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Electronics

docs/doc/hardware/consumer/electronics.mdx

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Board Overview

The Omi uses three interconnected PCBs:

BoardFunctionLatest Version
MainboardnRF5340 SoC, nRF7002 Wi-Fi, microphones, IMU, flash, battery managementv1.2
Charger BoardMagnetic dock with pogo pins, USB-C power, ESD protectionv1.0
FPCFlexible cable connecting mainboard to charging contactsv1.0

<Tabs> <Tab title="Mainboard" icon="microchip"> The main PCB carries all active electronics.
**Key ICs:**

| IC | Function |
|----|----------|
| nRF5340-CLAA | Dual-core Bluetooth LE SoC (application + network cores) |
| nRF7002-CEAA-R7 | Wi-Fi 6 companion IC |
| CSNP4GCR01-DPW | 8GB NAND Flash |
| LSM6DS3TR-C | 6-axis IMU |
| BQ25101YFPR | Li-Ion/Li-Poly battery charger |
| TPS628438YKAR | DC-DC buck converter |
| 2x MMICT5838-00-012 | TDK T5838 PDM microphones |

**Files:**

| File | Description |
|------|-------------|
| [`schematic.pdf`](https://github.com/BasedHardware/omi/blob/main/omi/hardware/consumer/electrical/mainboard/schematic.pdf) | Full schematic |
| [`gerbers/`](https://github.com/BasedHardware/omi/tree/main/omi/hardware/consumer/electrical/mainboard/gerbers) | Gerber + drill files for PCB fabrication |
| [`altium/`](https://github.com/BasedHardware/omi/tree/main/omi/hardware/consumer/electrical/mainboard/altium) | Altium Designer source project |

<Warning>
The nRF5340 (WLCSP-95, 4.4x4.0mm) and nRF7002 (WLCSP-81, 3.75x3.4mm) are fine-pitch wafer-level packages. Requires stencil + solder paste + reflow. Do not hand solder.
</Warning>
</Tab> <Tab title="Charger Board" icon="plug"> Magnetic charging dock with USB-C input.
**Key ICs:**

| IC | Function |
|----|----------|
| TPS25200DRVR | eFuse power manager (6.5V, 2.8A) |
| TPD1E10B06DPYR | ESD protection diode |

**Files:**

| File | Description |
|------|-------------|
| [`schematic.pdf`](https://github.com/BasedHardware/omi/blob/main/omi/hardware/consumer/electrical/charger-board/schematic.pdf) | Schematic |
| [`gerbers/`](https://github.com/BasedHardware/omi/tree/main/omi/hardware/consumer/electrical/charger-board/gerbers) | Gerber files |
| [`altium/`](https://github.com/BasedHardware/omi/tree/main/omi/hardware/consumer/electrical/charger-board/altium) | Altium source |

<Tip>The charger board is the simplest of the 3 — a good starting point if you're new to PCB assembly.</Tip>
</Tab> <Tab title="FPC" icon="link"> Connects the mainboard to the charging contact ring via a board-to-board connector.
**Key Components:**

| Component | Description |
|-----------|-------------|
| ST-BTB-K3570606M | BTB male connector (6+4P) |
| Charging contact ring | D9.9mm |

**Files:**

| File | Description |
|------|-------------|
| [`schematic.pdf`](https://github.com/BasedHardware/omi/blob/main/omi/hardware/consumer/electrical/fpc-board/schematic.pdf) | Schematic |
| [`gerbers/`](https://github.com/BasedHardware/omi/tree/main/omi/hardware/consumer/electrical/fpc-board/gerbers) | Gerber files |
| [`altium/`](https://github.com/BasedHardware/omi/tree/main/omi/hardware/consumer/electrical/fpc-board/altium) | Altium source |

<Warning>FPC is delicate — handle with care during assembly. The board-to-board connector has a limited insertion cycle count.</Warning>
</Tab> </Tabs>

How to Order PCBs

Upload the Gerber ZIP to any PCB manufacturer. Use the exact specs below per board:

ParameterMainboardCharger BoardFPC
Layers4 (F.Cu, In1.Cu, In2.Cu, B.Cu)22
MaterialFR4FR4Polyimide (flex)
Thickness0.6mm1.0mm0.3mm
Board Size21.0 x 21.0 mm13.0 x 20.0 mm29.3 x 12.5 mm
Surface FinishENIG (immersion gold)ENIGENIG
Min Trace/Space0.076mm / 0.076mm (3 mil)0.2mm / 0.127mm0.254mm / 0.1mm
Solder MaskBoth sidesBoth sidesBoth sides
Copper Weight1 oz outer, 1/3 oz inner1 oz1 oz
<Warning> The mainboard has blind vias (L1-L2, L3-L4) and buried vias (L2-L3) — confirm your fab supports these before ordering. Total 414 drill hits including 159 blind + 55 buried vias. </Warning> <Tip> Use **ENIG** surface finish for all boards. HASL causes bridging on the nRF5340 and nRF7002 fine-pitch pads (0.4mm). </Tip> <Card title="View Full BOM" icon="list" href="/doc/hardware/consumer/assembly"> See the complete Bill of Materials with all 88 components </Card>

First Power-On Checklist

<Steps> <Step title="Visual Inspection"> Check for solder bridges on QFN pads with a microscope or loupe. Verify all passives are placed correctly (check orientation of polarized capacitors). </Step> <Step title="Power Rails"> Connect bench supply (set to 3.7V, current limit 100mA). Measure VBAT (3.7V at battery input), VDD_nRF (1.0V for nRF5340 core), and VDDH (3.3V for nRF5340 I/O).
<Warning>If current draw exceeds 50mA before firmware flash, disconnect immediately — likely a short.</Warning>
</Step> <Step title="Flash Firmware"> Connect SWD debugger (J-Link or nRF DK). Flash using nRF Connect SDK. See [firmware guide](/doc/developer/firmware/Compile_firmware). </Step> <Step title="Verify BLE"> Open nRF Connect mobile app. The device should appear advertising as "Omi". If not, check 32MHz crystal and antenna matching network. </Step> </Steps>

Troubleshooting

<AccordionGroup> <Accordion title="Board doesn't power on" icon="bolt"> Check BQ25101 output (3.7-4.2V). Verify TPS628438 buck converter has correct input. Look for solder bridges on QFN pads with microscope. Measure resistance between VCC and GND — should be more than 1k ohm before power. </Accordion> <Accordion title="No BLE advertising" icon="bluetooth"> Verify 32MHz crystal is soldered (not just tacked). Check 32.768kHz crystal for RTC. Measure nRF5340 VDDH (should be 3.3V) and VDD (1.0V). Check antenna trace and matching network. </Accordion> <Accordion title="No Wi-Fi scan results" icon="wifi"> nRF7002 requires its own 40MHz crystal. Check BUCKA/BUCKB rails. Verify SPI connection between nRF5340 and nRF7002. Wi-Fi requires firmware support enabled. </Accordion> <Accordion title="Poor or no audio" icon="microphone"> T5838 microphones are top-port — verify sound inlet faces the enclosure acoustic holes. Check PDM clock (1-3.25MHz) and data lines. Both mics must be in the correct PDM channel (L/R). </Accordion> <Accordion title="Charging doesn't work" icon="battery-half"> Check pogo pin contact resistance (less than 0.5 ohm). Verify FPC connection. Measure charger board USB-C VBUS (5V). Check TPS25200 eFuse output. Verify magnet polarity alignment. </Accordion> </AccordionGroup>