hours and using a stopwatch for timing
-=== Core modules ===
+=== Calibration & Optimizations ===
-  * `updateDisplay()`: live clock, PIN prompt/asterisks, last-unlock
+  * **Keypad debounce** is handled inside the Keypad library (no Timer2 code needed).
-  * `handleKey()`: ‘C’ clear, digit entry, ‘D’ submit with window check
+  * **Servo angles**: adjusted to 20° (unlock) and 110° (lock) for mechanical reliability.
-  * `unlockDoor()`: unlock sequence + schedule non-blocking relock
+  * **Blocking calls minimized**: only a 1 s buzzer delay remains; all longer waits use non-blocking `millis()` logic.
-=== Libraries ===
-  * Wire/RTClib
-  * LiquidCrystal_I2C
-  * Keypad
-  * Servo
-==== Safety & Build Quality ====
-- neat wiring on breadboard
-- LEDs have 330 Ω current-limiting resistors
 ==== Conclusions ====
-eSafe demonstrates integration of GPIO, interrupts, timers, PWM, and I²C into a user-friendly digital safe. Non-blocking design ensures smooth UI and reliable timekeeping.
+eSafe showcases the seamless integration of three core microcontroller features: PWM (servo latch), ADC (live VCC monitoring), and I²C (RTC + LCD). All time-sensitive tasks are handled with non-blocking `millis()` logic, so the user interface stays responsive while the clock remains accurate.
 ==== Bibliography & Resources ====
   * ATmega328P Datasheet