Most Raspberry Pi builds that need analog input, extra GPIO, and industrial serial end up with a stack of individual HATs. The CirkitScape Top HAT consolidates all of that onto a single board in the standard 7.62 x 5.08 cm (3 x 2 inch) HAT form factor. It pairs an MCP23017 I2C expander for 16 additional GPIOs with an ADS1015 12-bit ADC providing three analog channels and a MAX485 half-duplex RS-485 transceiver, then throws in a four-port USB 2.0 hub with per-port 500 mA current limiting. The board fits any 40-pin Pi from the Zero through the Pi 5.
On the software side, no custom firmware or kernel modules are involved. The Top HAT runs entirely over I2C, UART, and standard GPIO on Raspberry Pi OS, using familiar Python libraries: smbus2 for I2C, gpiozero for digital I/O, and pyserial for RS-485 communication. CirkitScape provides a setup script that enables the necessary interfaces, installs dependencies including adafruit-circuitpython-ads1x15 for the ADC, and creates a Python virtual environment. A bundled Flask-based web dashboard lets users toggle GPIOs, read ADC values, and interact with the RS-485 bus from a browser at port 5000, useful for quick hardware validation without writing any code.
The RS-485 interface includes an onboard 120-ohm termination resistor, a detail that matters for anyone connecting the Pi to Modbus devices or other industrial serial networks. Python Modbus libraries such as pymodbus pair naturally with the interface for Modbus RTU applications, covering use cases like reading from industrial sensors, PLCs, or multi-drop data loggers over a shared RS-485 bus. Combined with the three ADC channels and the GPIO expander, the Top HAT covers most of the I/O requirements for sensor data acquisition, IoT gateways, and embedded prototyping without occupying more than one HAT slot. The USB hub does require a separate USB cable connection to the Pi for the extra ports to function.
The Top HAT is available now for $45 (€41) from CirkitScape's website. A sensor kit bundling the board with temperature/humidity, soil moisture, and rain detection sensors is listed at $73 (€67), though its actual availability is unclear. CirkitScape is a small operation based in Alabama.
