As part of the ongoing PMR-171 reverse engineering project, I ported Doom to the radio’s STM32H743 as an exercise in bare-metal development on this hardware. The STM32H743 is a Cortex-M7 at 400 MHz with 2 MB of flash, 1 MB of SRAM, and a hardware FPU — the original Doom ran on a 33 MHz 486 with 4 MB of RAM. This post documents the port.

The PMR-171 (and all its Guohetec siblings) display a small 100x100 pixel logo on a simple background when they boot. I wanted to replace it with a full-screen image. The result is an open-source Python tool that takes any image and produces a ready-to-flash firmware file. No debug probe required.

The PMR-171 is a portable all-band SDR transceiver that I recently got my hands on. Naturally I’m curious to know how this HF/VHF/UHF portable SDR works. This post covers the major ICs, signal chains, and how everything connects at a high level.

The Weigl ProCommander4 show controller crossed my path recently, and curiosity got the better of me.

Weigl Control makes show control equipment for professional and prosumer applications. This is a look at the ProCommander4’s hardware — what’s on the board, how the pieces fit together, and what that tells us about how it works. Impatient readers can skip straight to the block diagram.

Gilderfluke devices use a 3.5mm TRS jack for RS-232 communication. The combination of a bulky D-Sub connector and a thin pigtail cable is not ideal for carrying around — a minor annoyance, but one I decided to solve. This simple passive adapter converts a DB9 to a 3.5mm jack, so I can use any off-the-shelf audio cable for the run to the device instead.

I picked up a Guohetec PMR-171 portable SDR recently. It’s a compact manpack-style transceiver—roughly double the size of a Yaesu FT-817, or comparable to a typical 100W rig—covering HF through UHF with FM, AM, SSB, and even DMR support. The problem? The manufacturer’s programming software has limited capabilities and is completely undocumented. Coming from other radios with proper CPS (Customer Programming Software), I wanted to understand how this one worked.

A somewhat common issue with these radios is losing all audio. If a unit’s built-in speaker doesn’t make a pop sound or power-on tone when powered on — and the codeplug checks out fine — the audio amplifier has likely failed.

The VXR-1000 is a mobile repeater meant to be used with a mobile radio in a vehicle. Since these 5W output analog radios are designed for interfacing with other equipment via a single dsub connector and are fairly compact, they’re good candidates to use as an embedded radio in various industrial applications. In this post I document what I needed to do to get one up and running.

For Disneyland’s 70th anniversary, they released this giant lightup key which contains a pin which you can unlock by inserting the key into various locks around the park. I decided to retrofit the key with an ESP01 running WLED.

Here’s a quick post documenting the LCARS graphics I made for my Anytone AT-D878UVII handheld.

About a year ago, I began volunteering at the Los Angeles Live Steamers Railroad Museum, and quickly felt the need to build myself a train to zip around the club’s ~1.5 miles of track located in the picturesque northeast corner of Griffith Park. Rather than build a prototypical locomotive, I decided to make what’s commonly referred to as a “pedal car” with some unique features.

In late 2023, I was once again contracted by Artistic Entertainment Services (AES) to reconfigure the animatronic control system I designed and built with them for the 2023 parade for reuse on the San Diego Zoo Wild Animal Park’s 2024 Tournament of Roses entry. Like last year, this float features a cast of zoo residents animated to interact with riders on the float. I am thrilled that this float won the sweepstakes award for the most beautiful entry!

A few years ago, I built some hardware to allow an oscilloscope to be used as a VGA display. I often use the photo above as my profile/avatar online and get asked why there are crosshairs on me… here’s how it works!

For configuring Gilderfluke based animation control systems for the Rose Parade, I need a handful of computer accessories which are only available as individual components and would be both expensive to purchase and annoying to carry in the field. I built my own Gilder-Ground Support Equipment, or G2SE, box which combines several of these devices in a convenient rugged enclosure.

The basic LEDs that come in the Mickey sorcerer hat that Disney sells are rather pathetic. We can rebuild him. We have the technology.

In late 2022, I was contracted by Artistic Entertainment Services (AES) to design and program an animatronic control system for the San Diego Zoo Wild Animal Park’s 2023 Tournament of Roses entry. This rapid turnaround project leveraged compact electrical and hydraulic driven mechanisms to animate a pair of giraffes which park guests are interacting with from the back of a safari truck.

This summer I started riding a motorcycle, and while stuck at home, I designed and built an auxiliary LED indicator system for added visibility. The system uses addressable LEDs, allowing the compact controller with an integrated power supply to manage potentially hundreds of LEDs.

For my senior project, I’m working on an embeddable lighting controller, with the creative working title of Embedded Lighting Controller, which is being designed to provide flexible lighting control/drive in an extremely compact package.

For a number of projects I’d like to work on in the future, I needed a development board of sorts for testing both hardware and software.

On the morning of January 1, 2019, the La Cañada Flintridge Rose Parade float’s new animation system successfully made its debut, animating the float Tree Frog Night.

For TwinkleWorks’s new line of RGBW LED strobes, we needed a new testing assembly. This unit automatically tests each of the LEDs’ colors as well as the strobe fixture’s temperature sensing circuitry.

Testing, calibrating, and programming of the La Cañada Flintridge float’s animation system requires some support hardware. The system uses several communications busses, as well as several hardware enable and status lines which all need to be accessed for programming.

The new La Cañada Flintridge Rose Parade float’s animation system has a controller unlike anything used in the parade. The custom controller has a 12 inch waterproof touchscreen that sports a custom control GUI and convenient system configuration capabilities.

The new La Cañada Flintridge rose parade float’s animation system is built in several modular pieces. Four identical units will be valve bank modules, which are responsible for controlling a bank of four hydraulic animation channels.

The La Cañada Flintridge Rose Parade float is equipped with a custom-built intercom and radio system to allow the float’s crew to communicate both within the float, and with external crew. Since the intercom box is mounted in the middle of the float where it’s not easily accessible, we needed some way to be able to remotely control the radio.

Following my previous project involving accessing my car’s CAN bus, I wanted to take CAN control further by making a custom controller that can interface with a vehicle to control various accessories.

As of 2018, the La Cañada Flintridge rose parade float’s animation system is nearly 20 years old. As the system continues to age, components that are no longer manufactured are slowly beginning to fail. Starting in 2017, I began work on a replacement.

Have you ever had a piece of equipment that really REALLY doesn’t belong in your car, but you want to install it somehow? Well, I had this problem with my Whelen… electric airhorn….