Dual Servo Controller PCB Design

flux

Work done
  • Built the dual-PCA9685 schematic with Raspberry Pi 5 I²C input, STM32/Nucleo control header, TXS0102 3.3V↔5.1V translation, 5.1V logic rail, 6.0V servo rail, 17 servo outputs, 220Ω series resistors, and OE pull-up fail-safe.
  • Configured U1 at I²C address 0x40 and U2 at 0x41, renamed the Pi-side TXS0102 rail to 3V3_PI, and added no-connect markers for intentionally unused pins.
  • Set up a 120mm × 100mm 4-layer PCB with an inner ground plane and inner power plane, placed all 52 real components, and added high-current layout metadata/rules for the 20A 6V_SERVO rail.
  • Updated Design Notes with datasheet confirmations, layout constraints, and validation status.
Success criteria review
  • ✅ Dual PCA9685 schematic, addressing, OE safety pull-up, I²C translation, common GND, power rails, and 17 protected servo PWM outputs are implemented.
  • ✅ PCB stackup and placement are configured for a 4-layer high-current board concept.
  • ✅ ERC is clean after marking intentionally unused pins.
  • ⚠️ Full DRC clearance is not complete: 84 airwires remain because physical routing/copper pours still need to be completed.
  • ⚠️ The stackup records the 2 oz copper requirement in project metadata/design notes, but the visible stackup template still shows default 0.035mm copper thickness; confirm the final fab stackup/copper weight with the board manufacturer.
Next steps
Complete PCB routing/pours for GND, 6V_SERVO, 5V1_LOGIC, I²C, OE, VSENSE, and PWM outputs, then re-run DRC until airwires are cleared before manufacturing export.
Route power first
Group DRC airwires
Set 2 oz stackup
Verify connector ratings
Prepare exports
Sign up to send
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Dual PCA9685 Servo Controller thumbnail
4-layer dual PCA9685 servo controller with Raspberry Pi 5, STM32 Nucleo, TXS0102 I2C level shifting, 6.0V/20A servo rail, and 5.1V logic rail.

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