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Pyxida is the custom avionics system designed for use in Project Therion, and applied in future projects. The specifications for the original system were picked during the fall 2015 semester and have been refined several times since then.
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Pyxida Rev. 2 was a minor upgrade from the original version, completed during Spring 2016. It retained the BeagleBone cape form factor of the original revision, but had its own 3.3v power so it could run the XBee more reliably and could be operated independently from the BeagleBone. It also featured standard headers for connections to other devices instead of the JST connectors used on Rev. 1. This version added continuity checking as well as battery voltage checking, though this feature required the use of the BeagleBone. As IREC 2016 drew closer, it became clear that the BeagleBone added too many complications to justify its place in the system, so it was removed and its software was ported to C++ and added to the firmware of Pyxida itself. This was the configuration used for the IREC 2016 competition flight.
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Pyxida Rev. 4 was a minor revision completed during the 2017 Spring Semester. It includes an upgraded GPS module and support for active GPS antennas.
Revision 5:
Pyxida Rev. 5 was a major revision that included a new radio chip (CC1120) to replace the old xBee radio add on. Rev. 5 Also included a new breakout board expansion to allow more modules to be added to Pyxida without the need for an entire redesign and manufacturing of a new board. Breakout for this revision included a barometer breakout, programmer breakout, and pyro breakout. Unfortunately, this revision had several hardware issues (mostly related to manufacturing) that had to be resolved with a new revision.
Revision 6:
Pyxida Rev. 6 was a major revision completed during the 2018 Fall Semester. It includes a new breakout design using ribbon cables instead of pins to allow for more flexibility in placing breakouts in the avionics bay. It has a new radio chip (CC1200) and a radio amplifier (CC1190) to allow for longer range communication. It has a new backup battery system, and includes a LIPO charging feature, and allows for external batteries to be connected to Pyros if higher voltages are needed.
Revision 6 I2C Addressing:
Wire0: (Wire in code)
- 0x77 BMP280
- 0x68 MPU9250
- 0x53 ADXL275
- 0x42 UBLOXMAX8
Wire1
- 0x20 MCP23008
Wire2 (Breakout Wire)
- 0x?? BBC
Revision 6.1:
Pyxida 6.1 is a minor revision to Pyxida 6 made in September 2019. It implemented the following changes relative to Pyxida 6:
- Fixed minor Buzzer footprint issues
- Corrected an inductor value error in the CC1200 PA output (L601)
- Replaced BMP280 with MS5607 (7-bit Address 0x76)
- Replaced CC1200 XTAL with TCXO
- Changed through hole SMA to edge launch
- Connected bottom layer of RF section to GND, added via stitching
- Replaced power traces with planes in the 3rd inner layer
Bugs: Footprint of TCXO incorrect, required re-routing of 2 traces.
Pyxida 6.2 Suggested Edits:
- Fix TCXO footprint
- Add vias under MCP23008 (Pyro I/O expander) and MPU9250 to wick extra solder from the ground pad
- Had issues with these parts not soldering correctly and getting lifted up due to excess solder on the central pad
- Label test points on the bottom of the board
Firmware
Pyxida runs firmware written in Arduino-dialect C++. It follows a state machine architecture, with software objects that represent physical hardware. States are represented as objects that subclass a base state and provide functions for state entry, exit conditions and destinations, and system behavior while in the state. States can access hardware such as pyro channels and the board's radio through the previously-mentioned hardware objects and use these objects for input and output.
Delete me:
Firing:
4
5
6
7
Continuity:
3
2
1
0