# E07: Tailor stock display interface decision

Review date: 2026-10-08. Research and the connector generator only; no native board changes or physical test. This supersedes the connector-research blocker, not the E06 electrical audit or manufacturing qualification.

## Decision and evidence status

Retain **Tailor TTH031BVS-04C**, with its **stock bonded CTP**, one 40-contact host connector and a revised enclosure. The exact MCU STM32U5G9VJT6Q already supports two-lane DSI; E05's unused DSI pins need new routing, not an assumed MCU replacement. E05 SPI connector/backlight routing cannot be reused unchanged.

| Item | Status | Evidence / remaining condition |
|---|---|---|
| Socket family / mating geometry | PASS, documentary | OCN drawing OK-14GM***-04 Rev.A and OK-14F***-04 Rev.B depicts the mating pair, 0.8 mm mating height. Module names OK-14GM040-04. Socket is OK-14F040-04. |
| Recommended socket land geometry | PASS, documentary | Factory drawing page 3 has 40-contact row and recommended PCB lands. A deterministic generator is provided below. |
| Electrical numbering convention | CONDITIONAL | OCN generic drawing has no pin numbers. Tailor p5 numbers the male contact view; the socket footprint explicitly mirrors this view. Physical pin1/end continuity and mounting orientation remain first-article checks. |
| Host CTP wiring | PASS, documentary | Tailor p5/p6/p7 places CTP SCL/SDA/INT/RST/VCC on 40-pin positions15/16/17/18/20. Six-pin OK-F501-06325 is shown in the internal sensor-to-LCM flex assembly. No second host CTP cable is required by this design. |
| CTP SCL/SDA voltage | PASS, documentary | Tailor labels both 1.8 V; use a 3.3↔1.8 V bidirectional I2C translator. |
| CTP INT/RST electrical contract | UNKNOWN | No exact CST3530 primary electrical/protocol datasheet was recovered. Configurable translation can prevent a fixed unsupported voltage choice, but does not prove operation. |
| Pin40 polarity | CONFLICT | Tailor p5 drawing says LEDK, p7 pin table says LEDA. Isolate it; never hard-wire either interpretation without verification. |
| Exact module initialization | UNKNOWN | Tailor p8 initialization section is literally TBD. ST7701 chip documentation alone cannot supply the glass-specific analog/gamma/timing initialization. |
| Supply loading / optical performance / physical fit | UNKNOWN until sample | Tailor provides voltage ranges but omits useful supply-current limits; no bench claims are made. |

## Sources

1. Tailor module V0, 2026-04-08, 18 pages: [official PDF](https://tailorpixels.com/wp-content/uploads/2026/07/TTH031BVS-04C-3.1-inch-IPS-TFT-LCD-480x800-MIPI-with-Capacitive-Touch-Screen-by-Optical-Bonding-brightness-of-500-nits-Typ.pdf). Local `research/E06/display/TTH031BVS-04C.pdf`.
2. OCN factory series drawings, PDF pages1/3: male Rev.A 2013-09-12; female Rev.B 2015-10-22, OCN title block and drawing number. [Distributor-hosted original drawing](https://www.krxdsc.com/index.php?a=custom_download_file&aid=1061&c=View&field=fjxz&m=home), linked from its [exact-part page](https://www.krxdsc.com/html/products/Connector/1061.html). Local `research/E07/display/OCN-OK14GM-OK14F-series.pdf`. Provenance is a manufacturer-authored drawing hosted by a distributor, not a fresh manufacturer-issued revision. Revision currency and procurement lot remain qualification checks.
3. Independent primary application corroboration: [Kai Lap Tech module](https://www.kailaptech.com/Product.aspx?id=1152&l1=) names OK-14F040-04 as its mating connector; [Sunyee UE035DV PDF](https://www.chinasunyee.com/UploadFiles/20191026152301650627.pdf), mechanical drawing, names the customer-side connector OK-14F040-04. These corroborate the part choice; they do not replace the OCN land drawing or Tailor pinout.

The official OCN site `http://www.ocn.tw` was reachable over HTTP. Its current online catalogue returned other BTB families; its linked `http://ocnmall.com/` homepage loads but product/search endpoints returned404. The exact-series drawing was subsequently recovered via the documented distributor download above. No vendor was contacted and no purchase made.

## Exact module pin contract

Source: Tailor PDF pp5–7. Names below use the module's logical pin numbers, not an arbitrary CAD odd/even pin assignment.

| Pin(s) | Tailor function | E07 connection / treatment |
|---|---|---|
| 1,2,39 | LEDK | `LCD_LEDK`, regulated backlight return; **not automatically GND** |
| 3 | LCM_ID(GND) | GND |
| 4,5 | LEDA | `LCD_LEDA`, boosted constant-current driver output |
| 6,19 | NC | No connection |
| 7,8,13,14,21,23,26,29,32,35,38 | GND | Ground |
| 9 | LCM_RST | Active-low reset, module voltage domain |
| 10,11 | IOVCC | 2.85 V is inside the published 1.8–3.3 V operating range |
| 12 | LCM_TE | Optional output; unconnected in planned video-mode implementation |
| 15 | CTP_SCL(1.8) | `CTP_SCL_1V8` |
| 16 | CTP_SDA(1.8) | `CTP_SDA_1V8` |
| 17 | CTP_INT | Translated interrupt; exact electrical behavior still unverified |
| 18 | CTP_RST | Translated reset; exact thresholds/timing still unverified |
| 20 | CTP_VCC | 2.85 V within published 2.5–3.6 V; typical label2.8 V |
| 22 | VDD | 2.85 V within published 2.5–3.6 V |
| 24,25 | D2P,D2N(NC) | No connection |
| 27,28 | D1P,D1N | `DSI_D1_P`, `DSI_D1_N` |
| 30,31 | CLKP,CLKN | `DSI_CLK_P`, `DSI_CLK_N` |
| 33,34 | D0P,D0N | `DSI_D0_P`, `DSI_D0_N` |
| 36,37 | D3P,D3N(NC) | No connection |
| 40 | LEDK on p5; LEDA on p7 | `LCD_PIN40`, two alternative 0-ohm links to LEDA/LEDK; **both DNP default** |

The pin40 option is a safe way to avoid committing the contradictory interpretation. It is not evidence that the module works with pin40 floating. On an unpowered module, verify which existing LED group pin40 connects to; populate exactly one appropriate link only after that result. Never populate both links.

The internal six-contact touch definition on p5 is 1GND,2SCL(1.8),3SDA(1.8),4INT,5RST,6VCC(2.8). The main 40-pin already exposes the same signals. Generic eight-pin CTP cable pinouts from other modules must not be applied.

## Socket footprint derivation

`tools/e07/display_connector.py` owns only `BMC:OCN_OK_14F040_04`; `register_display_footprints()` writes that one local footprint. `footprint_text()` is side-effect-free and was checked with the project S-expression parser for 40 unique numbered contacts and four unnumbered retention pads. Root owns generation and native CAD validation.

All dimensions are mm, viewed from the host PCB component/front-copper side:

| Feature | Value / derivation from OCN p3 |
|---|---|
| Body | 10.50×2.50 nominal; drawing A10.50/B9.40/C7.60 for40contacts |
| Pitch and contact span | 0.40; 20contacts per row span7.60 |
| Contact lands | 0.23×0.50; outer row envelope2.90 minus inner gap1.90 gives0.50 length |
| Contact centers | x=-3.80+0.40*i, i=0…19; y=±1.20 |
| Retention lands | 0.70×0.65; outer envelope2.90 / inner gap1.60 |
| Retention centers | x=±4.75 from3.80+1.30−0.35; y=±1.125 |
| Contact number convention | Lower row1…20 from left to right; upper row40…21 from left to right |
| Mating | 0.80 board-to-board; female physical height0.77±0.10 |

Tiny chamfers illustrated on the retention lands have no dimension in the drawing; the generator uses their rectangular envelope and explicitly records that fabrication choice. Courtyard/silkscreen are project drafting choices, not dimensions asserted by OCN. Retention pads are mechanical and unnumbered, with no invented electrical connection.

Numbering derivation: Tailor p5 shows the male on the extended flex with right column1(top)…20(bottom), left column40(top)…21(bottom). After rotating the long axis horizontal and reflecting the contact face to the opposing socket mating face, the chosen host row convention above results. Do not reinterpret it as alternating odd/even numbering, and do not mirror it again merely because the finished board is displayed from the rear. Placement on B.Cu must use KiCad's normal footprint flip. Because the OCN series drawing omits its own electrical numbering, first-article mating/continuity remains a distinct gate.

## Remaining functional gates

- Stock assembled module must match V0's actual connector and flex position. Stock cover glass is47.73×80.96mm; total3.08±0.15mm. This is larger than the earlier custom-glass concept and requires its enclosure update.
- Use a true six-series-LED driver: Tailor p5 specifies VF19.2V, IF20mA; the 15–20mA recommendation on p7 supports an initial15mA setting. E05's low-voltage CAT4104 arrangement does not supply this string.
- Obtain or measure the exact CST3530 I2C address, register protocol, reset/IRQ timing and voltage contract. Do not assume an FT5426/GT911 address or packet format. Default1.8V GPIO translation plus a mutually-exclusive2.85V option provides hardware adaptability only.
- Obtain the exact TTH031BVS-04C ST7701 initialization sequence and video timings. Generic ST7701 init arrays may light a different panel while being wrong for this glass.
- Verify power-up sequencing, current/headroom, DSI electrical behavior and signal integrity on hardware. Neither ERC/DRC nor a fully routed footprint proves those functions.

The documented socket geometry now permits native PCB layout. Production/working-display sign-off remains blocked by the explicitly listed sample/firmware qualifications; these must not be hidden behind a CAD PASS.

## Evidence hashes

- Tailor PDF SHA256: `e4f6866168aba43d36d1dbd5122bbf67a64fba0bb561458ac76811f32b0e9b81`
- OCN drawing PDF SHA256: `c567fe71e16d19d49b3c8a51ec8474e1e0c96fa4376653eca1dd662889599d26`