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* Fix JST 3D model in lib, add wrl, re-render board images Same fix as OpenESC-30x30: the JST SM08B footprint's STEP model rendered the housing on stilts past the board edge. Replaced with the proven VRML model from OpenFC-Lite at offset (-3.5, 2.17, 0), derived from the pad geometry and verified by render. The J1 board-instance fix is in the working tree mixed with uncommitted layout and schematic work and will be committed with it; renders reflect that current state, verified IC by IC on both sides. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * chore: point every GitHub link at OpenDrone-hw The org was renamed from incutec-hw to OpenDrone-hw. Old links only work through GitHub's rename redirect, which stops working as soon as the incutec-hw name is registered again for the company org. Docs and submodule URLs only. No design files touched. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> --------- Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
76 lines
4.7 KiB
Markdown
76 lines
4.7 KiB
Markdown
# OpenESC-20x20 Design Notes
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Detailed design description of the OpenESC-20x20. Values are extracted from the KiCad design files: `hardware/4in1-mini.kicad_sch`, `hardware/ESC.kicad_sch`, `hardware/4in1-mini.kicad_pcb`.
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## Architecture
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Four fully independent ESC channels share a common power input and telemetry connector. Each channel has its own MCU and gate driver; the high-current stage is six MOSFETs per channel (three half-bridges). This is the distributed-MCU AM32 topology rather than a single-MCU design.
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| Block | Part | LCSC | Per board |
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| Motor MCU | AT32F421G8U7 (QFN-28) | C2765098 | 4 |
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| Gate driver | NSG2065Q (QFN-24) | C41414478 | 4 |
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| Power MOSFETs | DOY180N03T PowerDI3333-8 | C49441966 | 24 (6 per channel) |
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## Full specifications
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| Parameter | Value |
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| Channels | 4 independent BLDC channels |
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| MCU | AT32F421G8U7 (ARM Cortex-M4, QFN-28), one per channel |
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| Gate driver | NSG2065Q (QFN-24, FD6288Q-compatible), one per channel |
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| Power MOSFETs | DOY180N03T, N-channel, 30 V, PowerDI3333-8, 24 total |
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| Current sense | Board-level high-side: INA186A3IDCKR (100 V/V, SC-70-6) across 1x 0.2 mOhm 2512 shunt in the +BATT feed, 20 mV/A, 165 A full-scale at 3.3 V ADC |
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| Input | +BATT direct from connector/pads, 6S |
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| Input protection | 2x SMF24A-T13 TVS (24 V standoff) |
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| Buck regulator | LMR54406DBVR (SOT-23-6) + FTC160808S4R7MBCA 4.7 uH inductor, produces the +10 V gate-drive rail (FB 115k/10k, Vref 0.8 V, 10.0 V out) |
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| LDO | TLV76733DRVR (WSON-6), +10 V in, +3V3 out (MCUs, sensing) |
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| Signal protocol | DShot (4 independent signal lines, one per channel) |
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| Firmware | AM32 (per-channel AT32F421 target, flashed individually) |
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| PCB | 6-layer, 1.69 mm, outline approx. 31.3 x 33.1 mm |
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| Mounting pattern | 20 x 20 mm, 4x 3.0 mm holes (M2 hardware with grommets) |
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The board is 6S only: the input clamp is set by the SMF24A-T13 TVS (24 V standoff). Current and voltage ratings are not printed in the design files; the MOSFET (DOY180N03T) and current-sense full-scale (165 A) bound the practical envelope. Characterize before quoting a hard rating.
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## Power tree
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+BATT (6S) feeds the MOSFET drains directly, the current shunt, and the LMR54406DBVR buck. The buck produces +10 V for the four gate drivers; the TLV76733DRVR LDO drops +10 V to +3V3 for the four MCUs and the current-sense amplifier. Input clamp: 2x SMF24A-T13 TVS.
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## Connector
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8-pin JST **SM08B-SRSS-TB** (J1). Pin-to-net mapping extracted from the schematic (net labels at the connector pins):
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| Pin | Net | Function |
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| 1 | +BATT | Battery positive |
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| 2 | GND | Ground |
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| 3 | /CURR | Current-sense telemetry (INA186 output) |
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| 4 | *(unconnected)* | No dedicated telemetry pin, telemetry handled by extended DShot |
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| 5 | /M1 | DShot signal, channel 1 |
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| 6 | /M2 | DShot signal, channel 2 |
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| 7 | /M3 | DShot signal, channel 3 |
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| 8 | /M4 | DShot signal, channel 4 |
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Connector ground returns on the shield/mounting pads P1/P2 (both GND). Pin 4, the dedicated telemetry pin on the Betaflight 8-pin standard, is intentionally unconnected: ESC to FC telemetry is carried over the motor signal lines via the bidirectional **extended DShot** protocol.
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## Variants and revisions
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This repo is the 20x20 member of the OpenESC family. A larger sibling, [OpenESC-30x30](https://github.com/OpenDrone-hw/OpenESC-30x30) (30.5 x 30.5 mm), shares this design and mirrors this repo; the two differ only in board/mounting size and a few power-stage parts. Fabrication export procedure: see [Manufacturing](../../README.md#manufacturing).
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## QC fixture
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`20x20-ESC-QC/` is a separate KiCad 10 project: a press-contact fixture whose board is a negative of the ESC contact face, used for functional and current-transfer tests without soldering leads. See [20x20-ESC-QC/README.md](../../20x20-ESC-QC/README.md).
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## Firmware
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[AM32](https://github.com/am32-firmware/AM32) is incutec's default ESC firmware. Boards ship with the AM32 bootloader pre-loaded; firmware is flashed and configured in-browser at [am32.ca](https://am32.ca). Production flashing: see [Manufacturing](../../README.md#manufacturing). Each channel's AT32F421G8U7 is an independent AM32 target. The AT32F421 + NSG2065Q per-channel topology and the DShot signal nets are the standard AM32 hardware target for this board class. Works with Betaflight and other DShot-capable flight controllers.
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## Revisions
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- **Rev2-20x20** (2026-06-05): validated build, current production export set.
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- **V2** (2026-05-04): export `V2`.
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- **V1** (2026-03-18): export `V1`; a NextPCB variant export (`V1_nextpcb`) preceded it on 2026-03-14.
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- **v0.3** (2025-11-13): export `v0.3`.
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- **v0.2** (2025-11-13): export `v0.2`.
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- **v0.1** (2025-11-10): first production export.
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