libdrone Core — Platform Specification
About¶
Specification for libdrone Core — the 4-inch educational variant. Shares structural philosophy, key components, and software stack with libdrone Pro while optimised for affordability, build accessibility, and teaching. Primary purpose: FPV piloting education, drone construction teaching, and ecosystem demonstration.
libdrone Core — Platform Specification¶
Version: 1.0 Date: 2026-03-17 Licence: CERN OHL-S v2
1. What is libdrone Core¶
libdrone Core is the 4" educational variant of the libdrone platform. It shares the structural philosophy, key components, and software stack with libdrone Pro, while being optimised for affordability, build accessibility, and teaching.
Primary purpose: - Teaching FPV piloting - Teaching drone construction (soldering, 3D printing, Betaflight, ELRS) - Promo and demo platform for the libdrone ecosystem
Core is not: - A replacement for the Pro variant - A payload-capable platform - An NDAA/EU compliance product (at this stage)
2. Relationship to libdrone Pro¶
| Aspect | Pro | Core |
|---|---|---|
| Prop size | 6" | 4" |
| Power | 6S XT60 | 4S XT30 |
| FC | Matek H7A3-SLIM | ← shared |
| ESC | SpeedyBee/Pilotix | SpeedyBee BLS 50A 30×30 |
| Motors | 2507 1750KV | T-Motor Pacer 1804 3400KV |
| ELRS RX | Happymodel EP2 Nano | ← shared |
| CF rods | 3 mm | ← shared diameter |
| Video | HDZero digital | Analog (Foxeer) |
| Print material | PC-CF | PETG |
| Payload interface | Dual GX12-7 A/B | Dual GX12-7 A/B — mandatory |
| Purpose | Research, commercial | Education, promo |
Shared SKUs minimise stock requirements and simplify documentation maintenance.
3. Technical Specifications¶
| Parameter | Value | Note |
|---|---|---|
| Configuration | True-X | |
| Prop size | 4" | |
| Wheelbase | ~160 mm | derived from prop size |
| FC stack mount | 30×30 mm | Matek H7A3-SLIM |
| Power system | 4S | 14.8 V nominal |
| Battery connector | XT30 | |
| Max take-off weight | TBD after first build | |
| CF rod diameter | 3 mm | shared with Pro |
| Print material | PETG |
4. Bill of Materials¶
4.1 Electronics¶
| Component | Model | Note |
|---|---|---|
| Flight Controller | Matek H7A3-SLIM | STM32H7A3, shared with Pro |
| ESC | SpeedyBee BLS 50A 30×30 4in1 | 3–6S, TDK caps, TVS diode, large pads |
| Motors | T-Motor Pacer P1804 3400KV | NMB bearings, titanium shaft, 4S |
| ELRS Receiver | Happymodel EP2 Nano | 2.4 GHz, shared with Pro |
| Camera | Foxeer Predator Nano | Taiwan, WDR |
| VTX | Foxeer Reaper Nano V2 | Taiwan, 350 mW, IRC Tramp |
4.2 Mechanical¶
| Component | Specification |
|---|---|
| CF rods | 3 mm diameter, length per CadQuery Core parameters |
| Printed parts | PETG, all parts from CadQuery generator (Core profile) |
| Propellers | GemFan 4024 tri-blade, Taiwan |
4.3 Power¶
| Component | Specification |
|---|---|
| Battery | 4S 850 mAh XT30 |
| Connector | XT30 |
5. Video System¶
Core uses analog video — intentionally, for cost and goggle availability in educational contexts.
Operator (Jakub): - HDZero Goggle 2 — built-in analog receiver, no extra module required - Foxeer Predator Nano + Reaper Nano V2 = fully operational out of the box
Students: - Standard box goggles (Eachine EV800D or equivalent) - Goggle selection is not part of the Core BOM — depends on deployment context
6. Control System¶
| Hardware | Status |
|---|---|
| RadioMaster TX16S | ✓ compatible, ELRS 2.4 GHz |
| RadioMaster Pocket ELRS | Recommended for students (same ecosystem) |
| Any ELRS 2.4 GHz controller | ✓ compatible |
Binding procedure identical to Pro variant.
7. Software Stack¶
Core shares the software stack with Pro:
| Software | Status |
|---|---|
| Betaflight | ✓ full compatibility, same FC |
| MSP pre-flight checker (Python) | ✓ works on Core without modification |
| EdgeTX Lua widget (TX16S) | ✓ works on Core without modification |
| CadQuery parametric generator | Extension planned, Core profile TBD |
8. Structure and 3D Printing¶
Core shares the CF rods + 3D print structural philosophy with Pro. Key differences:
- PETG instead of PC-CF: lower printer requirements, available in school environments, sufficient strength for 4" / 4S
- Dual GX12-7 payload interface: both Connector A and B fitted and wired — identical to Pro. A payload built on Core flies on Pro without modification. This is the entire point of a platform standard. Students learn the real interface from day one.
- Pi bay: always printed, always present — identical 6mm PETG tray above Backplane. Companion harness (UART6) pre-wired during build. Pi Zero 2W optional (LCM-1).
- 30×30 stack: smaller than Pro, hub geometry adjusted accordingly
- All parts printable on Prusa MK4 or equivalent
The CadQuery generator will be extended with a Core profile (Pro/Core switch in parameters).
9. Intended Deployments¶
| Context | Configuration |
|---|---|
| Promo / demo (Jakub) | HDZero Goggle 2 + TX16S |
| Lab teaching | Shared box goggles + RadioMaster Pocket ELRS |
| Telč Skatepark (September 2026) | Demo flight, platform documentation |
10. Project Status¶
| Milestone | Status |
|---|---|
| Specification and BOM | ✓ Complete |
| Shopping list | ✓ Complete (libdrone-core-shopping-list.md) |
| Component order | Planned April 2026 |
| CadQuery Core profile | TBD |
| First build | TBD after component delivery |
| Promo flight / photography | TBD after build |
| Telč Skatepark flight | Target September 2026 |
This document is part of the libdrone documentation stack. Numeric values shared across the platform are authoritatively stored in the Variables file.
Revision History¶
| Version | Date | Author | Summary |
|---|---|---|---|
| 0.2 | 2026-03-29 | JS | Dual GX12-7 mandate added (both connectors, fully wired). Pi bay added. "No payload interface" language removed. Payload interface now identical to Pro. |
| 0.1 | 2026-03-17 | JS | Initial Core specification. |