GPIO header reference, KiCad templates, mechanical envelope, sample DIY projects, PCB-from-scratch checklist

Section	Topic
1	About this Volume
2	The Header — KiCad / EDA-side reference
· 2.1	The connector spec
· 2.2	KiCad and Eagle libraries
· 2.3	The mechanical envelope
· 2.4	Cases — printable
3	Pin-Budget and Routing Discipline
· 3.1	Three rules that prevent most DIY pain
· 3.2	Power
· 3.3	Signal levels
4	Sample DIY Projects
· 4.1	DIY ESP32-C6 / S3 Daughterboard
· 4.2	DIY NRF24 board on a perfboard
· 4.3	DIY IR-blaster boost stage
· 4.4	DIY GPS module
· 4.5	DIY Environmental Sensor Pack
· 4.6	DIY OBD-II carrier (ELM327 + level shift)
· 4.7	DIY Audio I²S DAC
· 4.8	Pin-extender / breakout headers
5	Reference Open-Hardware Projects
6	The PCB-from-Scratch Checklist (tjscientist’s lab edition)
· 6.1	Spec phase
· 6.2	Schematic phase
· 6.3	Layout phase
· 6.4	Fab + assembly
· 6.5	Bring-up
7	Common DIY-Specific Pitfalls
8	The 3V3 Rail Watchdog Pattern
9	PCB Tools That Are Worth Knowing
10	What’s next

1. About this Volume

When the right module doesn’t exist commercially — or when you want a specific feature combination at a lower BOM cost than buying — DIY is the answer. tjscientist’s lab (full PCB fab + small-scale assembly) makes this trivial cost-wise; the hard part is getting the GPIO mapping, mechanical envelope, and Flipper-side firmware integration right. This volume covers all three.

2. The Header — KiCad / EDA-side reference

2.1 The connector spec

The Flipper’s GPIO header is a 2×9 (18-pin) 1.27 mm pitch female header on the device side. The matching male connector on a daughter PCB is 2×9 1.27 mm pitch. Most modules use a press-fit header for tool- free attach/detach.

Vendors and part numbers:

Part	Function	Vendor / LCSC
Standard 2×9 1.27 mm header (male)	Daughter PCB → Flipper	Multiple; LCSC C155829 (generic)
2×9 1.27 mm SMD header (low profile)	Same, lower stack height	LCSC C496497
2×9 1.27 mm right-angle	Daughter PCB exits horizontally	LCSC C492447

The press-fit fitting on the Flipper side wears with insertion cycles — not a serious concern under 100 mate cycles, becoming noticeable past ~500. Treat it as semi-permanent.

2.2 KiCad and Eagle libraries

Two open libraries cover the connector + Flipper outline:

kbembedded/flipper-gpio-eda — KiCad and Eagle symbol/footprint libraries for the Flipper GPIO connector. Use this rather than re-drawing the part. Pairs cleanly with KiCad 7+.
lomalkin/flipperzero-protoboards-kicad — KiCad protoboards designed against the published GPIO pinout. The canonical starter for any DIY GPIO board. Open license, uses the community’s reverse-engineered footprint.

Drop either library into your *.lib/*.kicad_sym includes; the connector symbol exposes net names matching the docs.flipper.net pinout table (Vol 7 §2).

2.3 The mechanical envelope

The “mechanical envelope” is the volume above the Flipper’s top edge where a module can extend without hitting the Flipper’s body or buttons. Approximate dimensions (verify against your specific device):

Width:    ~76 mm (Flipper body width, no fenders)
Depth:    ~20-25 mm (module depth above the GPIO header — varies)
Height:   ~30-40 mm of usable Z above the header before mechanical
          interference with Flipper button cluster

Above ~40 mm Z is fine - just ensure the module doesn't overhang
back-side away from the Flipper body more than ~5 mm without support
(prevents snap-off in pocket).

The community mechanical envelope spec is documented at flipper.wiki hardware-overview and in the 3D models repo (flipperdevices/flipperzero-3d-models). 3D-print the Flipper body STL and lay your daughter PCB on top to verify fit before fabricating.

2.4 Cases — printable

MuddledBox/FlipperZeroCases — Apache-licensed STLs for hard covers including “GPIO covered” and “GPIO open” variants.
fivesixzero “Case for Flipper Zero Wi-Fi Module v1” — Printables.com #179910, the cleanest open-license case for the ESP32-S2 devboard footprint. Useful as a baseline shell to extend.
TruTech / fivesixzero forks on Printables for module-specific shells (Mayhem, Game Over, etc.).

3. Pin-Budget and Routing Discipline

3.1 Three rules that prevent most DIY pain

Don’t draw more than ~150 mA continuous from the 3V3 rail. Multi-radio designs need their own boost converter or USB-C input.
Tie unused GPIO pins to ground or pull them high through 10–100 kΩ pull-up resistors. Floating MCU inputs draw irregular current and pick up noise. The Flipper firmware doesn’t drive every pin every cycle; treat the header as if pins might be high-Z.
Use the 1-Wire pin (17) for low-frequency single-bit signals only. It’s electrically connected to the iButton pad and to the firmware’s 1-Wire master — collision is at best annoying, at worst destructive.

3.2 Power

If your module needs > 50 mA, take it from the 5 V GPIO pin (1) with a buck regulator down to your needed voltage, rather than from 3V3. The 5 V rail off USB has plenty of headroom; the boost from battery is weaker but still better than the 3V3 sub-rail.

If your module must run on the 3V3 rail directly (small sensors, discrete radios), use a soft-start cap (10 µF + 0.1 µF on the input) to absorb inrush.

3.3 Signal levels

All Flipper I/O is 3.3 V tolerant only. Level-shift externally if your slave runs at 5 V. Common shifters:

74LVC1T45 — single-channel bi-directional, auto-direction. Tiny.
TXB0104 / TXB0108 — 4 / 8 channel, auto-direction.
MOSFET pair (BSS138 + 10 kΩ + 10 kΩ) — discrete, slow but cheap.

For UART → 5 V TTL, the 74LVC1T45 chain is what most ESP32 daughterboards use. For I²C → 5 V, the BSS138 chain is the reference. Don’t try to direct-connect a 5 V part to the Flipper — even a 50-pin signal swing above 3.6 V can stress the MCU clamp diodes over time.

4. Sample DIY Projects

4.1 DIY ESP32-C6 / S3 Daughterboard

The official WiFi Devboard is stuck on ESP32-S2 (no BLE 5, no Thread/ Matter, no 802.15.4). DIY route:

KiCad: drop a Seeed XIAO ESP32-C6 (or ESP32-S3) onto a lomalkin protoboard.
Wire UART: ESP32 RX → Flipper pin 13 (TX, PB6). ESP32 TX → Flipper pin 14 (RX, PB7). GND, 3V3.
Add a USB-C connector for direct flashing + standalone power.
Drop a BOOT/RESET button pair for ESP32 flashing in case the Flipper-side flasher fails.
Flash FlipperHTTP (jblanked’s repo supports C5/C6/S3) or Marauder-fork-with-BLE5 for BLE 5 attacks.

Total BOM: $5–8 ESP32 dev module + $0.50 USB-C + $0.20 buttons + $1 header + $2 PCB. Under $15 turnkey.

The Apex 5 (Vol 9 §2.4) is the closest commercial answer with ESP32-C5; the DIY route is cheaper and customizable.

4.2 DIY NRF24 board on a perfboard

NRF24L01+ on bare 5-pin SPI is ~$3 from Aliexpress. Drop one on a perfboard, wire to GPIO pins per Vol 8 §4.3, slap it in a 3D-printed shell. 30 minutes start to finish.

For longer range, get the “NRF24L01+ Long Range PA+LNA” variant with SMA antenna (~$8). 100 m+ MouseJack range.

4.3 DIY IR-blaster boost stage

A higher-power IR transmitter for 30+ ft range:

        +5V GPIO (pin 1)
            │
            ├─── 220 µF cap (buffer)
            │
   ┌────────┤
   │        │
   ▼        │
  IR LED    │  3 in series
  IR LED    │  (940 nm, e.g. Everlight IR333C)
  IR LED    │
   │        │
   ├────────┘
   │
   ▼  10 Ω 1 W  (current limit; calc: (5V - 3*1.5V) / 10 = 50 mA peak)
   │
   ▼
  BC337 / 2N3904 NPN
   │   collector
   │
   ── BASE: 1 kΩ → Flipper PA7 (pin 2, output via TIM PWM, carrier 38 kHz)
   │
   ▼
  GND

Wire to Flipper pin 2 (PA7) via the 1 kΩ base resistor. Configure Unleashed/Xtreme/RogueMaster IR app → External GPIO → Send=A7. Done. Range jumps from 5 m to ~30+ ft.

Refine with a high-gain LED (Vishay TSAL6100, 80 mW/sr) and the range goes another 2–3×.

4.4 DIY GPS module

Buy a $5 NEO-6M from Aliexpress. Wire:

NEO-6M VCC → Flipper 3V3 (pin 9)
NEO-6M GND → Flipper GND (pin 8 or 11 or 18)
NEO-6M TX  → Flipper RX (pin 14, PB7)
NEO-6M RX  → Flipper TX (pin 13, PB6) [optional; for AT commands]

3D print a small case that clips above the GPIO header. Install ezod/flipperzero-gps FAP. ~$5 turnkey GPS.

4.5 DIY Environmental Sensor Pack

I²C is on pins 15 (SDA, PC1) and 16 (SCL, PC0). Drop:

BME280 — temperature, humidity, pressure (~$3, 0x76 or 0x77)
BMP680 — gas + IAQ (~$8, 0x76 or 0x77)
MH-Z19B — CO2 (~$25, UART or PWM)
VEML7700 — ambient light (~$3, 0x10)

All on the same I²C bus (different addresses). FAPs:

quen0n/unitemp-flipperzero for BMP/BME/HTU/DHT/DS18B20
kamylwnb/bme680_flipper_zero for BME680
DIY MicroFAP for MH-Z19 (UART) — straight read of CO2 every 5 sec

Total kit BOM under $40 for a four-sensor pack.

4.6 DIY OBD-II carrier (ELM327 + level shift)

Wire an ELM327 module’s UART to Flipper UART through a 5 V → 3.3 V level shifter. Connect the OBD-II side to vehicle. Custom FAP queries ELM327 ATZ/ATSP6/0100, decodes responses. Useful for read-only vehicle diagnostics from the Flipper UI.

Variant: bare CAN transceiver (MCP2515 + MCP2562) on SPI. Read raw CAN frames. Substantially more useful for protocol RE work.

4.7 DIY Audio I²S DAC

The Flipper has no audio DAC, but DIY one:

PCM5102 I²S DAC module (~$5)
Bit-bang I²S on three GPIO pins: BCK (bit clock), LRCK (left/right clock), DATA. Use timer-driven IRQ to clock samples at 44.1 kHz.

Performance: limited by how fast the firmware can shovel samples. Quality depends on FAP — typical I²S-bit-bang on STM32WB55 reaches 22 kHz / 8-bit PCM comfortably; 44.1 / 16-bit needs DMA + timer help that’s harder to get right from a FAP. Easier path: use a UART-driven I²S DAC like the Maxim MAX98357 — accepts a serial bitstream rather than I²S clocks.

4.8 Pin-extender / breakout headers

The simplest DIY: a 2×9 1.27 mm header on top, a 2×9 1.27 mm header on bottom, all 18 pins straight through. Lets you use the Flipper GPIO with jumper wires while a “real” module also stacks on top. Sometimes called a “pin-passthrough adapter”.

5. Reference Open-Hardware Projects

These are existing open designs to study, not necessarily build:

zst123/FCFZ — “Fully Compatible Flipper Zero” on Hackster.io. Open hardware that mimics the Flipper pinout. Useful for understanding what GPIO behaviors the Flipper firmware actually expects from a module.
GthiN89/FuckingCheapFlipperZero — Hackaday.io #203021. Off-the- shelf-module DIY Flipper alternative running Momentum, ~€10–30 BOM. Good schematic/firmware reference.
UberGuidoZ/Flipper — the GPIO/ folder is the largest community pinout/wiring reference: ESP32, ESP8266, ESP32-CAM, NRF24, plus DSTIKE Deauther wiring. The de-facto map.
Hackaday’s flipper-zero tag — a steady drip of one-off DIY boards: AS7331 UV (full custom I²C library), CAN-bus shields, low-power FM transmitters, hall-effect probes, LoRaWAN nodes. Use as starter templates.
Lab401 LightMessenger — POV-stick LED column on the GPIO header. Open design. A worked example of “trivial GPIO + clever FAP = real product”.

6. The PCB-from-Scratch Checklist (tjscientist’s lab edition)

Tailored to the lab tjscientist has on the bench. Each step has a deliverable.

6.1 Spec phase

Block diagram: every IC, every connector, every power rail.
Power budget: peak + continuous current per rail. Numbers, not “should be fine”.
GPIO assignment table: which Flipper pin does what. Reserve unused pins as “FUTURE” with explicit pull state.
Mechanical sketch: bounding box, connector placements, height envelope. Verify against flipperzero-3d-models.

6.2 Schematic phase

Schematic in KiCad using the kbembedded/flipper-gpio-eda symbol library. Power flags on every rail.
Decoupling: 0.1 µF + 1 µF on every IC’s VDD pin.
Level shifters wherever a 5 V signal meets the Flipper.
Test points on every signal you might want to scope post-fab. At least: each rail, UART RX/TX, SPI MOSI/MISO/SCK, any clock.
ESD protection on user-facing connectors (USB, antenna SMA).

6.3 Layout phase

2-layer for simple cards, 4-layer for radio/multi-radio.
Ground plane on bottom (2L) or layer 2 + 3 (4L).
Crystal placement: as close to the IC as possible, with stitch vias around the trace pair.
Antenna routing: 50 Ω controlled-impedance microstrip (for 4-layer 0.8 mm with FR4, that’s ~0.36 mm wide). Keep ≥ 5 mm from any noisy switching node.
3D check — load the STEP into FreeCAD, verify the connector doesn’t fight the Flipper edge.
DRC clean before sending to fab. Don’t assume the fab catches it; it doesn’t.

6.4 Fab + assembly

JLCPCB / PCBWay spec: 4-layer, 0.8 mm, ENIG, edge bevel if you want a clean USB-C insert.
Stencil if reflowing — 0.1 mm thick laser-cut.
Reflow profile matched to your paste (typically Sn63Pb37 lead if you’re doing rework, SAC305 if you’re going production-style).
First-article test: power up at 0.5 A current limit on bench supply. If the supply hits limit, it’s a short — power off immediately, troubleshoot. Don’t assume.

6.5 Bring-up

Power rails verified with multimeter on each test point.
MCU enumerated via SWD before exercising the Flipper.
Each subsystem tested independently before integration. Don’t debug 3 things at once.
Flipper-side FAP written to exercise each signal. Don’t expect the production FAP to “just work” — the simple test FAP isolates hardware bugs from firmware bugs.

7. Common DIY-Specific Pitfalls

Pitfall	Symptom	Fix
Running 5 V signal into Flipper GPIO	MCU clamp diodes degrade; Flipper resets eventually	Always level-shift
Drawing > 150 mA from 3V3	Flipper resets during module activity	External power for high-current modules
Forgetting to GND-bond unused GPIO	Floating pins pick up noise; readings flap	Pull down (or up) every unused pin
Wrong-polarity connector	Module doesn’t power up; possibly damages IC	Match the 18-pin pinout exactly; verify with a probe before powering
Inserting NRF24/CC1101 daughterboard backwards (in modules with a sub-slot)	Magic smoke from one or both	Key the slot in your design; never trust orientation
Multi-radio TX during HDMI streaming on VGM-stack	Wi-Fi/Sub-GHz TX power 6-10 dB lower	Schedule TX to not overlap HDMI active
Forgetting the 1.27 mm pitch	Fabbed PCB doesn’t mate with Flipper	KiCad library has the right pitch — use it
Not testing in pre-production	Catch a layout bug at production scale	Always order a 2-board prototype first

8. The 3V3 Rail Watchdog Pattern

For DIY designs that absolutely must run on the 3V3 rail (no external USB), add a watchdog:

3V3 IN ──┬──── To module
         │
         ▼
        100 mΩ shunt resistor
         │
         ▼
  ADC pin (e.g. PC0 / pin 16) on the Flipper, sampled
  by your FAP at 100 Hz. If voltage across the shunt
  exceeds 15 mV (= 150 mA), throttle module activity.

Software cheap, hardware cheap, prevents brown-outs on edge-case TX profiles. None of the commercial multi-radio modules do this — you can.

9. PCB Tools That Are Worth Knowing

For tjscientist’s lab specifically (he has the equipment):

KiCad 7+ for schematic + layout. Free, open. The community standard.
DipTrace or Eagle if you’ve already got muscle memory.
FreeCAD for STEP-level mechanical verification. Import the Flipper’s STEP from flipperzero-3d-models.
JLCPCB / PCBWay for fab. JLCPCB cheaper, 4-layer 0.8 mm at $20 for 5 boards; turnaround 7–10 days incl. shipping.
Stencil from JLCPCB as part of the same order; good quality.
For assembly: hand-paste with a manual stencil + reflow oven works well at 5–10 board volumes. JLCPCB SMT service is worth it past 20 boards.

10. What’s next

Vol 11 — Workflows & Recipes. End-to-end field workflows: garage-door analysis, RFID badge audit, BLE keyboard pentest, NFC tag programming, ham/SDR companion-mode with HackRF/RTL-SDR, qFlipper + Mobile App workflows.

Flipper Zero Volume 10 — DIY Modules

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