MotionSense IMU

MotionSense IMU

MotionSense IMU is a custom 2-layer PCB built around the ST LSM6DSM 6-axis accelerometer and gyroscope.

The board takes 5 V from USB-C, regulates it to 3.3 V, and breaks out the IMU's I2C interface and interrupt signal through a 5-pin header.

Hardware

• LSM6DSM 6-axis accelerometer + gyroscope
• AP2112K-3.3 LDO regulator
• USB-C 5 V input
• 4.7 kΩ pull-up resistors on SDA and SCL
• Decoupling capacitors for the regulator and IMU
• 5-pin interface header
• 2-layer PCB
• Board size: approximately 35 mm × 27 mm

Pinout

Design

The schematic and PCB were designed in KiCad.

During routing, I experimented with Quilter and Freerouting before bringing the design back into KiCad for final cleanup and verification.

The final design passes KiCad DRC with:

• 0 violations
• 0 unconnected items

Gerber and drill files were generated and inspected before manufacturing.

Schematic

The schematic includes the USB-C power input, AP2112K 3.3 V regulator, LSM6DSM IMU, I2C pull-up resistors, decoupling capacitors, and J2 breakout header.

The editable KiCad schematic is available in MotionSense_IMU.kicad_sch.

PCB Layout

The board is a 2-layer design with USB-C power input on one side and the I2C breakout header on the opposite side.

Manufacturing

Rev 1 was submitted to JLCPCB for fabrication and assembly in August 2026.

Five PCBs were ordered, with two boards receiving component assembly.

The 1×5 J2 header is intentionally left unpopulated and will be soldered manually during bring-up.

Files

• MotionSense_IMU.kicad_pcb — KiCad PCB layout
• MotionSense_IMU.kicad_pro — KiCad project
• MotionSense_IMU.kicad_sch — KiCad schematic
• BOM.csv — bill of materials
• MotionSense_IMU_Rev1_Gerbers.zip — Gerber and drill files
• pcb_3D.png — 3D board render
• pcb_layout.png — PCB layout image
• schematic.png — schematic image

Fabrication Files

The Rev 1 Gerber and drill files used for manufacturing are included in the repository.

Download Gerber + drill files

Current Status

Rev 1 has been ordered for fabrication and assembly.

The PCB design and manufacturing files are complete. The next stage is hardware bring-up and firmware validation once the assembled boards arrive.

Bring-Up Plan

1. Inspect the assembled board for soldering or placement issues.
2. Solder the J2 header.
3. Check for shorts between 3.3 V and GND.
4. Power the board through USB-C.
5. Verify the 5 V input and 3.3 V regulator output with a multimeter.
6. Connect an ESP32 to SDA, SCL, and GND.
7. Detect the LSM6DSM over I2C.
8. Read the WHO_AM_I register to confirm communication.
9. Read live accelerometer and gyroscope data.
10. Test the INT1 interrupt output.

Next Steps

• Prepare ESP32 bring-up firmware
• Complete electrical testing
• Validate accelerometer and gyroscope measurements
• Test interrupt functionality
• Document test results
• Record any changes needed for Rev 2

Project Goal

The goal of this project is to work through the complete PCB development process, from schematic capture and component selection through layout, manufacturing, assembly, and hardware validation.