Standalone-electricity-price-ticker/CHANGELOG.md

Changelog

All notable changes to this project are documented here.

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v6.2.1 – Current Interval Fix (2026‑03‑29)

Summary

Fixed a bug where the display was showing prices one hour ahead of the current time.

Problem: Display Showing Next Hour Instead of Current

Root Cause:

The findCurrentPriceIndex() function was finding the next 15-minute interval (first entry with timestamp >= now), but it should find the current interval (the one we're currently IN).

For example, at 17:57:

• The current 15-minute interval is 17:45-18:00 (price indexed at 17:45)
• The next interval is 18:00-18:15 (price indexed at 18:00)
• The buggy function returned the index for 18:00 instead of 17:45
• Result: Display showed hour 18 instead of hour 17

Solution

The fix calculates the next 15-minute boundary and finds the last entry strictly before that boundary:

// Calculate the next 15-minute boundary
const int QUARTER_SECONDS = 15 * 60; // 900 seconds
time_t nextQuarter = ((now + QUARTER_SECONDS - 1) / QUARTER_SECONDS) * QUARTER_SECONDS;

// Find the last entry strictly before nextQuarter
for (size_t i = unixSeconds.size(); i > 0; i--) {
    if ((time_t)unixTime < nextQuarter) {
        return (int)(i - 1);
    }
}

Example:

• At 17:57: nextQuarter = 18:00, finds last entry < 18:00 = 17:45 ✅
• At 18:00: nextQuarter = 18:15, finds last entry < 18:15 = 18:00 ✅
• At 18:46: nextQuarter = 19:00, finds last entry < 19:00 = 18:45 ✅

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v6.2.0 – DST (Daylight Saving Time) Handling Fixed (2026‑03‑29)

Summary

This release fixes a critical bug that caused incorrect price display on DST switch days. On March 29, 2026 (the spring forward day), the ticker at 12:41 showed prices for hours 13:00, 14:00, and 15:00 instead of the correct 12:00, 13:00, and 14:00.

Problem: Arithmetic-Based Index Calculation

Root Cause (v6.0.0 – v6.1.2):

The code assumed every day has exactly 96 price entries:

int startIndex = hourIndex * 4;  // e.g., hour 12 → index 48

This assumption breaks on DST switch days:

Day Type	Hours	Price Entries	Example
Normal day	24	96	Array indices 0-95
Spring forward (March)	23	92	Index 48 points to wrong time
Fall back (October)	25	100	Index 48 points to wrong time

At 12:41 on March 29, 2026:

• ESP32 correctly reported timeinfo.tm_hour = 12
• Old code calculated 12 × 4 = 48
• But array only had 92 entries (no index 48 that maps to local hour 12)
• Result: Displayed prices for 13:00, 14:00, 15:00 instead of 12:00, 13:00, 14:00

Solution: Timestamp-Based Lookups

New approach (v6.2.0):

All price lookups now search the unix_seconds array using actual timestamps:

// Find index by searching for matching hour in timestamps
int findPriceIndexForHour(const JsonArray& unixSeconds, int targetHour) {
    for (size_t i = 0; i < unixSeconds.size(); i++) {
        unsigned long unixTime = unixSeconds[i].as<unsigned long>();
        time_t t = (time_t)unixTime;
        struct tm* ptm = localtime(&t);
        if (ptm != NULL && ptm->tm_hour == targetHour) {
            return (int)i;  // Found correct index for this hour
        }
    }
    return -1;
}

New functions added:

• findPriceIndexForHour() – Finds first price index for a given hour
• findCurrentPriceIndex() – Finds current 15-minute slot using Unix timestamp
• getHourFromPriceIndex() – Gets hour from price array index

Updated functions:

• getHourlyAverage() – Now uses timestamp lookup instead of hourIndex * 4
• display15MinuteDetails() – Timestamp-based with hour verification in loop
• displayPriceRow() – Timestamp-based data index lookup
• displayPrimaryList() – Timestamp-based current hour detection
• updateLeds() – Timestamp-based current interval lookup

Why This Is Future-Proof

Scenario	Code Behavior
Normal days (96 entries)	Works as before
DST spring forward (92 entries)	Timestamp lookup finds correct indices
DST fall back (100 entries)	Timestamp lookup finds correct indices
EU cancels DST	Only update TZ_CET_CEST string; code works unchanged

If EU parliament ever cancels DST switching, you only need to update the TZ_CET_CEST line (one line of code). The price lookup logic requires no changes.

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v6.1.2 – LED Indicator Restored (ESP32 PWM Fix) (2026‑03‑11)

Summary

This release fixes a regression introduced in v6.1.1 where the white LED price indicator could remain dimly lit even when the LCD backlight turned off, and the intended blink/breathe patterns no longer behaved correctly.

Fixed: White LED Stuck Dim / Patterns Broken (PWM vs Digital)

Problem (v6.1.1):

• The sketch uses analogWrite() to drive the LED with PWM for breathe/blink patterns.
• However, in some "LED OFF" branches the code used digitalWrite(LOW) on the same whiteLedPin.
• On ESP32 (LEDC), once PWM is attached to a pin, digitalWrite(LOW) may not fully disable PWM output.
• Result:
  • LED could remain faintly on (dim glow) when LEDs were supposed to be off.
  • Some patterns could appear "stuck" or inconsistent.

Solution (v6.1.2):

• LED control is now PWM‑only inside updateLeds():
  • Use analogWrite(whiteLedPin, 0) instead of digitalWrite(whiteLedPin, LOW).
  • Use analogWrite(whiteLedPin, 255) instead of digitalWrite(whiteLedPin, HIGH).
  • Blink/double‑blink toggles now switch between PWM 0 and 255.
• This ensures the LED is truly off whenever LED output is gated off.

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v6.1.1 – Daily Min/Max Includes Negative & Zero Prices (2026‑03‑07)

Summary

This release fixes a bug where the daily lowest / highest hourly price marker ignored negative prices (and also ignored 0.0), which could cause the ticker to incorrectly mark the lowest positive price as the daily minimum.

Fixed: Daily Low/High Marker Ignored Negative & Zero Prices

Problem (v6.1.0):

• In processJsonData() the daily min/max scan used:

  if (hourlyAvg > 0) { ... }
  

• This had two side effects:
  1. Negative hourly averages were completely skipped.
  2. A true price of 0.0 was also skipped (even though 0 can be a valid market price).

Solution (v6.1.1):

• The min/max and average scan now:
  • Treats an hour as valid based on data availability (having all 4×15‑minute entries), not based on value sign.
  • Includes all values (negative, zero, positive).

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v6.1.0 – Midnight Fetch & Market Day Fix (2026‑01‑30)

Summary

This release fixes a bug where the ticker could remain indefinitely on the "No data for today" screen after midnight, even though the API was already returning fresh data.

Fixed: Stuck on NO_DATA_OFFSET After Midnight

Problem (v6.0.0):

• The API can continue to serve yesterday's market day for some time after local midnight.
• HTTP + JSON success always incremented apiSuccessCount, even if the data was "not for today".
• The scheduler treated such fetches as successful and never retried.

Solution (v6.1.0):

• processJsonData() now determines the "market day" using the last unix_seconds timestamp.
• A scheduled fetch is only successful if lastProcessJsonAcceptedToday == true.
• Midnight retry logic keeps trying until valid "today" data is received.

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v6.0.0 – NVS Storage & Daily Fetch (2026‑01‑27)

Summary

First major redesign focused on reducing API traffic and improving resilience using non‑volatile storage.

New

• NVS namespace "my-ticker" with Wi‑Fi credentials and daily price data caching.
• Boot behavior: Try to load and validate NVS data; if date matches today → reuse it and skip initial API call.
• After‑midnight: NVS is overwritten with each successful new‑day dataset.

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v5.x – Earlier Versions

Earlier versions (v5.x and below) had:

• No NVS‑based caching of daily API data.
• More frequent API calls (e.g., hourly refresh pattern).
• Less robust handling of DST and daily boundaries.

For exact details, see older .ino files and their header comments in this repository.