OpenWater Hub: An open-source hardware platform for marine robotics support and water quality data acquisition

At present, there is no single open-source electronic hardware platform that natively integrates 24 V industrial RS485 sensors with marine robotic and hydroponic actuation. Consequently, hardware fragmentation exists severely in underwater sensing and environmental monitoring. Researchers using benchtop calibration must purchase closed-source ecosystems with proprietary operating systems, limiting the use of custom control loops. Conversely, open-source embedded systems provide optimized low-voltage passive monitoring but lack sufficient power for heavy actuators. The OpenWater Hub (OWH) provides a centralized platform for these two areas to exist on one printed circuit board (PCB). The PCB features a 24 V pass-through bus that supports the heavy inrush currents of industrial RS-485 probes. A dual-ATmega128A topology is utilized to prevent serial polling delays from disrupting real-time motor control. The architecture consists of one chip that isolates Modbus communication for sub-millisecond parsing, and another chip that drives soft robotic fish and actuators via four 3.0 A PWM channels. The core board is configured to transform across four deployment variants: a benchtop logger, a portable field laboratory, an autonomous floating station, and a tethered robotic support hub. Modular UART sockets support telemetry via LoRa, Wi-Fi, Bluetooth, and cellular modules. The static baseline power consumption was 196.4 mW; after 240 h of thermal testing, the OpenWater Hub demonstrated $>99.97\text{\%}$ telemetry reliability and logged chemical validations yielding a 0.9903 correlation coefficient value. Documentation and C++ logic files for the reproduction of all deployment variants are included.