I was invited to give a presentation on my progress at the Space Access '16 Conference this past week. A copy of the presentation is located in the Media section. It includes some block diagrams of the H/W and S/W aspects of the flight computer as well as the ground equipment configuration.
The main hardware components for the flight computer are complete - photos of the CPU and Signal Conditioning PCBs as well as the flight computer mounted in the rocket are up on the photos page. The remaining work includes:
External power and debug connections
Transducer and servo wiring
After these items are complete, I can move on to proof tests, cold tests, and a hot fire test. I performed some preliminary EMI testing between the TM, GPS, and signal conditioning circuitry. As long as the TM antenna was at least a few inches away from the signal conditioning PCB, there was no measurable effect so it appears the filtering is working as intended.
As hardware is coming together, it seems like the pace of vehicle assembly is really picking up. Here is a photo of the overall vehicle progress so far (the nose cone is only temporarily mounted). There is a fair amount of work still to do for the S/W however. Most of the building blocks are in place so I'm going to incrementally add features as needed for the upcoming testing.
Instead of the five separate PCBs originally planned, I ended up with only three (Power Supply, CPU, and Signal Conditioning). A more distributed architecture is better for swapping out components and for testing but you also end up with more connections (that can fail) and a larger volume. After some thought, I decided to consolidate several functions onto the CPU PCB: the CPU, GPS, TM transceiver, IMU, digital pressure transducers, and the servo mux. It was a bit of a squeeze but I was able to get most of it on the front side of a 4x6 inch PCB with only the TM transceiver on the back. The signal conditioning PCB is the same as originally described. The Power Supply and Signal Conditioning PCBs are both two layers and the CPU PCB is four layers.
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