20261024-2130-air-hub-carrier-part-reduction Air Hub / Air Hub Pro carrier revision D: part reduction

• status: completed
• priority: P2
• owner: worker/session-20261015-1500
• createdAt: 2026-10-24 21:30

Description

On 2026-10-24 the owner approved all items A-H of the carrier part-reduction review ("a-g全部做 H也做"):

• A. USB-C power path: a B360A Schottky into VIN instead of the LM74800 ideal diode, its FET pair and the EN/UVLO divider. The HUSB238 PD sink still requests 12 V. The LM74502 OV cut-off still gives USB priority.
• B. The long-press hardware reset (74LVC1G14, 2N7002, 1 M / 4.7 uF) is removed. TPS3823 MR_N is left open, and the watchdog covers hangs.
• C. RECOVERY and MASKROM keys become test pads.
• D. The debug UART header and the MG24 SWD header become pogo pads.
• E. Two status LEDs (SYS, RADIO) instead of four. The PWR and CAN LEDs are removed.
• F. TCAN3413 (3.3 V, STB tied low, as on the Mini) instead of the TJA1463.
• G. The 0 R in SDIO_CLK is removed.
• H. Air Hub variant: the Ethernet block (DP83825I, RJ45, crystal, straps, RMII series resistors, shield termination) is not fitted. Wi-Fi is then its only IP uplink.

Acceptance criteria:

1. Schematic: ERC 0 and net verification clean on air_hub and air_hub_pro. The Air Hub BOM marks the 433 MHz and Ethernet blocks DNP.
2. PCB: the Pro board is rerouted as revision D, with DRC 0 unconnected and 0 errors. EMC and SPICE are rerun.
3. Docs: spec, design, reference-board page, EMC evaluation, READMEs and cost record the changes and the new part count and cost.
4. Quality gate: bun run docs:lint && bun run docs:build && git diff --check passes.

ActiveForm

Reducing the Air Hub carrier parts (revision D)

Dependencies

• blocked by: (none)
• blocks: (none)

Notes

The Air Hub Mini is handled in a separate session and is out of scope. Its tooling now lives in tools/mini/.

Known trade-off of A: without M8, a 5 V-only USB source now reaches VIN at about 4.5 V. Before, the LM74800 UVLO kept it off. Behaviour of the K7805 and the core board in that case must be measured on the bench.

Result (2026-10-24): both variants regenerated as revision D, ERC 0 and net verification clean (542 pins, 226 nets); the Air Hub BOM marks the 433 MHz link and the Ethernet block DNP. The Pro board was rerouted: DRC 0 unconnected, 0 errors, 0 schematic-parity issues; EMC pre-check 59 findings (24 errors, all in the RJ45 pin field, RMII fan-out return vias, I/O filter false positives, buck harmonics and the USB_CON_DP layer change); SPICE 22 of 22 pass. Placed parts: Pro 127 -> 103, Air Hub 122 -> 71. Cost per board at 100 pcs: Pro $52.28 -> $48.24, Air Hub $42.69 -> $37.15. Spec R1.18, design R1.13, reference board R1.10, guide R1.10, EMC evaluation, product plan, READMEs and the enclosure (two light pipes) are updated. Not committed (owner instruction).