> ## Documentation Index
> Fetch the complete documentation index at: https://docs.omi.me/llms.txt
> Use this file to discover all available pages before exploring further.

# Electronics

> PCB design files for the Omi mainboard, charger board, and flexible PCB — Altium source, Gerber files, and schematics.

## Board Overview

The Omi uses three interconnected PCBs:

| Board             | Function                                                                | Latest Version |
| ----------------- | ----------------------------------------------------------------------- | -------------- |
| **Mainboard**     | nRF5340 SoC, nRF7002 Wi-Fi, microphones, IMU, flash, battery management | v1.2           |
| **Charger Board** | Magnetic dock with pogo pins, USB-C power, ESD protection               | v1.0           |
| **FPC**           | Flexible cable connecting mainboard to charging contacts                | v1.0           |

***

<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:

| Parameter       | Mainboard                      | Charger Board   | FPC              |
| --------------- | ------------------------------ | --------------- | ---------------- |
| Layers          | 4 (F.Cu, In1.Cu, In2.Cu, B.Cu) | 2               | 2                |
| Material        | FR4                            | FR4             | Polyimide (flex) |
| Thickness       | 0.6mm                          | 1.0mm           | 0.3mm            |
| Board Size      | 21.0 x 21.0 mm                 | 13.0 x 20.0 mm  | 29.3 x 12.5 mm   |
| Surface Finish  | ENIG (immersion gold)          | ENIG            | ENIG             |
| Min Trace/Space | 0.076mm / 0.076mm (3 mil)      | 0.2mm / 0.127mm | 0.254mm / 0.1mm  |
| Solder Mask     | Both sides                     | Both sides      | Both sides       |
| Copper Weight   | 1 oz outer, 1/3 oz inner       | 1 oz            | 1 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>