Build reliable Lua firmware for ESP8266 and ESP32 that ships, updates, and runs for months without fuss. Developers run into tight RAM, fragile Wi-Fi, and brittle updates when small devices meet real homes. This book gives you a practical workflow to choose the right ESP boards, keep heaps stable, and move code into flash so your nodes stay responsive. You will set up a lean toolchain, flash clean images, and structure Lua the way production devices need it, from sensor reads to secure messaging and Home Assistant integration. Pick ESP8266, ESP32 C3, S3, or C6 with clear RAM, flash, radio, and power tradeoffs Install Python tools, drivers, esptool, and a dependable serial console on any OS Build tight NodeMCU firmware, prune modules, and use LFS to keep code in flash Understand GC behavior, configure pause and step multipliers, and prevent heap spikes Use tmr, file, node, wifi, net, mqtt, tls, sjson for stable event driven code Choose SPIFFS or LittleFS wisely, migrate safely, and avoid wear issues Stage boot flow with init.lua, safe mode, and staged startup loaders Perform Lua OTA with HTTP pull, verify images, and implement clean rollback Configure Wi-Fi profiles with static IP and BSSID for fast reconnect after sleep Stream sockets and HTTP without big buffers, size TLS records, handle certs Design MQTT lifecycles with keepalive, LWT, retain strategy, and backoff Integrate with Home Assistant using MQTT Discovery topics and payload templates Wire DS18B20, BME280, SHT3x, relays, MOSFETs, and PWM dimmers with robust retries and safety Handle analog inputs on ESP chips, avoid reference pitfalls, and validate readings Plan deep sleep, wake sources, static IP, and BSSID cache for battery life Budget power, measure real current, and estimate device life with a simple script Secure traffic with TLS settings that fit in RAM, or apply PSK with rotation plans Use ESP32 OTA partitions and rollback flow for firmware updates that recover Provision unique credentials per device and expose a clear recovery mode Troubleshoot heap and GC under TLS and JSON load, prevent brownouts and boot loops Capture crashes and field logs, toggle safe mode with remote flags, and set guardrails Know when NodeMCU is not the right tool and what alternatives to pick Apply end to end tests from device to broker to Home Assistant dashboards Includes field ready case studies, a production checklist, security review steps, update playbooks, and rollback drills you can run on the bench before you ship. This is a code heavy guide with working Lua snippets, esptool commands, and MQTT payloads you can paste, adapt, and deploy to real devices. Grab your copy today.