Limbo main

Limbo single controller PCB — Rev 2.0

This is the single-board Limbo controller requested for the compact enclosure. It sockets the existing OceanLabz ESP32-S3 DevKit N16R8 and MAX98357A breakout, and provides wired connectors for the OLED, two I2S microphones and speaker. There is no second face PCB.

The design is electrically complete in KiCad, but remains a prototype release, not a production-approved battery product. Measure the exact OceanLabz DevKit, connectors, battery, speaker and enclosure before ordering. See ECO-v2.md for the circuit, parts, power budget and release holds.

What the one PCB contains

• 16-pin USB-C power input with 5.1 kΩ CC resistors, PTC fuse, reverse-current Schottky diode, TVS and CC-line ESD protection.
• BQ24074 single-cell Li-ion/LiPo charger with dynamic power path.
• DW01A + FS8205A cell protection.
• TPS61022 battery-to-5 V boost converter controlled by one latching master switch.
• Socketed ESP32-S3 DevKit and MAX98357A amplifier breakout.
• Two shared-bus I2S microphone connectors, strapped left and right.
• Remote OLED and speaker connectors.
• One buffered WS2812B-Mini addressable RGB status LED.

The master switch disables the boost converter, cutting power to the ESP32, amplifier, OLED, microphones and RGB LED. The charger and battery-protection circuit remain connected so the battery can charge while the product is off.

External connectors

Use short twisted wires for SPK+/SPK−. Keep microphone wiring away from the boost inductor and speaker wiring. The OLED and both microphones are physically mounted in the enclosure, not directly on the PCB.

ESP32 pin map

GPIO19 and GPIO20 remain unused for the DevKit's native USB interface.

Fabrication package

limbo-main-v2.0-fab.zip contains copper, solder mask, silkscreen, board outline and Excellon drill files. Suggested prototype order: two layers, 1.6 mm FR-4, 1 oz copper, HASL or ENIG, green solder mask.

Do not place a production quantity order until every item in the release hold section of ECO-v2.md is closed.

Rebuild and verify

Run from this directory with KiCad 10, OpenJDK 21 and Freerouting 2.1.0:

KIPY=/Applications/KiCad/KiCad.app/Contents/Frameworks/Python.framework/Versions/Current/bin/python3
JAVA21=/opt/homebrew/opt/openjdk@21/bin/java

"$KIPY" gen.py
FREEROUTING__GUI__ENABLED=false \
FREEROUTING__USAGE_AND_DIAGNOSTIC_DATA__DISABLE_ANALYTICS=true \
"$JAVA21" -jar /tmp/freerouting-2.1.0.jar \
  --router.stop_pass_no=40 --router.optimizer.enabled=false \
  -de limbo-main.dsn -do limbo-main-v2-final.ses -mt 1
"$KIPY" apply_ses.py limbo-main.kicad_pcb limbo-main-v2-final.ses
kicad-cli pcb drc --exit-code-violations --severity-all \
  --format json --output drc-limbo-main.json limbo-main.kicad_pcb

gen.py is the authoritative connectivity source for this revision; limbo-main.kicad_pcb is the routed board. A formal KiCad schematic should be captured and reviewed before converting this prototype into a production design.