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NirlabsScopeLevel
nirinium/nirlabsScopeLevelAn ESP32-based anti-cant level for rifle scopes. Uses an ADXL345 accelerometer to detect tilt and provides real-time LED feedback so you know when your rifle is level before taking a shot.
- Size
- 50 × 30 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 21
- Nets
- 17
- Pads
- 54
- Tracks, vias
- 0, 0
- Routed
- Not yet
- KiCad
- KiCad 7.0 (file 20231120)
- Created
- 20 Apr 2026
- Updated
- 2 May 2026
Overview
NirlabsScopeLevel is an open-source printed circuit board by nirinium, from the nirinium/nirlabsScopeLevel repository on GitHub. It is a 2-layer board of 50 × 30 mm with 21 parts on 17 nets.
It is built around the XIAO ESP32C3. Its parts include 7 resistors, 5 diodes, 2 ICs, 1 capacitor and 1 connector. It belongs with the ESP32 and RISC-V boards of this library.
Main components
1README
README.mdnirlabs Scope Level
An ESP32-based anti-cant level for rifle scopes. Uses an ADXL345 accelerometer to detect tilt and provides real-time LED feedback so you know when your rifle is level before taking a shot.
Features
- Three-zone indication — Level (green), Near-level (green fade + red flash), and Cant (red heartbeat double-pulse)
- Directional feedback — Left or right red LED indicates which way you're canted
- Hysteresis — Prevents flickering at zone boundaries
- EMA filtering — Exponential moving average smooths sensor noise
- Auto-calibration — Calibrates on boot assuming the device is held level
- Battery monitoring — Low-battery warning via red LED double-blink every 5 seconds
- Power management — Enters light sleep after 1 minute at level to conserve battery
Hardware
| Component | Pin |
|---|---|
| Green LED | GPIO 25 |
| Red LED (Left) | GPIO 26 |
| Red LED (Right) | GPIO 27 |
| Battery voltage divider | GPIO 34 (ADC) |
| ADXL345 SDA | GPIO 21 |
| ADXL345 SCL | GPIO 22 |
Board: NodeMCU-32S (ESP32)
Zone Thresholds
| Zone | Range |
|---|---|
| Level (green solid) | < 0.5° |
| Near level (green fade + red pulse) | 0.5° – 1.5° |
| Cant (red heartbeat) | > 1.5° |
Build
This project uses PlatformIO.
# Build
pio run
# Upload
pio run --target upload
# Serial monitor
pio device monitorDependencies
Adafruit Unified Sensor^1.1.15Adafruit ADXL345^1.3.4
Configuration
Key constants in src/main.cpp:
| Constant | Default | Description |
|---|---|---|
THRESHOLD | 0.5° | Dead-level zone boundary |
NEAR_ZONE | 1.5° | Near-level to cant boundary |
MAX_CANT | 5.0° | Maximum urgency angle |
HYSTERESIS | 0.15° | Zone boundary flicker prevention |
EMA_ALPHA | 0.4 | Filter smoothing (lower = smoother) |
SLEEP_TIMEOUT | 60000 ms | Idle time before light sleep |
BATT_LOW | 3.3 V | Low battery warning threshold |
DEBUG_MODE | true | Serial debug output (set false for production) |
License
NIRINIUM|LABS
Parts
21| Qty | Value | Footprint | References |
|---|---|---|---|
| 5 | 100R | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | R1, R2, R3, R4, R5 |
| 4 | MH_3.2mm | MountingHole:MountingHole_3.2mm_M3 | MH1, MH2, MH3, MH4 |
| 2 | 100k | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal | R6, R7 |
| 1 | 100nF | Capacitor_THT:C_Disc_D3.0mm_W1.6mm_P2.50mm | C1 |
| 1 | ADXL345_Breakout | Connector_PinHeader_2.54mm:PinHeader_1x06_P2.54mm_Vertical | U2 |
| 1 | LED_GREEN | LED_THT:LED_D3.0mm | D1 |
| 1 | LED_RED_L | LED_THT:LED_D3.0mm | D3 |
| 1 | LED_RED_R | LED_THT:LED_D3.0mm | D5 |
| 1 | LED_YEL_L | LED_THT:LED_D3.0mm | D2 |
| 1 | LED_YEL_R | LED_THT:LED_D3.0mm | D4 |
| 1 | LiPo_JST_PH | Connector_JST:JST_PH_S2B-PH-K_1x02_P2.00mm_Horizontal | J1 |
| 1 | Power_Slide_SW | Button_Switch_THT:SW_Slide_1P2T_CK_OS102011MA1QN1 | SW1 |
| 1 | XIAO_ESP32C3 | Seeed_XIAO:XIAO_ESP32C3 | U1 |
Questions
How big is the NirlabsScopeLevel PCB?
It measures 50 × 30 mm and has 2 copper layers, 1.6 mm thick.
What parts does the NirlabsScopeLevel use?
21 parts, built around the XIAO ESP32C3. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the NirlabsScopeLevel KiCad files?
From the nirinium/nirlabsScopeLevel repository on GitHub, at the commit this page was made from: the board is kicad/nirlabs_scope_level.kicad_pcb and its schematic kicad/nirlabs_scope_level.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the NirlabsScopeLevel design in my own project?
Its repository states no licence, so its author keeps all rights: ask nirinium before reusing the design.
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