PCB Layout Design for PCA9685 Servo Controller

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Work done
  • Created and populated the project specification: Project Specification.
  • Renamed the project to Pi Nucleo PCA9685 Servo Controller and set the project description.
  • Added the core schematic parts: 2× PCA9685PW, 1× TXS0102DQER, Raspberry Pi 40-pin header, STM32 Nucleo header, 17 servo headers, 5.1 V and 6.0 V power terminals, 17× 220 Ω PWM series resistors, OE 10 kΩ pull-up, VSENSE divider resistors, and rail/IC capacitors.
  • Verified datasheets: TXS0102 includes internal 10 kΩ pull-ups on A/B I/O pins, so the optional external 4.7 kΩ I2C pull-ups were intentionally not added; PCA9685 OE is active-low, so the 10 kΩ pull-up implements the requested default-disabled servo safety behavior.
Success criteria review
  • ✅ Component set selected and added to schematic.
  • ✅ Datasheet decisions captured for TXS0102 pull-ups and PCA9685 OE/address behavior.
  • ❌ Schematic wiring is not complete yet.
  • ❌ 4-layer stackup, 2 oz copper layout rules, placement, routing, and ERC/DRC validation are not complete.
Next steps
  • Wire all nets: Pi 3.3 V I2C → TXS0102 A-side, TXS0102 B-side → PCA9685 + Nucleo I2C, OE safety net, PCA9685 addresses, 17 PWM resistor chains, servo +6 V/GND rails, decoupling, and VSENSE divider.
  • Then proceed to PCB layout: configure 4-layer/2 oz stackup, size the board, place components, route power/signal nets, and review ERC/DRC.
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Pi Nucleo PCA9685 Servo Controller thumbnail
4-layer dual PCA9685 servo controller for Raspberry Pi 5 and STM32 Nucleo with 20A servo power distribution

Properties

Properties describe core aspects of the project.

Pricing & Availability

Distributor

Qty 1

Arrow

$0.34–$0.46

Digi-Key

$2.50–$3.00

LCSC

$5.19

Mouser

$0.91

Verical

$2.38–$2.66

Controls