Upcoming Technical Content

Posted on by Alex O'Donnell

I know that this blog has drifted away from technical issues and towards the life of an engineer. I hope to fix that soon, and I am researching a few subjects.

An RS485 transceiver connected to the device under test, a host PC, and two oscilloscope probes.
  • RS485
    • Monitoring with Saleae.
    • Monitoring with HHD Serial Monitor.
    • Auto-direction RS485 transceivers.
    • Auto-direction transceivers and STM32 UART bootloader on a shared bus.
  • Documentation
    • Book review – Diagrams as Code by Omar Kamal.
    • Mermaid – a second look.
    • CircuiTikZ, Circuit Macros, and LaTeX.

RS485

I’ve just spent 6 months working on an RS485-based system for use in the transportation sector. I had a few pain points, primarily since the vehicle chassis provides the ground, and the serial port only presented A and B. A quickly built test harness gave me a really noisy signal. My Rigol scope nicely decoded the signal using the math function, and the RS485 transceiver connected to my PC had no problem, but my Saleae was caught out by all the noise. I was also monitoring low voltage signals on my Saleae at the time, and the voltage swing on the RS485 meant that too much of the signal decoded as a logic high. I don’t think I learned anything about UART over RS485 this time around, but I learned a lot about the limits of my tooling.

Documentation

I finally got a few cycles to think about my book. Some illustrations that are missing in the book are logic circuits and functional equivalent block diagrams for IC components. In my rough draft, I have grabbed resources from assorted data sheets. Oftentimes, they show what I want to show, but I have not sought permission to use them yet, and some diagrams add complexity that is not needed.

IMU Functional block diagram
Logic gate diagram. result = (!A&B)|(A&!B)

I know I can draw these diagrams with packages like Visio or draw.io, but adding connect points to rectangles to form IC package pinouts gets fussy and repetitive. I started to look for tools to help and found wrappers around LaTeX, such as CircuiTikZ. There is a world of learning there.

I stumbled across a book that might help me take my PlantUML or Mermaid to the next level. The full title is

Diagrams as Code
Exploring Mermaid, PlantUML, D2
Generating Diagrams using AI LLMs

I have hopes for this volume and will let you know my thoughts later. I’m a couple of chapters in and already know I can actually use some of these tools locally instead of using the web portals and online tools.

Static Content as well as the blog

I have recently started an online notebook for myself. It’s linked at the top of the blog. Right now, it’s rough notes and random ideas loosely organized by subject. The notes are maintained in a private GitHub repo and presented as a GitBook.

I am also cleaning up the static pages on this website. I originally intended the articles to contain valuable information, with contents being refined over time. For now I’ll just say “watch this space.“

This is Our Space

I write what I enjoy writing about; for the book, that is debugging serial protocols, for the Blog, I enjoy sharing what I learned recently. I am trying to gauge what is valuable for everyone reading along. If you have any suggestions or requests for future content, then please leave a comment. Thanks.

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