The SenTiBoard is a sensor timing board that accurately records when sensor messages are validated. To achieve high accuracy the SenTiBoard uses a 200 MHz microcontroller with a 100 MHz 32-bit internal clock, resulting in a resolution of 10 ns. The board uses the microcontroller's interrupt capture functionality, which registers the timestamp when a flank on a pin is detected, to register a sensor's reported Time of Validity (TOV) or Pulse Per Second (PPS). In addition, the time the first byte is transferred is also recorded, to support sensors that do not have dedicated TOV signals.
Primarily, the SenTiBoard both communicates and is configured through the USB interface. This allows the board to be configured and tested on a standard computer on the operative system of choice, and then transferred to the on-board payload computer. If USB is not present on the on-board computer, other interfaces such as SPI or UART can be used, and sensor logging directly to an SD-card is planned. The SenTiBoard is designed to fit on top of the ODroid XU4 single board computer, with dimensions of 83 mm x 59 mm. To reduce the size further, the legs can be broken off, resulting in a board of 60 mm x 50 mm.
To provide a quick and easy solution for accurate navigation, the SenTiStack consists of a compact setup with a set of sensors, providing synchronized RTK GNSS measurements and with INS data. The SenTiStack is built up of a SenTiBoard, a uBlox GNSS receiver, one or more tactical grade IMUs - typically an ADIS164XX and/or a STIM300, and an onboard computer. We are working on integrating a magnetometer and a uBlox receiver in a more convenient and compact package for the SenTiStack.
In addition to the pure hardware solutions, the SenTiStack aims to provide documentation and a well-tested software framework for logging data, configuring sensors, parsing sensor messages, and converting the sensor information to higher-level formats, such as MATLAB and the Python's NumPy implementation.