10-002 — Hardware Profile

Purpose

Define the camera-free hardware profile and the DIY bed-vibration extension. Scope updated 2026-09-06; new hardware selection and validation remain pending.

Bill of materials

Item	Requirement	Remaining decision
compute	Raspberry Pi 3 B+ revision 1.3 (a020d3)	enclosure validation
storage	high-endurance microSD, at least 16 GiB	manufacturer/capacity
audio	HiFiBerry Amp2 with two passive speakers	acoustic validation
main power	regulated 16.5 V / 2 A through Amp2 for bring-up	measured margin with final peripherals
tactile control	dedicated motor driver or simple oscillator/amplifier	stable Nerves interface, progressive response and cutoff
tactile actuator	one enclosed vibrating motor or tactile shaker, frame-mounted	occupied-bed distribution, start threshold, inertia and noise
tactile power	dedicated external certified supply, low-voltage protection and cutoff	voltage/current, gain limit and thermal validation
control	physical dismiss/snooze button	installed button/link and end-to-end validation
time	external I²C RTC recommended when offline	model

Camera and infrared illumination are removed from the bill of materials. There is no bed-presence sensor. Tactile hardware is optional for operation, but its three use cases are part of the P1 prototype scope.

The priority is felt vibration with progressive intensity. Accurate frequency, audio reproduction and a second sound card are not hardware requirements.

Integration constraints

HiFiBerry uses I²S and part of the GPIO header. Record conflicts with the physical button, its radio link and any RTC before wiring. Keep speaker outputs on the Amp2; a separate power stage drives the tactile actuator. GPIO may carry logic commands to a compatible driver only, not actuator current. Do not bridge Amp2 outputs or power the actuator from GPIO or the Pi’s 5 V rail. Protect a motor driver against inductive transients and overcurrent; keep rotating masses captive.

The bed has a slatted base. Couple the actuator rigidly to a load-bearing frame crossmember or to the surrounding casing only if it is structurally connected to that frame. Use a removable plate; verify transmission through the slats and mattress with the bed occupied. Dimensions and coverage of sleeping places remain open. Isolation pads must not compromise bed stability or load capacity.

The enclosure must provide ventilation, cable retention, protected terminals, restricted microSD access, and separation of hot parts from bedding. Verify each power circuit with at least 25% margin over measured peak demand.

Capability profile

At startup, adapters publish availability and manufacturer/model when detectable. Select HiFiBerry and the chosen tactile interface by stable configuration. USB audio is optional; if selected, its addressing must not depend on enumeration order. Disabled or uncalibrated vibration is an explicit inactive state, not a fault. Requested but unavailable vibration reports degradation without blocking sound. Camera absence is normal and must not affect startup or health.

Hardware decision register

ID	Question	Expected evidence
HW-DEC-001	Raspberry Pi 3 B+ rev 1.3 (a020d3)	verified 2026-08-20
HW-DEC-002	HiFiBerry Amp2	verified with hifiberry-dacplus and stable card name
HW-DEC-003	Retired: camera candidate	removed 2026-09-06
HW-DEC-004	Retired: IR illumination	removed 2026-09-06
HW-DEC-005	power supplies	measured budget per circuit
HW-DEC-006	RTC requirement	intended offline behaviour
HW-DEC-007	actuator technology, count and mounting	trial enclosed motor first; shaker alternative if smoothness/noise requires it
HW-DEC-008	controller, power stage and tactile supply	logic interface, load/current, cutoff, coasting and temperature; no mandatory DAC

Requirements

• HW-001 — Retired: illuminator power constraint.
• HW-002 — Audio hardware shall be addressed by a stable identifier.
• HW-003 — GPIO/I²C/I²S conflicts shall be documented before wiring.
• HW-004 — Retired: camera framing.
• HW-005 — Retired: camera-loss behavior.
• HW-006 — The electrical budget shall include 25% margin over measured peak.
• HW-007 — Tactile power shall use a dedicated protected circuit with no load on the Pi’s GPIO/5 V power rails and no shared Amp2 speaker output.
• HW-008 — Frame coupling, fixation, bed stability, distribution, thermal load and floor noise shall be validated on the actual occupied bed.
• HW-009 — Audio and vibration devices shall remain correctly assigned across controller reconnect/restart; USB enumeration applies only if that variant is used.

Acceptance criteria

Record assembly photographs, wiring, overlays, device detection, per-circuit idle/load measurements, cutoff results, and a 30-minute wake/breathing run plus prolonged music validation. Camera capture and optical tests are not gates. See bed vibration and validation milestones.