DEC-103 - HID / USM Hub Connector Topology Rework

Field	Value
Decision ID	DEC-103
Status	Decided
Date	2026-09-17
Author	Izzyonstage & GitHub Copilot
Amends	DEC-087, DEC-088, DEC-089
Related	DEC-104

Context

The local Cypher HID assembly previously used a left connector pair for power / board ID / LED broadcast and a right connector pair for HID JTAG chain-through. The agreed redesign introduces a User Settings Module hub between Cypher and the HID boards and relocates the HID JTAG serial-data path onto a dedicated USM-facing connector.

Decision

• Retire the HID boards' former right-pair J5 / J7 connectors.
• Add one dedicated USM-facing right-edge connector to Cypher-Input and one to Cypher-Output.
• Repurpose Cypher J6 as the USM hub connector.
• Repurpose Cypher-Plugboard J2 to mate USM rather than a HID board directly.
• Keep the HID left pair in place mechanically, but redefine its pinout to carry the new ENC_DATA_IN[5:0], ENC_DATA_OUT[5:0], ENC_ACTIVE_INPUT_N, and ENC_ACTIVE_OUTPUT_N allocation.

Rationale

• Separates the HID serial-data path from the HID left-pair data / identity path.
• Lets USM serve as the fixed HID spine while keeping Cypher-Input / Cypher-Output order-agnostic.
• Moves the shared lighting-control and HID JTAG aggregation onto the same physical hub board.

Impact

• Cypher J5 and all mating HID / Plugboard left connectors adopt the new Template 1 pin map.
• Cypher J6, USM top / bottom connectors, and Plugboard J2 adopt the new Template 2 pin map.
• Cypher-Input J8, Cypher-Output J8, and USM left connectors adopt the new Template 3 pin map.