README.md
# Smart ring flex — five-pin service revision
The index contains the routed flat PCB and individually selectable ring/dock assembly parts. Use PCB for the manufacturing view and 3D to inspect/hide assembly parts. `docked.circuit.tsx` shows the assembly; `cutoff-ring.circuit.tsx` and `wired-service-folded.circuit.tsx` show the separated ring/dock. `docked-preview.html` also provides a portable interactive assembly viewer.
The ring retains LIS2DW12TR, ZSPD4000QN with its separate LED supply, nRF52832 and BQ25186. Both photodiodes and green/red/IR LEDs remain. Its flush contact flex is internal; the dock has a retained bendable pogo carrier. External ring dimensions remain 28.4 mm OD / 20 mm bore / 9.2 mm width. Only the two copper contact faces show through the contact openings. No LEDs were added to the dock in this revision.
## Programming after cutting
The five retained bottom test pads remain exposed, 1.2 mm diameter on 2.54 mm pitch: TP6 reference 1.8 V, TP3 SWDIO, TP4 SWCLK, TP7 ground, TP5 reset. Optional bottom JSWD1 is beside the row, with separate routed connections; its pads and body do not overlap the probe pads. Minimum header-pad/test-pad gap is 3.220 mm and nominal bare-body gap is 3.620 mm. JSWD1 is **do not place**, excluded from factory BOM/CPL and normal assembly. All factory-populated components remain top-side.
J105 and JSWD1 use JST BM05B-SURS-TF(LF)(SN), C5306180. Numbered pin order at BOTH ends: **1 SWCLK, 2 SWDIO, 3 GND, 4 nRESET, 5 target 1.8 V reference input**. Reference is not a target power output or a charging rail. Use the numbered 1-to-1 JST A05SUR05SUR32W102A cable (DigiKey 455-4046-ND, 101.6 mm). The distributor's “reversed” housing orientation does not mean reversing numbered pins; the manufacturer GAM-280 drawing specifies the mapping. Verify cable continuity before use.
The ring header is an optional manually soldered service connection; install/remove it with the ring housing OPEN and the flex supported. The dock lid must also be open for the temporary cable. It is not a permanently fitted closed-housing port. The normal battery/charging assembly requires no user soldering. Do not directly connect a fixed 3.3 V programmer to the ring's 1.8 V signals.
The USB-C CH552 programmer candidate uses TXS0102 level translation for SWCLK/SWDIO and an open-drain reset stage. Its candidate CMSIS-DAP firmware builds, but has NOT been tested on hardware. First install the CH552 firmware using its WCH USB ROM bootloader/BOOT button, then verify USB enumeration, target reference, idle levels, sequencing and SWD operation on a current-limited bench before attaching the ring. nRF reset operation requires the appropriate UICR PSELRESET configuration. The full ring application is not supplied or validated.
**Firmware pin change:** CHARGE_DISABLE is now nRF P0.05 (QFAA pin 7), replacing P0.19. R25's external fail-off pull-up is retained. `firmware/ring-hardware-pins.h` documents the new mapping and safe initialization. Set output HIGH before enabling the GPIO output; permit charging only after valid battery-temperature checks. Do not use the former pin mapping.
## Validation and prototype limits
The current primary native build and independent physical copper audit pass with zero opens, shorts, clearance or edge violations. No electrical rules were relaxed to obtain this result. Existing parts, optical positions and ring envelope are preserved. The service section's stiffener is relieved to expose its pads; supplier fabrication/registration and mechanical support must be reviewed.
Build success is not manufacturing approval. Advisory native warnings and catalog placement-frame warnings remain. CPL origins, polarity, rotations and the assembler's selected models need manufacturer review. Pogo stroke/force/wear, printed fit, cable insertion, flex stackup and bend limits, stiffener adhesion, charging/power sequencing, unpowered-core behavior, low-battery green-LED compliance, RF/optical performance and first-flash/recovery require physical prototype tests. No waterproof, measured battery-life, clinical accuracy or completed step-counting/application claim is made.
Protected recovery baselines and rejected experiments remain local, outside the published source. No board order or purchase was made.