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[GUIDE] Sniffing & Debugging WiFi Plug Pro (SmartESS/Easun) with Arduino/ESP32 Hi all, I struggled for hours trying to recover and debug a “WiFi Plug Pro” data logger (the typical dongle used for SmartESS/Easun/Sunsynk app), after it got “orphaned” due to a WiFi change and was not visible in the app. Long story short: If you want to analyze or reset one of these dongles, skip all the Home Assistant/ESPHome drama and go straight to Arduino or ESP32 with serial. Here’s how:What You NeedESP32 development board (any model, I used a generic ESP32-WROOM-32) Arduino IDE (or PlatformIO, but Arduino IDE is quick and easy) Jumper wires Optionally: A USB-TTL adapter (not strictly needed if you have an ESP32) The WiFi Plug Pro dongle (with exposed debug pins or RX/TX pads, see photos below) https://imgur.com/a/wSgpjd1 Wiring (ESP32 as Serial Sniffer)Find the debug/serial pads on your WiFi dongle. In my unit, there were two rows of pads—one was regular UART for the inverter (usually 9600 baud), the other was an internal debug UART (115200 baud). Connect ESP32 GND to dongle GND Connect ESP32 RX (GPIO16) to the dongle’s TX pin (from the debug/UART pads). You don’t need to connect ESP32 TX (unless you want to send commands, for simple sniffing just RX is fine). Power: Either power the dongle from its own USB (recommended) or, if you know what you’re doing, from ESP32 3.3V pin (if the dongle accepts it—check specs first). Code (Arduino IDE Example)void setup() { Serial.begin(115200); // Monitor serie a 9600 Serial2.begin(9600, SERIAL_8N1, 16, 17); // RX=16 } void loop() { while (Serial2.available()) { char c = Serial2.read(); Serial.write(c); } } Open Serial Monitor in Arduino IDE at the correct baud rate (115200 for debug logs, 9600 for inverter communication). You’ll see boot logs, debug info, and even WiFi status messages. Findings & ObservationsThe debug UART on the WiFi Plug Pro logs everything: Boot process, WiFi attempts, errors, Modbus communication, even the current SSID and password in plaintext (be careful!). If you changed the WiFi and lost access to the dongle: This method lets you recover/see what SSID and password it’s looking for, or reset/reconfigure the dongle via serial. You’ll see lines like: board_wifi_connect_reinit: sta_ssid_str= TP-LINK_Sim, wifi_sta_sskey = 23062023That’s the SSID and password it’s expecting! You’ll also see Modbus RTU traffic and cloud connection attempts. ConclusionIf your logger is “bricked”, “lost”, or can’t reconnect to the app, this serial debug trick is a lifesaver. Don’t waste time on ESPHome or fancy integrations just to sniff/debug—Arduino/ESP32 with serial monitor is the fastest route. If anyone needs extra help with this or wants to automate recovery/reset, reply here and I’ll try to help. Hope this helps someone—thanks to all in this thread for the inspiration!