Expected duration: 1 - 2 weeks Summary: We’re looking to build a production‑ready prototype carrier board for the Raspberry Pi Compute Module 5 (CM5). The design must integrate **all sensing circuits on the PCB** (no off‑the‑shelf sensor modules): a gas sensor front‑end, an audio preamp path, and a motion (PIR) circuit. The board also provides **4× USB 3.x Type‑A data ports** via a PCIe‑attached USB host and powers from a **USB‑C 5 V** input.
What you will deliver • Complete schematic & 2 Layer PCB layout (your EDA of choice: Altium, KiCad, OrCAD/Allegro, etc.). • Manufacturing package: Gerbers, NC drill, fab notes, impedance targets, stack‑up, assembly files (BOM with MPNs, centroid), and 3D STEP. • Integrated sensor circuits (no modules): MQ‑2‑class gas element + heater driver & ADC interface; MAX9814‑class mic preamp + electret mic; PIR circuit (either discrete front‑end or digital PIR component). • USB subsystem: PCIe‑to‑USB3 host (e.g., VL805) → 4× Type‑A SS ports with per‑port power switches, PPTC, TVS, and ESD. • Bring‑up guidance: test plan, expected voltages, measurement points, and minimal CM5 config notes.
Key technical points (must‑haves) • No third‑party sensor **modules** on the PCB—use ICs/sensor elements only. • Gas: 5 V heater drive (≈150 mA class), divider/RC to 3.3 V ADC, analog filtering, optional PWM or on/off control. • Audio: onboard mic preamp IC (MAX9814‑class) with electret capsule, biasing, and anti‑aliasing before 10‑bit/12‑bit ADC. • Motion: integrated PIR front‑end. Preferred: digital PIR sensor (3.3 V) with minimal externals; acceptable: RE200B + BISS0001 discrete implementation. • USB: PCIe Gen2 x1 from CM5 to USB3 host; four SS connectors; per‑port VBUS switch (adj. ILIM ≈1.0–1.2 A), PPTC 1.5 A hold, VBUS TVS at connector; ESD on D+/D− and SS pairs. • Power: USB‑C 5 V sink‑only front‑end (RD pull‑downs), input protection, bulk caps, 3.3 V rail sizing for sensors & logic. • Grounding/routing: controlled impedance for PCIe/USB3; analog keep‑outs around mic/ADC; test points on critical nets. • 1 x Push button to GPIO • 1 x RGB LED to GPIOs
What to include in your proposal • EDA tool/version and recent USB3/PCIe + analog (audio/sensors) portfolio examples. • Your preferred PIR path (digital PIR part vs. discrete BISS0001+pyro) and why. • Notes on gas heater driving & calibration approach, and mic acoustic/mechanical plan. • Timeline by milestone and fixed‑price bid.
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