# Walter rear service study · R08

This is a mechanical and wiring study, not a full-head print release. Preserve the original R07 package. Only the upper rack is a changed printable component here. Reference shapes and empty allowances must not be printed as hardware.

The revised rack moves the four Pi standoffs to the rear face, retains the58×49mm mounting pattern, opens the SD-side rack edge and widens the side USB cable lane. The Pi faces the removable rear cover. The smooth external shell is unchanged.

## Two screens, two finished harnesses

Each small screen retains all eight wires. Specify a maker-assembled passive adapter with one40-way ribbon input and two separate8-way screen connectors. The adapter's copper traces distribute shared3.3V, ground, MOSI and clock. Each screen gets its own CS, DC, reset and backlight control. Maxwell does not splice wires or double wires into a terminal.

This is a custom adapter requirement, not an identified purchased product. The35×66×20mm space includes an assumed board and connector envelope only. No finished PCB layout, released connector pin order, selected mating connector, mounting bracket, or fabrication-ready Gerbers are supplied. A generic40-pin duplicator alone does not map two identical screen plugs onto separate control pins.

See `connection-plan.json`: signal rows use physical Pi pin numbers, not connector order. They follow WalterOS's local example, which enables third eye and disables heart. Check the actual deployed configuration, purchased screen labels,3.3V rail/backlight current and simultaneous screen operation. The40MHz example SPI setting is not evidence that long internal harnesses will work; test the chosen length and suitable clock rate on the bench.

## Rear service sequence to validate physically

1. Power down and disconnect power. Release rear-cover fasteners and any touch lead attached to the cover. Covers need final retention design.
2. Reach the Pi from the back. Unplug USB, HDMI, camera ribbon, GPIO ribbon and power using their connectors; do not pull on the wires.
3. Remove the four Pi screws from the rear. Support the board; cooler retention and screw lengths depend on the actual kit.
4. Lift the Pi assembly rearward. The SD-side opening is a proposed finger/card approach region; test card eject/grip and latch access with hardware.
5. Route and retain harnesses on the fixed rack. Provide removable strain relief and measured slack before refitting the back. No cable should rely on the removable shell for its only support.

## Every USB port needs its other end

The plan assigns touch, audio, microphone and radar to four distinct candidate Pi USB sockets. A fifth rear data port needs a selected hub or a different connection plan. The rear cover remains a blank. A panel socket must include its internal cable and a real upstream connection.

The USB audio dongle on the shelf needs a USB-A male-to-female extension (or a powered-hub connection). Its USB-A male plug cannot simply sit on the shelf. Actual connector overmolds, insertion travel and the route around the rack are unresolved.

Battery, regulator and USB power allocation remain unselected. A powered hub may solve both socket count and peripheral power needs, but its dimensions, upstream connection, supply and backfeed behavior must be checked against its actual documentation. No hub is certified to fit the old generic power allowance.

## What the checks establish

The browser's physical and reserved-space checks use the R07-derived simplified electronics envelopes. The official Pi major-component visual reference is separate and is clearly labeled; its extra small geometry is not silently included in those browser checks.

`GEOMETRY-CHECK.json` records current modeled intersections and a sampled board removal after its proxy attachments and rear pieces are excluded. It does not prove that a wired, fastened assembly can be removed.

`OFFICIAL-PI-RACK-CHECK.json` separately tests official Pi solids of at least0.1mm³ against the revised native rack. This checks the selected placement against the rack, not every cable, cooler, screw or shell component.

Connection lines are endpoint-bound intent guides, not fitted cables. They intentionally have no released cable length or bend-radius claim. A clear part/allowance result does not validate these lines. Real cable geometry and physical first-fit tests remain required.

R08 moves the Pi and its cooling intake; the old R07 heat animation does not apply to this layout. No CFD, fan performance or thermal approval is supplied.

## Maker's next concrete deliverable

Select the passive adapter connector families and supply two complete screen harnesses plus the40-way ribbon; measure their actual sizes. Confirm cooler, microphone, radar, camera and display connectors. Choose the power/hub topology. Then update mounts, cable solids, strain relief, fastener/tool clearance and thermal assumptions before quoting a full-head print. Start with the rack and original first-fit coupons against the actual hardware.

Sources: [Pi model and license](https://pip.raspberrypi.com/categories/892-raspberry-pi-5), [Pi interfaces](https://www.raspberrypi.com/documentation/computers/raspberry-pi.html), [screen signals](https://www.waveshare.com/wiki/1.28inch_LCD_Module).