abse/museair-usb

docs/ASK-SWITCH-IMPLEMENTATION.md

# Raised ASK switch and separate cap

SW1 uses XKB TS-1102S-B-H-B / C480275, height code H=7.50 ±0.20 mm, nominal travel 0.25 mm, 160 gf. Manufacturer top-view numbering is upper left 1, upper right 2, lower left 3, lower right 4. Circuit diagram explicitly joins 1–2 and 3–4. Both terminals of the first pair are ASK; both of the other pair are GND. Pressing closes ASK to GND; the 10 kΩ pullup limits idle/pressed current to approximately 0.33 mA at 3.3 V.

SW2 RESET and SW3 BOOT use TS-1088-AR02016 / C720477. Unlike the four-terminal ASK part, their manufacturer diagram and imported footprint have only terminals 1 and 2. They are normally open; terminal 1 is EN or BOOT, terminal 2 is GND. The corresponding 10 kΩ pullups limit pressed current to approximately 0.33 mA. There are no duplicated common terminal pairs on these two-terminal parts.

Saved manufacturer PDFs are TS-1102S-B-H-B-datasheet.pdf and TS-1088-AR02016-datasheet.pdf. RESET/BOOT source: https://datasheet.lcsc.com/datasheet/pdf/0475ac02febf455ca9ddcfb380b0df0d.pdf?productCode=C720477 . `scripts/check-switch-pinouts.mjs` checks every terminal's source net and PCB pad; native DRC checks final copper independently.

The C480275 downloaded family model is the 4.5 mm variant. `correct-ask-switch-model.py` keeps imported XY geometry and maps body and actuator heights to 3.30 and 7.50 mm from the manufacturer's drawing. This is a documented derivative, not an exact vendor STEP of the H variant. The imported electrical footprint is unchanged. Its lands differ from the manufacturer's suggested 2.6 ×1.4 mm pattern; the imported lands are 1.8 ×1.2 mm and cover the model's terminals. Assembly/process approval remains a prototype check.

The cap is its own `ASK_BUTTON_CAP` group in assembly.circuit.tsx, selectable separately from `REMOVABLE_TOP_LID`; `showButton` also controls it independently. Cap stem Ø5.6 mm fits the Ø6.2 mm lid opening; its Ø4.2 mm underside cup accommodates the Ø3.5 mm actuator. The cap rests lightly on the actuator without the lid setting a preload. The head has a nominal 0.60 mm clearance above the lid at rest. Three lower snap fingers retain it, while allowing the operating stroke across switch height tolerance. These checks establish nominal CAD clearance only. Printed snap strain, tolerances, overtravel force, fatigue and button feel need physical testing before production.