Differential pairs!

Published

October 10, 2024

Written by

Sergiy Nesterenko

Founder and CEO

Read the Full Series

This article is one part of a walkthrough detailing how we recreated an NXP i.MX 8M Mini–based computer using Quilter’s physics-driven layout automation.

Overview: Project Speedrun

Part 1: Preparing the Design

Part 2: Compiling the Design

Part 3: Cleaning Up the Design

Part 4: Testing & Validation

We recently added support to Quilter for differential pairs and I could not wait to try the feature out on the QSP32 Solar Boost!

When I uploaded my schematic, Quilter automagically detected the pairs between USB and UART.

Schematic clip showing where a set of differential pairs are located.

Quilter's UI automatically detects differential pairs

Quilter did a great job of placing the FTDI chip close to the USB-C connector.

I put probes on DP_P and DP_N (white arrows). These traces go between a UART chip (top) and a USB-C connector (bottom). The layout of the differential pairs have precise length matching for good signal integrity.

White arrows pointing to where probes are on DP and DN

Take a look at these perfectly mirrored signals! This feature works perfectly, I had three boards fabbed and each one connects instantly to upload sketches.

Next up: energy harvesting from a tiny solar panel

Try Quilter for Yourself

Project Speedrun demonstrated what autonomous layout looks like in practice and the time compression Quilter enables. Now, see it on your own hardware.

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Validating the Design

With cleanup complete, the final question is whether the hardware works. Power-on is where most electrical mistakes reveal themselves, and it’s the moment engineers are both nervous and excited about.

Continue to Part 4

Cleaning Up the Design

Autonomous layout produces a complete, DRC'd design; cleanup is a brief precision pass to finalize it for fabrication.

Continue to Part 3

Compiling the Design

Once the design is prepared, the next step is handing it off to Quilter. In traditional workflows, this is where an engineer meets with a layout specialist to clarify intent. Quilter replaces that meeting with circuit comprehension: you upload the project, review how constraints are interpreted, and submit the job.

Continue to Part 2