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20260927-1640-air-hub-low-cost-linux-and-lora-star Evaluate low-cost Air Hub Linux platforms without the industrial and native-CAN constraints, and a proprietary LoRa star for Air Hub LR

  • status: completed
  • createdAt: 2026-09-27 16:40
  • approvedAt: 2026-09-27 17:05 (owner: "可以开始处理")
  • relatedTask: 20260927-1640-air-hub-low-cost-linux-and-lora-star

Context

章节标题：“Context”

Current direction (spec R0.6, design R0.4): industrial −40…+85 °C Linux SoC with native CAN, RK3506J (alt. T113-i), chip-down or core board; ≥256 MB (LR with local network server ≥512 MB); ARMv5 excluded only because Node.js (zigbee2mqtt, matter.js) does not support it. Family rule (PRODUCT-PLAN §1): −25…+70 °C operating; Air Hub environment target −20…+60 °C.

Findings of 2026-09-27 (LCSC via jlcsearch, vendor pages and datasheets):

  • Cheapest current option: Forlinx FET3506J-S / FET113i-S 88 CNY (configuration of J-S unpublished) → Air Hub about $33–49, LR about $45–70.
  • Ebyte core boards: only ECK30 T113-i is −40…+85 °C. ECK30-T13IA2MN2M-I stamp-hole, 2×CAN, 256 MB / 256 MB NAND, LCSC about $19.1 (stock 1); ECK30-T13IC2N2-I BTB, CAN not listed, LCSC about $20.4, Ebyte store $56.9. ECK41 RK3506G −25…+85 °C 128 MB; ECK31 T113-S4 −25…+85 °C (board rating) 256 MB, LCSC $21.3; ECK10 MP135 0…70 °C.
  • In-package-DRAM SoCs: RV1106G3 (A7 1.2 GHz + RISC-V MCU, 256 MB DDR3L, 10/100 MAC + PHY, 6 UART, 2 SPI, SDIO, QFN128, TA −20…+85 °C per datasheet V1.9, no CAN, LCSC $8.12); RV1106G2 128 MB; RV1103G1 64 MB $6.85; SSD202D (2×A7 1.2 GHz, 128 MB DDR3, 1 ePHY + 1 RMII, 3 UART + 1 fast UART, 1 SPI master, SDIO 2.0, QFN128, −20…+85 °C per datasheet V0.4, no CAN; datasheet and product brief are public); RK3506G2 (128 MB, −20…+80 °C, 2×CAN, $13.48 @100); T113-S3 (128 MB, −25…+75 °C, $22.3); NUC980DK63YC (ARM926 300 MHz, 64 MB DDR2, LQFP128, 4×CAN, 2×RMII, −40…+85 °C, Nuvoton Direct $9.08 @1–99, $8.47 @500); MA35D1 (2×A35 + M4, up to 512 MB stacked, CAN-FD, 2×GbE, −40…+105 °C, price not obtained).
  • External DRAM does not get cheaper with relaxed temperature: commercial DDR3L is 0 °C minimum.
  • CAN without a native controller: MCP2518FD $1.33–1.75 (E grade), MCP2515 $0.65–1.2, mainline SocketCAN drivers. ESP32-C6 has two TWAI (CAN 2.0) controllers, but carrying CAN on the Wi-Fi coprocessor puts the internet-facing chip on the control bus, makes a C6 reset or OTA drop local CAN control (contradicts design §7), and needs a custom channel beside ESP-Hosted.
  • Rust rewrite: ARMv5 is no longer excluded (armv5te-unknown-linux-gnueabi is tier 2); RV1106 SDK uses uClibc, so build static musl (armv7-unknown-linux-musleabihf, tier 2); ChirpStack is Rust and newer releases support SQLite (Redis dependency unverified), so the 512 MB gate for LR should be recomputed; Zigbee host must be written in-house (EZSP / ZNP).
  • Thermal: a −20…+80 °C part has 5–10 °C margin at 60 °C ambient plus 10–15 °C enclosure rise; RV1106 / SSD202D +85 °C give 5 °C more. −20 °C lower bound misses the family −25 °C.
  • LoRa star: one SX1262 serves many nodes on one channel + SF with a custom MAC. ALOHA fails for 64 Tags at a 2–5 s heartbeat (offered load 66–165 % at SF7/125 kHz); slotted TDMA fits 64 nodes in about 4.6 s at SF7/125 kHz, about 1.5 s at SF7/500 kHz (US DTS). EU868 1 % device duty cycle is exceeded by a 2 s heartbeat at SF7 even under LoRaWAN; 869.4–869.65 MHz allows 10 %. US915 single 125 kHz channel needs hopping or 500 kHz. Saves about $10–18 but loses third-party LoRaWAN devices (GW-08) and needs in-house join, keys, MIC and anti-replay.

Proposal

章节标题：“Proposal”

Revised 2026-09-27 after the owner asked for several hardware combinations, a rewritten hardware specification organised by combination, and an explicit SSD202D + ESP32-C6-as-CAN combination. The spec stops naming one reference platform; it defines platform combinations that share the functional requirements and differ in grade, memory, CAN source and cost. The combination to build is chosen at AIR-O-03.

Platform combinations (base board shared by Air Hub and Air Hub LR; every combination keeps the ESP32-C6 for Wi-Fi). Revised again on 2026-09-27: the owner asked why RK3506G2 was missing and asked for as many combinations as possible, so every candidate from the investigation is a combination, and each SoC without native CAN appears once per CAN source.

ID SoC DRAM CAN source Device grade Note
H1 SSD202D 128 MB in package ESP32-C6 TWAI −20…+85 °C lowest BOM
H2 SSD202D 128 MB in package MCP2518FD on SPI −20…+85 °C
H3 RV1103G1 64 MB in package ESP32-C6 TWAI datasheet check Air Hub only; not LR
H4 RV1106G3 256 MB in package ESP32-C6 TWAI −20…+85 °C
H5 RV1106G3 256 MB in package MCP2518FD on SPI −20…+85 °C
H6 RK3506G2 128 MB in package native −20…+80 °C chip-down or Ebyte ECK41 core board
H7 T113-S3 128 MB in package native −25…+75 °C smallest thermal margin
H8 T113-S4 256 MB in package native chip unverified; ECK31 board −25…+85 °C core board
H9 NUC980 64 / 128 MB in package native 4×CAN −40…+85 °C ARMv5
H10 STM32MP135 external DDR3L native FDCAN −40…+85 °C (grade per suffix) BGA, mainline Linux
H11 T113-i 256 MB+ native −40…+85 °C core board FET113i-S or Ebyte ECK30
H12 RK3506J 256 / 512 MB native −40…+85 °C core board FET3506J-S / -C, MYIR
H13 RK3506J external DDR3L native −40…+85 °C chip-down
H14 MA35D1 up to 512 MB in package native CAN-FD −40…+105 °C price pending

Radio axis (owner, 2026-09-27: "同时包含射频" — combinations include the radio). A complete combination = platform (H1–H14) + functional radio + OOK receiver (LR only).

Air Hub 2.4 GHz functional radio:

ID Radio Images Note
R0 none: the uplink ESP32-C6 also runs BLE (and optionally 802.15.4) BLE, Thread RCP one chip for Wi-Fi + BLE (+ CAN on H1/H3/H4); time-shared radio; Zigbee host immature
R1 EFR32MG21 (+20 dBm) BLE / Zigbee / Thread current recommendation, $3.41
R2 EFR32MG24 BLE / Zigbee / Thread more memory, $8.68
R3 CC2674P10 (or E72 module) BLE / Zigbee / Thread $11.25 / module $7.43
R4 CC2652P7 BLE / Zigbee / Thread Zigbee-first, $3.26
R5 nRF54L15 (+ nRF21540 option) BLE / Thread; Zigbee experimental same vendor as Air
R6 nRF52840 BLE / Thread $3.73
R7 CC2755R10 BLE / Thread if Air goes TI, $5.34
R8 second ESP32-C6 BLE / Thread; Zigbee weak $2.85

Air Hub LR sub-GHz:

ID LoRa OOK Note
L1 SX1302 + 2×SX1250 (LoRaWAN 8 ch) CMT2300A current
L2 SX1303 + 2×SX1250 CMT2300A fine timestamp
L3 Corecell concentrator module CMT2300A certification shortcut, price pending
L4 SX1262 proprietary star (LR-lite) CMT2300A no third-party LoRaWAN
L5 LLCC68 proprietary star CMT2300A SF5–SF11 only
L6 SX1276 single chip: LoRa star + OOK (same chip) one chip, cannot receive both at once
L7 SX1262 star CC1101 or Si4463 OOK alternatives

The spec defines the three axes and their per-option requirements, then a table of named complete combinations spanning cost tiers (Air Hub about 12, Air Hub LR about 8, each with platform + radio + CAN source + grade + capability + BOM range). The full cross-product is not listed; any unlisted pairing is allowed if it satisfies the per-axis requirements.

Files:

  1. Spec P05-air-hub.md R0.7: §1 and §2 rewritten around the combination table (per-combination rows for SoC, DRAM, CAN source, device grade, host-software assumption, capabilities such as local LoRaWAN network server and Matter controller); requirements added for the ESP32-C6 CAN path (C6 forwards only frames issued by Linux over an authenticated internal channel; no Wi-Fi-originated CAN; declared CAN outage on C6 reset or OTA; watchdog) and for the SPI CAN controller; LR-lite as a GW-08 alternative; AIR-O-03 / AIR-O-12 rewritten; Rust host software stated as the assumption behind the 128 MB combinations.
  2. Design P05-air-hub-design.md R0.5: §2 per-combination platform detail and block diagrams, §2.1 SSD202D reason corrected (datasheet V0.4 and product brief are public), ARMv5 / Node.js paragraph rewritten for Rust, §3 roles for the C6-CAN path, §5 interconnect, §7 recovery.
  3. Guide P05-air-hub-guide.md R0.4: quotation and verification per combination (C6-CAN latency and fault tests, thermal test at 60 °C ambient for −20…+85 °C parts).
  4. New evaluation evaluations/low-cost-linux-platform.md: candidate data, sources, per-combination BOM, Ebyte and other core boards, thermal margin, Rust notes.
  5. New evaluation evaluations/lora-star-vs-lorawan.md: capacity, MAC, regional rules.
  6. industrial-linux-and-radio.md: SSD202D row, Ebyte ECK30 rows, pointer to the new page.
  7. Decision docs/decisions/2026-09-27-air-hub-platform-combinations.md: device grade below the family −25 °C for H1–H6 and the +75 °C upper bound of H7, with sunset; index row.
  8. Package index, brief (model capability wording only), product plan row, open questions, docs/changelog.md.

Risks

章节标题：“Risks”
  • Prices are LCSC retail or vendor-store list prices, several with stock of 1; not volume quotes.
  • RV1106 is a vision SoC; Rockchip lifecycle commitment unverified.
  • MA35D1 price and CAN-FD count not obtained; NUC980 128 MB part number not confirmed.
  • H1, H3 and H4 put the internet-facing Wi-Fi chip on the control bus and makes a C6 reset drop local CAN control; the spec must bound this with requirements instead of hiding it.
  • H1–H6 are below the family −25 °C lower bound; H7 is below the +80 °C margin used for 60 °C ambient; needs the decision record.
  • SSD202D price not obtained (no distributor list price found).
  • The Rust rewrite is an owner statement not yet recorded elsewhere; the evaluation states it as an assumption.

Scope

章节标题：“Scope”

Files listed above. Out: Air package, X01 / X02, Tag spec values (Tag heartbeat is flagged under AIR-O-12 only), compliance matrix rows beyond wording.

Outcome

章节标题：“Outcome”

Implemented as proposed with one naming change: the platform evaluation is evaluations/platform-combinations.md (it covers every combination, not only low-cost ones). The named-combination table has 18 Air Hub and 12 Air Hub LR entries. Also updated: the line spec P05-switch.md R0.6, the line index and the compliance matrix v1.3.