ECU Layout and Schematic Changes

[Dat-Bois]

Just an issue tracker for the latest PCB layout as of 12/26/2024.

Layout

Layer Stackup:

• Ground plane with signal traces (RED)
• Primarily a ground plane with minimal traces (GREEN)
• Power Plane +24V (post REDs) (ORANGE)
• Power Plane +3.3V ECU, +3V3 REDS, +5V (NEON BLUE)
• Primarily a ground plane with extremely minimal traces (PINK)
• Ground plane with a lot of signal traces (DARK BLUE)

Parts layout:

• ECU is primarily on the left side of the board
• REDS is on the right
• Power regulators and LoRa radios are underneath (flat components)
• TCs + Solinoids on the bottom
• PTs on the top

Potential issues:

• Ethernet is in bottom right, based off images below unsure about wire bend radius (should be fine with a ribbon ethernet)
• Similar for USB-C connectors. May need either ribbon or 90deg bend connectors.

Things to do:

• Ground stitching as needed
• Initial review by those on this issue thread

[Dat-Bois]

Forgot the mounting holes. They have been adjusted to be about ~2mm closer to the edge of the board. In order to incorporate the bottom left hole I had to move the alarm circuit from there to the middlish of the board

Here is the hole pattern:

If the part it mounts to is already machined, we can 3d-print an adapter plate as needed (or I can really try squishing it).

[DanielHeEGG]

The USB traces are quite long, consider impedance match 90R differential.
Avoid vias in pad, makes manufacturing difficult.
GPS UART is reversed
GPS I2C is not longer used, remove.
ETHERNET UART is reversed
@cadguyen please confirm alarm circuit removal.

USB traces on layer In1 interrupts continuous ground return of high current traces.

TC SPI traces on layer In1 interrupts continuous ground return high speed MEM SPI.

Do you really need to flood layer In2 with 24V? it seems to be useless on the left side of the board. Consider pouring 3.3V to increase current capacity for the radio modules.

Some silkscreen with basic version tracking & also labels would be helpful.

Just some initial thoughts. We'll do a full PDR start of winter.

[Dat-Bois]

1. I'm not entirely sure how to do this within KiCad, is there a setting to make it 90ohm?. Also this will require impedance controlling the whole board for manufacturing right? Won't that be expensive (I've never done it before so idk)?
2. Resolved, some pads still have vias but those pads are very large and shouldn't be an issue I think
3. Resolved
4. Resolved
5. Resolved
6. Still waiting on alarm confirmation
7. Not entirely sure what you mean by this, for both of them there is still an uninterrupted ground plane either below or above them. Does this mean something different?
8. Same as 7
9. Split In2 into 3 fills. 3.3V on left side of board, 24V in the middle with the power circuits, GND on the right-most near REDS
10. I'll add silkscreen and versioning at the very end once everything else is finalized since otherwise it makes things difficult to see.

Sounds good, @cadguyen do you think you can help me make the PDR document?

[cadguyen]

Will help prepare PDR document for ECU 👍

Due to complexity and weight constraints, the alarm will no longer serve its original purpose to locate the rocket after it has landed. Instead, the alarm will be used for diagnostic feedback/debugging, so a piezo buzzer will suffice.

[Dat-Bois]

Alarm removed and buzzer added 👍

[Dat-Bois]

Resolved continuous ground issues (I think)

[Dat-Bois]

Latest commit addresses some issues from PDR:

• Fixed holes to be exactly 134mm x 84mm
• GPS shield removed and moved closer to antenna
• Reds Radio shifted to point towards the left side as well
• Resolved vias in pads issues (as far as I can tell)
• Specified part for 0.1Ohm current sense resistor

Things left:

• Increase Pad/Copper for the GS+ pads
• Add a ground via to nearly every single ground pad
• Add GS and Batt voltage readouts to ECU
• Update IOC file

[Dat-Bois]

Updates:

• GS+ pad copper increased
• Ground vias added and ground stiching done

Things Left:

• Add GS/Batt voltage to ECU
• Update IOC file
• Update silkscreen

[Dat-Bois]

All comments have been addressed: