ESP32 — Shelly Pro 3EM + Zendure SolarFlow Monitor & Watchdog

Budget ESP32-S3 port of gigar1-shelly-zendure-monitor — same features, ~1/3 the cost. Tested on hardware: 24 h+ stable over a full day/night cycle with the LovyanGFX display driver.

An independent, cloud-free monitor and safety watchdog for a home battery setup, running on an ESP32-S3 with an 800×480 display. It reads a Shelly Pro 3EM (grid meter) and a Zendure SolarFlow battery read-only over their local HTTP APIs, shows live data and a daily energy balance, raises a visible alarm on misbehaviour, and serves its own JSON API.

Live dashboard on the ELECROW 7″ panel: grid total, per-phase L1/L2/L3, Zendure SoC/output, daily energy balance.

This is the cheaper sibling of the Arduino GIGA R1 version — same features, ~1/3 the cost.

Hardware

• ELECROW 7″ HMI ESP32 Display, 800×480 RGB TFT — ESP32-S3-WROOM-1, 8MB PSRAM, RGB parallel panel (driver EK9716BD3), GT911 capacitive touch. ELECROW sells the same board under two names over time: "ESP32 Display / Wizee" and "CrowPanel ESP32 HMI 7.0". (The titles say "ESP32 / LX6" but it is an ESP32-S3.)
  • 800×480 — same resolution as the GIGA display, so the layout carries over 1:1
• Shelly Pro 3EM (3-phase grid meter, on the LAN)
• Zendure SolarFlow (e.g. 2400 / 2400 Pro, on the LAN via WiFi)
• Power: ~450 mA @ 5 V (~2.25 W) in operation — any USB port or a small 5 V charger (≥ 500 mA, 2.5–10 W) is plenty. No 20 W+ charger needed.

Libraries

• WiFi (ESP32 Arduino core) — native; WiFiClient / WiFiServer
• ArduinoJson (>= 7.x)
• LovyanGFX 1.2.24 — RGB parallel panel driver. Version pairing matters: use 1.2.x with core 2.0.17 (this release), or 1.1.12 with core 2.0.3 (previous release, see the v1.1.0 tag). 1.1.x won't compile on the newer core and 1.2.x won't compile on 2.0.3 — keep the pair matched. NOT TFT_eSPI — ELECROW confirms the 4.3″/5.0″/7.0″ HMI displays don't use it. No LVGL needed — LovyanGFX's Adafruit-GFX-style API matches the GIGA drawing helpers, so the monitor draws directly.
  • Why LovyanGFX, not Arduino_GFX? The first port used Arduino_GFX 1.2.8 and crashed every few hours: the RGB framebuffer DMA in PSRAM corrupted WiFi memory under normal load (PANIC / heap corruption). LovyanGFX's PSRAM/DMA management fixes it — identical sketch logic, 24 h+ stable.
• esp_task_wdt (ESP-IDF, built in) — hardware task watchdog (120 s)

Recommended toolchain (v2.0.0): core 2.0.17 + LovyanGFX 1.2.24 — validated on hardware (24 h+ stable, rode through a 12-min WiFi outage, daily balance preserved across reboot/power-cut). It brings ongoing WiFi/stability fixes and the newer IDF (4.4.2+, RGB bounce-buffer available) over the original 2.0.3. The earlier 2.0.3 + LovyanGFX 1.1.12 combo remains a working fallback at the v1.1.0 tag. Stay on a 2.0.x core — core 3.x changes APIs this sketch relies on.

ELECROW ships its own library bundle (LovyanGFX, Arduino_GFX, gt911-arduino touch, lvgl, …) and a factory test program for this panel:

• Libraries: https://www.elecrow.com/download/product/ESP32_Display/Arduino_Libraries.zip
• Setup tutorial (4.3″/5.0″/7.0″): https://www.youtube.com/watch?v=iKJesBu_cg4

RGB panels need correct timing (hsync/vsync/pclk/porches). This sketch uses the LovyanGFX config for the ELECROW 7″ panel (Sunton-8048S070 timing, PCLK=GPIO0, 8 MHz). If a different panel batch shows shift/stripes, adjust the porches / pclk_idle_high in the LGFX class.

Features (ported from the GIGA version)

• Live grid power: total + per phase L1/L2/L3 (W / V / A)
• Zendure status (read-only): SoC, output, acStatus — incl. "API hung / OFFLINE"
• Daily energy balance [kWh] since midnight (auto-reset)
• Watchdog/alarm: grid-dumping, deep discharge, BMS-critical (independent cell-V/temp check), debounced against device-reboot transients
• Device health (Shelly/Zendure: ok / hung / offline)
• Heartbeat + hardware watchdog (self-supervision), robust WiFi reconnect
• JSON API: /status, /balance (cell-balancing history), /daily (30-day diary)
• Own IP shown on the display
• Daily balance survives reboots & power loss (NVS) — see Persistence & resilience

Persistence & resilience (v1.1)

The daily energy balance is kept in NVS (the ESP32's non-volatile flash key-value store): on every reboot — including a real power cut — the board restores the day's baseline if the stored entry is from the same local day, so the saldo continues instead of resetting to zero. A fresh baseline is written only ~once per day (at the midnight rollover or the first start of a new day), so flash wear is negligible (~1 write/day). Validated on hardware across a 12-minute network outage and a cold power-cycle.

The /status API gained matching diagnostics:

Field	Meaning
base_restored	true if the day's saldo was restored from NVS after a reboot
boots	persistent boot counter — reveals unobserved reboots
min_free_heap	lowest free internal heap since boot (leak indicator)
rssi	current WiFi signal strength (dBm)

Optional: Control-Watch tile (local controller supervision)

If you also run the local zero-feed-in controller (a regler + MQTT broker on separate boards), this monitor can supervise it and show a small CONTROL OK (green) / … DOWN (red) tile in the top bar — a glanceable, always-on health light on independent, diverse hardware.

• Polls the controller's and broker's read-only /status every 20 s.
• Turns red — showing which side is silent (REGLER DOWN / BROKER DOWN / CONTROL DOWN) — after more than CONTROL_FAIL_N (3) consecutive misses (~80 s; set CONTROL_FAIL_N = 2 for ~60 s).
• Off by default. If you use the Zendure's own cloud/HEMS control (no local controller), leave it off so you never see a false red. When disabled, none of this code compiles — the monitor is byte-for-byte unchanged.

To enable: set #define CONTROL_WATCH_ENABLE 1 in the sketch and add the two IPs (SECRET_REGLER_HOST, SECRET_BROKER_HOST) to arduino_secrets.h (see the example file). Read-only, like everything else here. The tile state is also exposed in /status (ctrl_state, ctrl_fail_r, ctrl_fail_b).

Setup

1. Copy shelly_monitor_esp32/arduino_secrets.example.h → shelly_monitor_esp32/arduino_secrets.h
2. Fill in all four values: WiFi SSID/password + local IPs of the Shelly and Zendure. Give each device (and this board) a fixed IP (DHCP reservation) so addresses stay stable. (The two extra SECRET_REGLER_HOST / SECRET_BROKER_HOST entries are only needed if you enable the optional Control-Watch tile.)
3. Arduino IDE board settings (ELECROW, confirmed for the 7″ HMI display):
   • Boards Manager → install esp32 by Espressif, version 2.0.17 (URL: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json) — pair with LovyanGFX 1.2.24. (For the 2.0.3 + 1.1.12 fallback, see the v1.1.0 tag.)
   • Board: ESP32S3 Dev Module
   • PSRAM: OPI PSRAM · Flash Mode: QIO 80MHz
   • Flash Size: depends on the ESP32-S3-WROOM-1 variant on the shield — N16R8 → 16MB (the guide's default) or N4R8 → 4MB. PSRAM is 8MB either way. Check the metal-shield label; if upload fails with 16MB, try 4MB.
   • Partition Scheme: Huge APP (3MB No OTA/1MB SPIFFS)
   • CPU Frequency: 240MHz (WiFi) · Upload Speed: 921600
4. Upload: if the IDE can't enter download mode, hold BOOT, press RESET (serial shows waiting for download), then upload; press RESET to run.

arduino_secrets.h is git-ignored — credentials are never committed.

📋 Step-by-step flashing checklist: docs/FLASHING.md

⚠️ Disclaimer

Read-only monitor for display purposes, not a certified safety device. The real cell protection is the battery's own BMS. Use at your own risk.

License

MIT — Copyright (c) 2026 Reinhard Jesolowitz