Schematic review: ESP32 engine vibration + ignition logger (3 boards)

[u/MichealScott34]

Hey everyone, I'd love a schematic review before I start the layout.

I am designing a little logger for diagnosing car engines for a class. An accelerometer board goes on the engine to pick up vibration, and a spark detection board goes on an ignition coil to check that it's firing (kind of like a coil-on-plug tester). Both connect to the main ESP32 board with wires, so it's 3 separate PCBs.

Main board (ESP32-WROOM-32E):
- USB-C with a CP2102N for programming
- Single-cell Li-ion with a BQ24072 charger and MAX17260 fuel gauge
- AP7361C 3.3V regulator with an external on/off switch
- Optional connector for a NEO-7M GPS module

I've used this same ESP32 + CP2102N auto-reset setup before, but auto flashing never worked. I had to hold the BOOT button every time I wanted to upload code. If anyone can spot why, that'd be awesome.

Accelerometer board:
- KX134 (±64g) over SPI

Spark detection board:
- Pickup wire to RC filter, TVS and clamp diodes to 74HC14 Schmitt trigger to ESP32

Any feedback is welcome, thanks!

[u/Enlightenment777]

This comment is posted on all reviews.

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Please make sure your review post adheres to:

• subreddit rules (#1 to #6), review rules (#7), review image rules (#8), see link.

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Please fix these common schematic layout issues: (if yours has any of these issues)

• Don't allow text / lines / symbols to touch each other, and don't draw lines through symbols.

• Use correct reference designators (RefDes), and renumber to remove numeric gaps, see tips.

• For positive voltage circuits, point positive power rail links upwards and grounds downwards (maybe sideways), see tips. For negative voltage circuits, point negative power rail links downwards and grounds upwards (maybe sideways). For bipolar circuits, maybe point grounds sideways.

• Place decoupling capacitors vertically below postive power rail lines with ground on bottom side of the capacitor. Place capacitor next to IC symbol, and connect a line to IC positive power rail pin, see tips and example.

• Place pull-up resistors vertically above signal lines, and place pull-down resistors vertically below signal lines, see example and tips.

• Reasonably minimize the use of unique net labels, because everyone hates hunting for them!! Single resistors / capacitors / diodes should not sit by themselves, instead move & connect them with a line to their circuit.

• More schematic conventions / guidelines / tips - 1, 2, 3, 4.

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Please fix these common PCB layout issues: (if yours has any of these issues)

• Silkscreen - add board name / board revision number / date (YYYYMMDD, YYYYMM, YYYY) for traceability.

• Silkscreen - add pin 1 indicator next to ICs & connectors (not under parts). For polarized capacitors, add "+" next to positive pin. If part is through-hole package, place indicator on both PCB sides. See 1, 2, 3, 4.

• More PCB conventions / guidelines / tips - 1, 2, 3, 4, 5.

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