Weathergotchi, an open-source climate Tamagotchi

An open-source hardware project called the E-Paper Climate Logger provides a battery-powered temperature and humidity data logger with an always-on e-paper display, according to project documentation. The device records ambient conditions over time, stores readings in non-volatile memory, and displays current data along with a history graph. It is designed for low power consumption, achieving over one week of operation on a small lithium-polymer battery. Key hardware includes an ESP32-S3 microcontroller with deep sleep and a real-time clock timer, a temperature and humidity sensor with external EEPROM for logging, accurate battery monitoring, a power button controller, and a 1.54-inch e-paper display. The project uses a custom printed circuit board and a 3D-printed case. The entire project is open source, including hardware schematics, PCB layout, firmware, and enclosure CAD files. A detailed build video is available on YouTube. The firmware is a PlatformIO project for the ESP32-S3 using the Arduino framework. It handles sensor reading, timekeeping, data logging to EEPROM, e-paper display updates, button handling, and power management. Known issues include inaccurate battery state-of-charge reporting, potential unrecoverable low-battery states, temperature reading skew from ESP32 heat during handling, and e-paper display limitations below freezing. The device does not include wireless connectivity to maximize battery life.