Requirements

The mission FloripaSat I has important requirements for each module. So, the OBDH, to attempt this, has several hardware and software implications. The content below will presents the main necessities, decisions and implementations to the OBDH.

1. The OBDH shall interface with at least 3 Solar Panel sensors, in the faces -X,- Y and -Z.

2. OBDH shall have a watchdog timer to perform a microcontroller reboot if its main execution stucks for more than 1 second, with 2 more seconds of tolerance.

3. The OBDH shall interface with the main radio over SPI protocol (@2 KHz) with an error less than 1%.

4. OBDH shall perform measurements of its microcontroller internal temperature (±5% error), at least, at the sample rate of 1 measurement every 10 seconds.

5. OBDH shall perform measurements of its microcontroller supply voltage (±2% error), at the sample rate of 1 measurement every 10 seconds.

6. OBDH shall perform measurements of its supply current (±5% error), at the sample rate of 1 measurement every 10 seconds.

7. OBDH shall read IMU data, at least, at the sample rate of 1 measurement every 1 seconds. The accelerometer measure shall have less than 2% error. The gyroscope measure shall have less than 2% error.

8. OBDH shall read Solar Panels sensors, at least, at the sample rate of 1 measurement every 30 seconds. It will read temperature and sun sensors.

9. OBDH shall count the time, in minutes, that it is powered on. Every time that a reset occurs, the seconds counter shall reset, so the counter will just count complete minutes.
Relates to Item 5 of System Requirements

10. OBDH shall store all acquired data in a non-volatile memory (the sort of data can be find here). The total memory capacity shall be at least 1 GB. Shall be an alternative non-volatile memory with at least 32MB, that shall be used if the primary stops working.
Relates to Item 16 of System Requirements

11. The OBDH shall recover itself from a reset without no losses: do not lose the time counter since power on and the stored data.
Relates to Item 9 and 10 of OBDH Requirements.

12. The OBDH shall perform antenna deployment (at least the antenna connected to the main radio), over a I²C interface (@100KHz). The status (deployed or not deployed) shall be verified every time that a reset occurs. When the status is “not deployed” the OBDH shall hibernate for 45 minutes and do the deployment.
Relates to Item 19 of EPS Requirements

13. The OBDH shall interface with the EPS module. Over I²C (@100KHz), as a master node.

14. The OBDH shall interface with the TT&C microcontroller.

15. The OBDH shall send to TT&C microcontroller the data to send through Beacon, with an error less than 1%.
SSR 10

16. OBDH shall be able to take subframes of the stored data in non-volatile memory to send over the downlink according some telecommand request.

17. OBDH shall be able to send critical data periodically, once per minute.

18. OBDH shall be able to choose between send critical data periodically once per minute, once every 2 minutes or do not send, according the energy level and operation mode.

19. OBDH shall know the predefined expected maximum time that each task should run.

20. OBDH shall reset a task execution if it exceed its pre-defined maximum execution time.

21. OBDH shall change its execution mode based on predefined schemes based on available power.
Relates to Item 22 of System Requirements

22. The OBDH shall agree with TT&C microcontroller what kind of transmission (Beacon or Telemetry) may be done at a time.

23. The OBDH on-board software shall perform NGHam data package encoding and decoding.

24. The communications with other modules (EPS and TT&C) shall have a way to verify if the received data is correct (CRC).

25. The communications with other modules (EPS and TT&C) shall have less than 1% of failure in transmissions.

26. The communications shall be reset tolerant. Interrupted transmissions shall not harm the OBDH operation.

27. The OBDH shall have UART (@9600 bps) communication for debugging. This interface shall be outsourced to be able to connect when the cubesat is mounted.

28. The OBDH shall warn the TT&C microcontroller when enter in a shutdown mode.
FCC and IARU regulation.

29. OBDH shall be able to respond to command requests at least a time per second.
Relates to Item 17 of System Requirements and Item 18

30. OBDH shall obey to a public command that can shutdown the transmissions for 24 hours. In this mode, the routines can keep doing the same but the downlink transmissions shall be ceased.
Compliance with AMSAT/IARU regulations and SSR X.

31. OBDH shall be able to keep in shutdown mode until reach 24 hours even if a reset occurs.
Compliance with AMSAT/IARU regulations

32. OBDH shall be able to restore by itself from the shutdown mode after 24 hours.