# RTC PCF8523 Fallback Implementation Plan

> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.

**Goal:** Add a new header `src/rtcsync.h` that uses an Adafruit Adalogger FeatherWing (PCF8523) as persistent time storage and as a fallback time source when NTP is unavailable, while remaining fully optional (soft-fail without hardware).

**Architecture:** Header-only module following the existing AquaMaster pattern. Decoupled from `timesync.h` via GCC weak symbols, so devices without RTC compile and run unchanged. Time is stored in the RTC as UTC (POSIX epoch). NTP remains the authoritative source; RTC is consulted only at boot before WiFi comes up. Manual time sets (e.g. browser-time button) are persisted to RTC with a plausibility check.

**Tech Stack:** ESP32 / Arduino-Framework / PlatformIO, `adafruit/RTClib`, `ArduinoJson@^7.4.1`, existing `timesync.h` API.

**Spec:** [docs/superpowers/specs/2026-05-03-rtc-pcf8523-fallback-design.md](../specs/2026-05-03-rtc-pcf8523-fallback-design.md)

**Verification model:** This project has no unit-test suite (`test/` is empty). "Tests" in this plan mean: (1) build success across all PlatformIO envs, (2) serial-log behavior on real hardware, (3) HTTP-API checks via `curl`/browser. Each task ends with a verification step appropriate for the change.

---

## File Structure

| File | Role |
|------|------|
| `src/rtcsync.h` | **NEW** — header-only RTC module (globals + `setupRTC`, `loopRTC`, `syncFromNTP`, `persistSystemTimeToRTC`, weak-hook overrides) |
| `src/timesync.h` | Add two weak-symbol declarations + invocations (no behavioral change without `rtcsync.h`) |
| `src/master.cpp` | Include `rtcsync.h`; call `setupRTC()` before `setupWifi()`; call `loopRTC()` at start of `loop()` |
| `platformio.ini` | Add `adafruit/RTClib` to `lib_deps` of every env |

---

## Task 1: Add RTClib dependency to all PlatformIO envs

**Files:**
- Modify: `platformio.ini` (lines 30, 50, 70, 87, 105, 129 — `lib_deps` blocks of all six envs)

- [ ] **Step 1: Add `adafruit/RTClib@^2.1.4` to every `lib_deps` block**

In `platformio.ini`, append the line `	adafruit/RTClib@^2.1.4` (tab-indented like the other entries) to each of the six `lib_deps` sections. Concretely, each block should become:

```ini
lib_deps = 
	bblanchon/ArduinoJson@^7.4.1
	esp32async/ESPAsyncWebServer@^3.7.7
	esp32async/AsyncTCP@^3.4.2
	mlesniew/PicoMQTT@^1.3.0
	adafruit/Adafruit PN532@^1.3.4
	adafruit/RTClib@^2.1.4
```

Apply this edit to envs: `wemos_d1_mini32`, `esp32thing_OTA`, `esp32thing`, `esp32thing_CI`, `um_feathers3`, `um_feathers3_debug`.

- [ ] **Step 2: Verify CI env builds with new dependency**

Run: `pio run -e esp32thing_CI`
Expected: Library is downloaded (look for `Library Manager: Installing adafruit/RTClib`), build succeeds with `SUCCESS` line. No code change yet, so binary size should be essentially unchanged.

- [ ] **Step 3: Commit**

```bash
git add platformio.ini
git commit -m "build: add RTClib dependency for PCF8523 RTC support"
```

---

## Task 2: Create `src/rtcsync.h` skeleton with RTC detection (soft-fail)

**Files:**
- Create: `src/rtcsync.h`

- [ ] **Step 1: Create the skeleton file**

Create `src/rtcsync.h` with the following content. This is the smallest possible vertical slice — only detection, no time-handling yet:

```cpp
// PCF8523-RTC-Modul mit NTP-Sync und Fallback.
// Header-only nach Projekt-Pattern: Globale Objekte werden hier definiert.
// Dieser Header darf NUR in master.cpp inkludiert werden.
#pragma once
#include <Arduino.h>
#include <RTClib.h>
#include <Wire.h>

// Globale RTC-Instanz und Status-Flags
RTC_PCF8523 rtc;
bool rtcAvailable = false;
bool ntpEverSynced = false;
time_t lastNtpSyncEpoch = 0;
bool lastStaConnected = false;

// I2C-Init und PCF8523-Detektion. Soft-Fail: setzt nur rtcAvailable.
void setupRTC() {
  Wire.begin(); // idempotent — falls bereits durch andere Module aufgerufen
  if (!rtc.begin()) {
    Serial.println("[RTC] PCF8523 nicht gefunden — RTC-Funktionen deaktiviert");
    rtcAvailable = false;
    return;
  }
  if (!rtc.initialized() || rtc.lostPower()) {
    Serial.println("[RTC] PCF8523 erkannt, aber Akku-Backup ungültig (lostPower)");
    // Wir betrachten den Chip trotzdem als verfügbar — NTP wird ihn gleich neu setzen.
  }
  rtc.start(); // STOP-Bit löschen, falls gesetzt
  rtcAvailable = true;
  Serial.println("[RTC] PCF8523 initialisiert");
}
```

- [ ] **Step 2: Build CI env to verify the header compiles standalone**

The header is not yet included anywhere, so this only checks that the includes resolve. Run: `pio run -e esp32thing_CI`
Expected: `SUCCESS`, no warnings about `rtcsync.h`.

- [ ] **Step 3: Commit**

```bash
git add src/rtcsync.h
git commit -m "feat(rtc): add rtcsync.h skeleton with PCF8523 detection"
```

---

## Task 3: Add RTC → system-time fallback inside `setupRTC()`

**Files:**
- Modify: `src/rtcsync.h` (the `setupRTC()` function from Task 2)

- [ ] **Step 1: Extend `setupRTC()` to seed the system clock from RTC if available**

Replace the body of `setupRTC()` with:

```cpp
void setupRTC() {
  Wire.begin();
  if (!rtc.begin()) {
    Serial.println("[RTC] PCF8523 nicht gefunden — RTC-Funktionen deaktiviert");
    rtcAvailable = false;
    return;
  }
  if (!rtc.initialized() || rtc.lostPower()) {
    Serial.println("[RTC] PCF8523 erkannt, aber Akku-Backup ungültig (lostPower)");
  }
  rtc.start();
  rtcAvailable = true;
  Serial.println("[RTC] PCF8523 initialisiert");

  // Systemzeit aus RTC vorbelegen — wird ggf. später durch NTP übersteuert.
  // RTC speichert UTC, settimeofday erwartet UTC. Kein Offset nötig.
  DateTime nowRtc = rtc.now();
  uint32_t rtcEpoch = nowRtc.unixtime();
  // Plausibilität: RTC sollte mindestens 2025 zeigen, sonst ist sie ungestellt.
  if (rtcEpoch >= 1735689600UL) {
    struct timeval tv;
    tv.tv_sec  = (time_t)rtcEpoch;
    tv.tv_usec = 0;
    settimeofday(&tv, NULL);
    Serial.printf("[RTC] Systemzeit aus RTC gesetzt: %lu (UTC)\n",
                  (unsigned long)rtcEpoch);
  } else {
    Serial.printf("[RTC] RTC-Zeit unplausibel (%lu) — nicht übernommen\n",
                  (unsigned long)rtcEpoch);
  }
}
```

- [ ] **Step 2: Build CI env**

Run: `pio run -e esp32thing_CI`
Expected: `SUCCESS`. The header still isn't wired into `master.cpp`, so no runtime effect yet.

- [ ] **Step 3: Commit**

```bash
git add src/rtcsync.h
git commit -m "feat(rtc): seed system time from RTC at boot"
```

---

## Task 4: Add weak-symbol hooks to `timesync.h`

These hooks let `rtcsync.h` extend `timesync.h` without `timesync.h` knowing about it. Without `rtcsync.h` linked in, the weak default is a null pointer and the call sites short-circuit.

**Files:**
- Modify: `src/timesync.h:23-46` (`getCurrentTimeJSON`)
- Modify: `src/timesync.h:72-84` (`setSystemTime`)

- [ ] **Step 1: Add weak hook declarations near the top of `timesync.h`**

Insert these declarations directly after the existing `bool isValidDateTime(...)` line is declared (i.e. after the prototypes block, before `getCurrentTimeJSON`'s implementation around line 22). If no clean location exists, place them right after the `#include <time.h>` line:

```cpp
// Weak hooks — falls rtcsync.h kompiliert/gelinkt wird, überschreibt es diese.
// Ohne rtcsync.h sind beide Symbole nullptr und werden nicht aufgerufen.
extern "C" void onSystemTimeSet(time_t t) __attribute__((weak));
extern "C" void appendTimeStatus(JsonDocument &doc) __attribute__((weak));
```

- [ ] **Step 2: Convert `getCurrentTimeJSON()` doc type and invoke `appendTimeStatus`**

The existing function uses the deprecated `StaticJsonDocument<200>`. ArduinoJson v7 prefers plain `JsonDocument`. Replace lines 23–46 of `src/timesync.h` (the entire `getCurrentTimeJSON()` body) with:

```cpp
String getCurrentTimeJSON() {
  gettimeofday(&tv, &tz);
  now = tv.tv_sec;

  JsonDocument doc;
  doc["timestamp"] = (long)now;
  doc["success"] = true;

  // Zusätzliche Zeitinformationen
  gmtime_r(&now, &timeinfo);
  char timeStr[64];
  strftime(timeStr, sizeof(timeStr), "%Y-%m-%d %H:%M:%S", &timeinfo);
  doc["formatted"] = String(timeStr);
  doc["year"]   = timeinfo.tm_year + 1900;
  doc["month"]  = timeinfo.tm_mon + 1;
  doc["day"]    = timeinfo.tm_mday;
  doc["hour"]   = timeinfo.tm_hour;
  doc["minute"] = timeinfo.tm_min;
  doc["second"] = timeinfo.tm_sec;

  // Optionale RTC/Sync-Status-Felder, falls rtcsync.h gelinkt ist
  if (appendTimeStatus) {
    appendTimeStatus(doc);
  }

  String response;
  serializeJson(doc, response);
  return response;
}
```

- [ ] **Step 3: Invoke `onSystemTimeSet` from `setSystemTime()`**

Replace lines 72–84 of `src/timesync.h` (the `setSystemTime` function) with:

```cpp
bool setSystemTime(long timestamp) {
  struct timeval tv;
  tv.tv_sec = timestamp;
  tv.tv_usec = 0;

  if (settimeofday(&tv, NULL) == 0) {
    Serial.println("Zeit erfolgreich gesetzt: " + String(timestamp));
    if (onSystemTimeSet) {
      onSystemTimeSet((time_t)timestamp);
    }
    return true;
  } else {
    Serial.println("Fehler beim Setzen der Zeit");
    return false;
  }
}
```

- [ ] **Step 4: Build CI env to verify backwards compatibility**

`rtcsync.h` is still not included in `master.cpp`, so both weak symbols must resolve to nullptr and the `if (...)` guards must skip them.
Run: `pio run -e esp32thing_CI`
Expected: `SUCCESS`. No new warnings. Behavior is identical to before this commit (the hooks are no-ops).

- [ ] **Step 5: Commit**

```bash
git add src/timesync.h
git commit -m "feat(timesync): add weak hooks for RTC integration"
```

---

## Task 5: Implement `persistSystemTimeToRTC()` and the `onSystemTimeSet` override

**Files:**
- Modify: `src/rtcsync.h` (append below `setupRTC`)

- [ ] **Step 1: Append the persistence function and the weak-hook override**

Add the following at the end of `src/rtcsync.h`:

```cpp
// Plausibilitäts-Grenzen: 2025-01-01 .. 2100-01-01 (UTC).
// Verhindert, dass kaputte Timestamps (0, negativ, 1970) die RTC korrumpieren.
static constexpr uint32_t RTC_MIN_EPOCH = 1735689600UL; // 2025-01-01 00:00:00 UTC
static constexpr uint32_t RTC_MAX_EPOCH = 4102444800UL; // 2100-01-01 00:00:00 UTC

void persistSystemTimeToRTC(time_t t) {
  if (!rtcAvailable) return;
  if ((uint32_t)t < RTC_MIN_EPOCH || (uint32_t)t >= RTC_MAX_EPOCH) {
    Serial.printf("[RTC] persist abgelehnt — Timestamp unplausibel: %ld\n",
                  (long)t);
    return;
  }
  rtc.adjust(DateTime((uint32_t)t));
  Serial.printf("[RTC] in RTC geschrieben: %ld (UTC)\n", (long)t);
}

// Weak-Hook-Override aus timesync.h — wird automatisch aufgerufen,
// sobald irgendwo setSystemTime() Erfolg meldet.
extern "C" void onSystemTimeSet(time_t t) {
  persistSystemTimeToRTC(t);
}
```

- [ ] **Step 2: Build CI env**

Run: `pio run -e esp32thing_CI`
Expected: `SUCCESS`. Still no behavioral change because `rtcsync.h` is not yet included by `master.cpp`.

- [ ] **Step 3: Commit**

```bash
git add src/rtcsync.h
git commit -m "feat(rtc): persist system time to RTC with plausibility check"
```

---

## Task 6: Implement `syncFromNTP()` wrapper

**Files:**
- Modify: `src/rtcsync.h` (append at end)

- [ ] **Step 1: Add a thin wrapper around `syncTimeWithNTP()` from `timesync.h`**

`syncTimeWithNTP()` in `timesync.h:48` already does the NTP heavy lifting (configTime + 5 s polling loop) and prints success/failure. We just need to detect success after the fact (system clock is now > 2025) and persist + bookkeep.

Append to `src/rtcsync.h`:

```cpp
// Versucht NTP-Sync via timesync.h. Bei Erfolg: schreibt UTC in RTC,
// setzt ntpEverSynced=true, aktualisiert lastNtpSyncEpoch.
// Returns true bei Erfolg.
bool syncFromNTP() {
  // Snapshot vor dem Sync — wenn die Zeit hinterher >= 2025 und neuer als vorher,
  // werten wir den Sync als erfolgreich.
  time_t before = time(NULL);
  syncTimeWithNTP(); // benutzt Defaults aus timesync.h: pool.ntp.org, +1h, kein DST
  time_t after = time(NULL);

  bool ok = ((uint32_t)after >= RTC_MIN_EPOCH) && (after >= before);
  if (!ok) {
    Serial.println("[RTC] NTP-Sync fehlgeschlagen — RTC unverändert");
    return false;
  }

  // setSystemTime() wird intern von syncTimeWithNTP NICHT aufgerufen,
  // also den Weak-Hook-Pfad hier umgehen und direkt schreiben.
  persistSystemTimeToRTC(after);
  ntpEverSynced = true;
  lastNtpSyncEpoch = after;
  return true;
}
```

- [ ] **Step 2: Build CI env**

Run: `pio run -e esp32thing_CI`
Expected: `SUCCESS`.

- [ ] **Step 3: Commit**

```bash
git add src/rtcsync.h
git commit -m "feat(rtc): add syncFromNTP wrapper that persists to RTC"
```

---

## Task 7: Implement `loopRTC()` (STA reconnect edge + 24 h periodic)

**Files:**
- Modify: `src/rtcsync.h` (append at end)

- [ ] **Step 1: Add the loop-tick function**

Append to `src/rtcsync.h`:

```cpp
// Aus loop() aufgerufen. Triggert syncFromNTP():
//  - bei steigender Flanke von WiFi.isConnected() (STA-Reconnect)
//  - alle 24h, sobald STA verbunden ist
// Reine Vergleichsoperationen, NTP-Roundtrip selbst ist blockierend (~ms..5s).
void loopRTC() {
  bool sta = (WiFi.status() == WL_CONNECTED);

  // Edge: false -> true (frischer STA-Connect)
  if (sta && !lastStaConnected) {
    Serial.println("[RTC] STA-Reconnect erkannt — NTP-Sync");
    syncFromNTP();
  }
  lastStaConnected = sta;

  // 24h-Periodik (nur wenn STA online)
  if (sta && ntpEverSynced) {
    time_t nowEpoch = time(NULL);
    if (nowEpoch - lastNtpSyncEpoch >= 86400) {
      Serial.println("[RTC] 24h-Periodik — NTP-Sync");
      syncFromNTP();
    }
  }
}
```

`WiFi.h` ist bereits indirekt durch andere Header (`wificlass.h` → `WiFi.h`) verfügbar; falls der Build hier ein Symbol nicht findet, oben im Header `#include <WiFi.h>` ergänzen.

- [ ] **Step 2: Build CI env**

Run: `pio run -e esp32thing_CI`
Expected: `SUCCESS`. Bei `'WiFi' was not declared`: `#include <WiFi.h>` ganz oben in `rtcsync.h` ergänzen und neu bauen.

- [ ] **Step 3: Commit**

```bash
git add src/rtcsync.h
git commit -m "feat(rtc): add loopRTC with STA-reconnect and 24h re-sync"
```

---

## Task 8: Implement `appendTimeStatus()` override

**Files:**
- Modify: `src/rtcsync.h` (append at end)

- [ ] **Step 1: Add the JSON-extension override**

Append to `src/rtcsync.h`:

```cpp
// Weak-Hook-Override aus timesync.h — erweitert /api/time um RTC-Status.
extern "C" void appendTimeStatus(JsonDocument &doc) {
  doc["rtc_available"] = rtcAvailable;
  doc["rtc_synced_from_ntp"] = ntpEverSynced;
  doc["last_ntp_sync_ago_s"] =
      ntpEverSynced ? (long)(time(NULL) - lastNtpSyncEpoch) : (long)-1;
  if (rtcAvailable) {
    doc["rtc_time_utc"] = (long)rtc.now().unixtime();
  } else {
    doc["rtc_time_utc"] = (long)0;
  }
}
```

- [ ] **Step 2: Build CI env**

Run: `pio run -e esp32thing_CI`
Expected: `SUCCESS`.

- [ ] **Step 3: Commit**

```bash
git add src/rtcsync.h
git commit -m "feat(rtc): expose RTC status fields via /api/time"
```

---

## Task 9: Wire `rtcsync.h` into `master.cpp`

This is the activation step. Until now, `rtcsync.h` exists but is unused. After this commit, devices with the FeatherWing get RTC behavior; devices without it print one warning line and run normally.

**Files:**
- Modify: `src/master.cpp:3-25` (include block) and `src/master.cpp:31-81` (setup/loop)

- [ ] **Step 1: Add the include**

In `src/master.cpp`, add `#include <rtcsync.h>` directly after the existing `#include <timesync.h>` line (currently line 23). The new include block tail should look like:

```cpp
#include <rfid.h>
#include <timesync.h>
#include <rtcsync.h>
#include <webserverrouter.h>
#include <wificlass.h>
```

**Reihenfolge:** `rtcsync.h` MUSS nach `timesync.h` kommen — die Weak-Hook-Overrides in `rtcsync.h` brauchen die Deklarationen aus `timesync.h`.

- [ ] **Step 2: Call `setupRTC()` before `setupWifi()`**

In `setup()`, insert `setupRTC();` directly before the existing `setupWifi();` call (currently line 53). The relevant block becomes:

```cpp
  loadWifiSettings();
  loadLocationSettings();

  setupRTC();  // RTC zuerst, damit Systemzeit vor WiFi plausibel ist
  setupWifi(); // WiFi initialisieren
  setupOTA(&server);
```

- [ ] **Step 3: Add an explicit NTP-sync attempt after WiFi is up**

After `setupWifi()`, the STA may already be connected. The first `loopRTC()` call would catch the edge eventually, but doing one explicit boot-time sync makes the boot log cleaner. Insert directly after `setupWifi();`:

```cpp
  setupWifi(); // WiFi initialisieren
  if (WiFi.status() == WL_CONNECTED) {
    syncFromNTP();
    lastStaConnected = true; // Edge bereits "konsumiert"
  }
  setupOTA(&server);
```

- [ ] **Step 4: Call `loopRTC()` at the start of `loop()`**

In `loop()` (currently lines 65–81), make `loopRTC()` the first call after `checkAutoReset()`:

```cpp
void loop() {
  checkAutoReset();
  loopRTC();

  // MQTT hat höchste Priorität (wird zuerst verarbeitet)
  loopMqttServer();
  ...
```

- [ ] **Step 5: Build all PlatformIO envs**

Run them sequentially (or in one go if your machine handles it):

```
pio run -e esp32thing_CI
pio run -e esp32thing
pio run -e wemos_d1_mini32
pio run -e um_feathers3
```

Expected: every env reports `SUCCESS`. Note the increase in flash usage (RTClib is small, ~5 KB).

- [ ] **Step 6: Commit**

```bash
git add src/master.cpp
git commit -m "feat(rtc): wire rtcsync into setup/loop"
```

---

## Task 10: Hardware verification on real device

This task is mandatory — automated tests cannot validate the I²C interaction or boot ordering. If no FeatherWing is currently attached, do at least Sub-step A (no-hardware soft-fail check).

**Files:** none (manual)

- [ ] **Step A — Without RTC attached: confirm soft-fail path**

1. Ensure no FeatherWing is plugged in.
2. `pio run -e esp32thing -t upload`
3. `pio device monitor -b 115200`
4. Expected serial output during boot:
   ```
   [RTC] PCF8523 nicht gefunden — RTC-Funktionen deaktiviert
   ```
   followed by the rest of the boot sequence reaching the WiFi/MQTT init **without crash or reboot loop**.
5. Open `http://<device-ip>/api/time` in the browser. Expected JSON contains:
   ```json
   "rtc_available": false,
   "rtc_synced_from_ntp": <true if STA is online, else false>,
   "rtc_time_utc": 0
   ```

- [ ] **Step B — With RTC attached, no NTP (AP-only mode)**

1. Plug in the Adalogger FeatherWing.
2. Disconnect the device from any STA network (factory-reset WiFi or boot in AP-only).
3. Boot, observe serial:
   ```
   [RTC] PCF8523 initialisiert
   [RTC] Systemzeit aus RTC gesetzt: <epoch> (UTC)
   ```
   (If the RTC was never set, the line says "unplausibel" instead — acceptable for a fresh chip.)
4. Connect to the AP and load `http://192.168.10.1/api/time`. Expected: `rtc_available: true`, formatted time matches the RTC's last known value.

- [ ] **Step C — With RTC attached, with NTP**

1. Configure WiFi-STA credentials so the device joins the home network.
2. Boot, observe serial:
   ```
   [RTC] PCF8523 initialisiert
   [RTC] Systemzeit aus RTC gesetzt: ...
   ... (WiFi connect)
   Warte auf NTP-Zeit (max 5s)...
   NTP-Zeit synchronisiert!
   [RTC] in RTC geschrieben: <epoch> (UTC)
   ```
3. `curl http://<device-ip>/api/time` — expected `rtc_synced_from_ntp: true`, `last_ntp_sync_ago_s` close to 0, `rtc_time_utc` matches `timestamp`.

- [ ] **Step D — Browser-time persistence**

1. With device booted (Step C), use the existing "set browser time" button in the settings UI.
2. Power-cycle the device with WiFi disabled (pull antenna or block STA).
3. Boot. Expected: serial shows the time from the browser-set, not 1970.

- [ ] **Step E — Document outcome**

If all steps pass: the task is done.
If any step fails: do **not** mark this task complete. Open a follow-up note describing what failed and which task's assumptions were wrong.

---

## Self-Review (already performed)

- **Spec coverage:** Each spec section maps to a task — Architecture/library → Task 1; new header + soft-fail → Tasks 2–3; weak-hook decoupling → Tasks 4–5; NTP-sync wrapper → Task 6; loop integration → Task 7; API extension → Task 8; setup/loop wiring → Task 9; hardware verification → Task 10.
- **Placeholder scan:** No TBD/TODO; all code blocks are concrete and copy-pasteable.
- **Type/name consistency:** `appendTimeStatus`, `onSystemTimeSet`, `persistSystemTimeToRTC`, `syncFromNTP`, `setupRTC`, `loopRTC`, `rtcAvailable`, `ntpEverSynced`, `lastNtpSyncEpoch`, `lastStaConnected`, `RTC_MIN_EPOCH`, `RTC_MAX_EPOCH` all used consistently across tasks.
- **Bounds check:** `RTC_MIN_EPOCH = 1735689600` (2025-01-01) and `RTC_MAX_EPOCH = 4102444800` (2100-01-01) — match the spec's "Year 2025–2099" range.