Looking for PCB review/feedback — STM32F411 motion data logger with USB-C, SDIO microSD, SPI IMU, RTC backup
The board is intended to work as a small motion/event data logger or “black box” for robotics applications. The idea is to mount it on a robot or moving system, record IMU/current-sensor data, store logs on a microSD card, and communicate with a host such as a Raspberry Pi or Jetson through USB/UART.
Main features:
MCU: STM32F411CEU6
USB-C: used for power and USB data
IMU: BMI088 connected through SPI
Storage: microSD card using SDIO 4-bit mode
RTC: internal STM32 RTC using 32.768 kHz LSE crystal
Backup power: coin cell on VBAT to keep RTC time when main power is removed
Debug: SWD/ST-LINK header
Analog input: current-sensor input through JST, filtered before going into the STM32 ADC
Extra interface: USART/UART pins for telemetry or external sensor communication
For the stackup, I’m using a 4-layer structure:
L1: Signal + components + local power routing
L2: Solid GND plane
L3: Solid GND plane
L4: Signal + power routing / polygon pours
I decided not to use a dedicated inner power plane. Instead, I’m using solid continuous ground planes on both inner layers so that the signal and power routing on the outer layers always have an adjacent ground reference. Power is distributed using wider traces and polygon pours on the outer layers.
My goal with this stackup is to improve return paths, reduce EMI risks and maintain signal integrity. In the routing of the IMU and the microSD Card Socket, I feel that I have overused vias a bit. Does my use of vias in this scenario affect the performance of the board (signal integrity and EMI)?
Things I would especially appreciate feedback on:
USB-C routing and protection
SDIO microSD routing and pull-up placement
SPI routing to the BMI088 IMU
RTC crystal/VBAT layout
Grounding strategy and the two-inner-ground-plane stackup
Power distribution using polygon pours on the outer layers instead of a power plane
Any obvious schematic/layout mistakes or manufacturability concerns
I’m still learning PCB design seriously, so any comments about layout, signal integrity, grounding, EMI, component placement, or general design choices would be really helpful.
Thanks in advance!