GR716-based Cubesat Controller
GR716-based Controller: A modular small-sat platform
The GR716-based cubesat board is an adaptable small-sat platform centered on a LEON3-FT microcontroller by Cobham Gaisler that is tailorable for specific use-cases through a mezzanine interfaced to the GR716 via dedicated multi-function I/O (UART, PWM, SPI, I2C, CAN, RS422 /-485). Applications include in-flight testing of COTS devices or otherwise, data processing through the inclusion of a payload processor, hosting Xilinx Kintex UltraScale- or Virtex FPGAs and performing programming, scrubbing and control (via a parallel SelectMAP interface, becoming available in a future, pin-compatible iteration of the GR716), or acting as a general purpose low-power controller. Mezzanine power can be derived from a common 5V supply, or the 3.3V supply generated on the main board may be used directly (up to ~2A).
External interfaces to allow the board to interface to a greater system are available and comprise 26 multi-function GPIO (26x PWM, 1x I2C master/slave, 1x SPI w/3 SLV, 3x UART, 4x ADC, 4x DAC) as well as dedicated interfaces (2x CAN, 1x I2C, 1x RS422/-485, 1x SpW, 1x AHB UART, 1x Debug UART for debugging/SW upload).
A future iteration of the microcontroller will also provide SpaceWire router-, CAN-FD- and 10/100Mb Ethernet capabilities, in addition to the mentioned SelectMAP interface, as well as internal non-volatile memory.
2x 4Mb of redundant Cypress FRAM is available on-board as boot memory with automatic fall-back, and 128MB of Micron SPI FLASH is available for storing non-critical data. Through configuration of bootstrap signals, the board is bootable- and controllable remotely via SpaceWire, UART or I2C. Latch-up mitigation/power-gating of susceptible on-board devices is achieved through a reliable load-switch + current/voltage monitoring circuit combination, which also allows acquisition of housekeeping telemetry via the on-board I2C bus.
The board is built on a standard PC104 form-factor, is designed according to the TEC-ED IOD Board Specification, and consumes ~1W in the worst case, produced via high-efficiency (>90%), reliable DC-DC converters from Analog Devices. An initial prototype of the main board has been produced, and board files (schematics, layout, bill of materials) are available in an internal repository on the ESA Gitlab.