Tech Briefs

Dual I²C and SPI Slave Core for FPGA and ASIC Implementations

Goddard Space Flight Center, Greenbelt, Maryland The I2C/SPI Verilog core consists of a combined register transfer logic (RTL) Verilog code for a general-purpose I2C and serial-to-parallel interface (SPI) slave for implementations targeting field programmable gate arrays (FPGAs) and application specific integrated circuits (ASICs). The core was developed as part of the radiation hardened digital-to-analog converters’ 10-bit (RH-DAC10) and 12-bit (RH-DAC12) ASICs. The core contains both an I2C and SPI slave cores that share all inputs/outputs, and is selectable by setting a single input. The I2C portion uses an asynchronous design and does not require a continuous clock to operate, thus reducing the dynamic power consumption. The core serves as a baseline that can be tailored to any application requiring I2C and SPI slave interfaces. The core has been implemented and verified in both a commercial FPGA and a custom, radiation-hardened ASIC in a commercial CMOS (complementary metal-oxide semiconductor) 0.25-μm process, where the I2C and SPI were tested at 1 MHz and 50 MHz, respectively.

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Automated Break-Out Box for Use with Low-Cost Spacecraft Integration and Test

Goddard Space Flight Center, Greenbelt, Maryland Electrical checkout and testing is a critical part of the overall space integration and test flow. Verifying proper harness and connector signal interfaces is key to ensuring component health and overall system functionality. Break-out boxes (BOBs) are used to give test personnel access to electrical signals for probing, voltage injection, isolation checks, safe-to-mate checks, and voltage/current measurements, and comparing to expected results. Currently, this involves manually attaching multimeters and oscilloscopes to banana jacks on the BOB, taking measurements, and comparing to expected results.

Posted in: Briefs, TSP, Electronic Components

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Radiation-Hardened 10BASE-T Ethernet Physical Interface (PHY)

Goddard Space Flight Center, Greenbelt, Maryland The EXPRESS Logistics Carrier (ELC) system was built by NASA Goddard for installation on the International Space Station (ISS). Four ELC systems are on ISS. Each ELC site includes two data nodes. The ELC requirements call for a radiation-hardened 10BASE-T Ethernet interface at each data node. The requirement for ELC was to support a full receive version of the interface, and only to provide a link pulse to the attached payloads on the transmit side of the interface. Further development required a full duplex version of a radiation-hardened 10BASE-T Ethernet interface to support the SpaceCube program.

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Radiation-Hardened, Quad 12-Bit Digital-to-Analog Converter ASIC

This circuit incorporates science-driven features based on applications in a realistic space environment. Goddard Space Flight Center, Greenbelt, Maryland This radiation-hardened, compact, low-power, quad 12-bit digital-to-analog converter (DAC) application specific integrated circuit (ASIC) incorporates science-driven features based on applications in a realistic space environment such as threshold setting, current bias circuits, and general-purpose DC voltage generation. It is based on a previous 10-bit DAC that exhibited excellent test results, presenting the possibility of a 12-bit design.

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Use of Eccentric Bushings to Precision-Locate Multiple Parts on a Large Mating Structure

Lyndon B. Johnson Space Center, Houston, Texas Cups/cones are being used to provide a shear load transfer capability on a large separation interface that uses multiple discreet retention and release (R&R) devices (such as frangible nuts, separation nuts, separation bolts, etc.). To both provide good shear load-sharing among all R&Rs and to prevent relative motion between the mating structures, the cups/cones must be designed with minimal (and sometimes zero) radial clearance. This tight fit requires that the cup and the cone on the mating structures are precisely located to each other.

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Effective Packing of Large Panels via Scrolling and Origami Folding

The packing mechanism employs an origami configuration that may have sport and military applications. NASA’s Jet Propulsion Laboratory, Pasadena, California There is a need for large mirrors that can be launched to various bodies in the solar system in a packed form and unfolded to provide the required dimensions. The solution to the need for foldable panels that can be made as mirrors or other structures including antennas, etc. has been conceived using an origami configuration that is folded in two dimensions. The foldable panel configuration, if made as a mirror, allows supporting rover operation in craters and caves that are shadowed and inaccessible to direct sunlight. The benefits of its use include providing light to the solar cells of the rover, providing a heating source using sunlight, and illuminating the area of operation where the rover is located.

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Six-Degree-of-Freedom Control With Only Eight Thrusters

Even as few as eight thrusters can provide six-degree-of-freedom control of a spacecraft and do so without undesired coupling between torque and translational force generation functions. NASA’s Jet Propulsion Laboratory, Pasadena, California Typical spacecraft thruster configurations are often unable to provide full six-degree-of-freedom control and may have unwanted interaction between their attitude control and trajectory control functions, have undesirably high instantaneous electrical power demands, and use more thrusters than desirable. These last two potential problems gain increased significance if a spacecraft is required to have especially small size and mass, and have very low cost.

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