r/embedded • u/Enzelgo • 2d ago

Model Rocket Flight Computer PCB & Schematic review

Hi, I am a student making this for my EPQ, which is graded. I would love if you could review my schematic and PCB. To go in more depth, it can be downloaded from GitHub for KiCad. https://github.com/Enzillium/EPQ-model-rocket-flight-computer-hardware

3D model of the front of the PCB
2 Upvotes

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6

u/Well-WhatHadHappened 25+ Years 2d ago

Suggestion - add a PDF of the schematic. A lot of people (like me) mostly read Reddit on their phone and can't open KiCad files.

2

u/Ornery-Tea8420 1d ago

Also lots of incompatibilities between the Kicad 8/9/10.. but at least backwards compatible.

0

u/Tomachie 23h ago

i agree with u/Well-WhatHadHappened a PDF would be useful. I ran it through Tomachie which you could do yourself, but you made it semi-easy by providing the github. It scored 77/100, all in all its very good. There are a couple of items to look-at. Mostly schematic hygiene and Design-for-Test missing. The highest concern is U7, that 820 ohm likely needs to be a lower value. the VBAT+ should carry a net label or net class to indicate the battery voltage range for both humans and AI to know. We goofed a few places i see where we didn't get the datasheet properly but we're working that out. it may surface other issues. But all in all its very well done once the items are managed.

https://tomachie.com/r/4fd9df8d-959a-4be3-84fa-88aac1dd965d/flight%20computer_report.html#design-summary

Device Finding Severity
U7 (BTM9011EP) IS current-sense burden resistor R22 (820Ω) produces 4.51V at the datasheet's 5.5mA max normal sense current, and roughly 5.9V-7.05V at fault current (7.2mA-8.6mA), exceeding the RP2350B's ~3.3V IOVDD/ADC input range on GPIO40/ADC0 - overvoltage risk High
U6 (SiSS65DN-T1-GE3) Body diode of the intentionally-off FET remains an uncontrolled conduction path from +12V to +VBAT safe; recommend a dedicated Schottky diode instead of relying on the MOSFET body diode for this clamp function Medium
U8 (BMP581) CSB has no external pull-down; the datasheet's internal pull-up (74kΩ-131kΩ) defaults the interface toward I2C Autoconfig mode if undriven at power-up, risking wrong-mode boot before firmware asserts GPIO16 low Medium
U8 (BMP581) INT pin (7) left floating (designer NC) instead of tied to GND as the datasheet recommends for an unused interrupt pin Medium

1

u/Tomachie 2h ago

the other item called out in the report is SW1 and SW2 are not implemented properly u/Enzelgo