4-Layer PCB Design for Servo Controller

flux

1:03

Thought for 2 sec

Created 4 tasks.

1/4 Inspect U3 and R19 current parts, values, pins, and connectivity

Thought for 3 sec

Completed design checks — found 170 issues.

Read BOM.

Read schematic.

Thought for 5 sec

2/4 Determine valid replacement action for U3 and R19

Thought for a moment

I inspected U3 and R19. U3 is currently TXS0102DCTR wired as the 3.3 V ↔ 5.1 V I2C level shifter, and R19 is the 4.7 kΩ SDA_5V pull-up to 5V1_LOGIC.
I’m blocked because replacing U3 requires the exact new level-shifter part/MPN, and replacing R19 requires the intended resistor value/package or whether it should be removed. Send the replacement part for U3 and the intended change for R19 — for example: “replace U3 with PCA9306” and “change R19 to 10 kΩ / remove R19.”
robocraz

robocraz

remove both and place new one

flux

0:22

Thought for a moment

I’ll remove the existing level shifter and pull-up resistor, then add a fresh level-shifter component back in place and restore its I2C/power connections without the R19 pull-up.

flux

11:31

Thought for 4 sec

3/5 Remove U3 and R19, add a fresh TXS0102DCTR level shifter, and restore connections without R19

Thought for 8 sec

Thought for 3 sec

Thought for 8 sec

4/5 Validate schematic/review for new U3 after change

Thought for 8 sec

Completed design checks — found 167 issues.

Read layout.

Read schematic.

Thought for 2 sec

5/5 Place the new U3 in the interface cluster on the PCB

Thought for a moment

Thought for a moment

Thought for a moment

Thought for 4 sec

Thought for a moment

Thought for 8 sec

Thought for a moment

Thought for 2 sec

Thought for 36 sec

Thought for 15 sec

Thought for 7 sec

6/6 Run final focused review after U3 placement

Thought for 3 sec

Completed design checks — found 242 issues.

Thought for 12 sec

6/6 tasks completed.

Thought for a moment

Done. Removed the old U3 and R19, added a fresh U3 TXS0102DCTR, restored its SDA/SCL, power, OE, and GND connections, and placed it back in the interface cluster near J1/J2 and the related resistors.
Note: R19 is now removed, so the SDA_5V pull-up is gone; SCL_5V still has R20. The focused check did not report U3/R19-related issues, but the broader project may still have the previous layout/routing issues.
Add SDA pull-up
Check level shifter
Check pull-up values
Move R20 closer

Finished working

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Dual PCA9685 Servo Controller thumbnail
Compact 4-layer dual PCA9685 servo controller with Raspberry Pi 5 and STM32 Nucleo interfaces

Properties

Properties describe core aspects of the project.

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