Apollo-era PCB Reverse Engineering To KiCad

November 25, 2024 by Chris Lott 24 Comments

Earlier this year [Skyhawkson] got ahold of an Apollo-era printed circuit board which he believes was used in a NASA test stand. He took high quality photos of both sides of the board and superimposed them atop each other. After digging into a few obsolete parts from the 1960s, he was able to trace out the connections. I ran across the project just after making schematics for the Supercon badge and petal matrix. Being on a roll, I decided to take [Skyhawkson]’s work as a starting point and create KiCad schematics. Hopefully we can figure out what this circuit board does along the way.

The board is pretty simple:

approximately 6.5 x 4.5 inches
22 circuit edge connector 0.156 in pitch
31 ea two-terminal parts ( resistors, diodes )
3 ea trimmer potentiometers
7 ea transistors
parts arranged in 4 columns

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Supercon 2024 SAO Petal KiCad Redrawing Project

November 19, 2024 by Chris Lott 4 Comments

Last week I completed the SAO flower badge redrawing task, making a complete KiCad project. Most of the SAO petals are already released as KiCad projects, except for the Petal Matrix. The design features 56 LEDs arranged in eight spiral arms radiating from the center. What it does not feature are straight lines, right angles, nor parts placed on a regular grid.

Importing into KiCad

Circuit Notes for LEDs, Thanks to [spereinabox]

I followed the same procedures as the main flower badge with no major hiccups. This design didn’t have any released schematics, but backing out the circuits was straightforward. It also helped that user [sphereinabox] over on the Hackaday Discord server had rung out the LED matrix connections and gave me his notes.

Grep Those Positons

I first wanted to only read the data from the LEDs for analysis, and I didn’t need the full Kicad + Python scripting for that. Using grep on the PCB file, you get a text file that can be easily parsed to get the numbers. I confirmed that the LED placements were truly as irregular as they looked.

My biggest worry was how obtain and re-apply the positions and angles of the LEDs, given the irregular layout of the spiral arms. Just like the random angles of six SAO connector on the badge board, [Voja] doesn’t disappoint on this board, either. I fired up Python and used Matplotlib to get a visual perspective of the randomness of the placements, as one does. Due to the overall shape of the arms, there is a general trend to the numbers. But no obvious equation is discernable.

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Supercon 2024 Flower SAO Badge Redrawing In KiCad

October 31, 2024 by Chris Lott 12 Comments

Out of curiosity, I redrew the Supercon Vectorscope badge schematics in KiCad last year. As you might suspect, going from PCB to schematic is opposite to the normal design flow of KiCad and most other PCB design tools. As a result, the schematics and PCB of the Vectorscope project were not really linked. I decided to try it again this year, but with the added goal of making a complete KiCad project. As usual, [Voja] provided a well drawn schematic diagram in PDF and CorelDRAW formats, and a PCB design using Altium’s Circuit Maker format (CSPcbDoc file). And for reference, this year I’m using KiCad v8 versus v7 last year.

Importing into KiCad

This went smoothly. KiCad imports Altium files, as I discovered last year. Converting the graphic lines to traces was easier than before, since the graphical lines are deleted in the conversion process. There was a file organizational quirk, however. I made a new, empty project and imported the Circuit Maker PCB file. It wasn’t obvious at first, but the importing action didn’t make use the new project I had just made. Instead, it created a completely new project in the directory holding the imported Circuit Maker file. This caused a lot of head scratching when I was editing the symbol and footprint library table files, and couldn’t figure out why my edits weren’t being seen by KiCad. I’m not sure what the logic of this is, was an easy fix once you know what’s going on. I simply copied everything from the imported project and pasted it in my new, empty project. Continue reading “Supercon 2024 Flower SAO Badge Redrawing In KiCad” →

Experimenting With MicroPython On The Bus Pirate 5

October 15, 2024 by Chris Lott 4 Comments

I recently got one of the new RP2040-based Bus Pirate 5 (BP5), a multi-purpose interface debugging and testing tool. Scanning the various such tools in my toolbox already: an Analog Discovery 2, a new Glasgow Interface Explorer, and a couple of pyboards, I realized they all had a Python or MicroPython user interface. A few people on the BP5 forums had tossed around the idea of MicroPython, and it just so happened that I was experimenting with building beta versions of MicroPython for a RP2350 board at the time. Naturally, I started wondering, “just how hard can it be to get MicroPython running on the BP5?”

The Lazy Approach

Rather than duplicating the BP5 firmware functionality, I decided to ignore it completely and go with existing MicroPython capabilities. I planned to just make a simple set of board definition files — perhaps Board Support Package (BSP) is a better term? I’ve done this a dozen times before for development and custom boards. Then write a collection of MicroPython modules to conform to the unique aspects in the BP5 hardware. As user [torwag] over on the Bus Pirate forums said back in March:

Micropython comes already with some modules and enough functions to get some stuff out-of-the-box working. E.g. the infamous version of “hello world” for microcontrollers aka led-blinking.

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RP2040 Boot Loader Is A Worm

March 17, 2024 by Chris Lott 8 Comments

[Hunter Adams] has written a secondary bootloader for the RP2040 that uses an IR link and can be extended to behave like a polite worm virus. This allows the easy updating of a large cluster of co-located RP2040-based controllers. This could be handy in applications like swarm robotics or virtual cattle fencing. The project he demonstrates in the two videos ( below the break ) uses a pair of IR transmitters/receivers. But he purposely wrote the boot loader to be independent of the serial link, which could be infrared, radio, audio, or just wires.

Not only did [Hunter] make a boot loader, but he documented the entire boot process of the RP2040 chip. Whether or not you need a secondary bootloader, this is an excellent resource for understanding how the RP2040 responds to power cycling and resets. The boot loader code is available at his GitHub repository.

You may recall that [Hunter] is the lecturer of Cornell University’s Designing with Microcontroller classes, whom we’ve mentioned before. We’ve also covered some of his students’ projects as well, like these air drums and this CoreXY pen plotter.

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Arctic Adventures With A Data General Nova II — The Equipment

February 5, 2024 by Chris Lott 51 Comments

As I walked into the huge high bay that was to be my part-time office for the next couple of years, I was greeted by all manner of abandoned equipment haphazardly scattered around the room. As I later learned, this place was a graveyard for old research projects, cast aside to be later gutted for parts or forgotten entirely. This was my first day on the job as a co-op student at the Georgia Tech Engineering Experiment Station (EES, since renamed to GTRI). The engineer who gave me the orientation tour that day pointed to a dusty electronic rack in one corner of the room. Steve said my job would be to bring that old minicomputer back to life. Once running, I would operate it as directed by the radar researchers and scientists in our group. Thus began a journey that resulted in an Arctic adventure two years later.

The Equipment

The computer in question was a Data General (DG) mini computer. DG was founded by former Digital Equipment Corporation (DEC) employees in the 1960s. They introduced the 16-bit Nova computer in 1969 to compete with DEC’s PDP-8. I was gawking at a fully-equipped Nova 2 system which had been introduced in 1975. This machine and its accessories occupied two full racks, with an adjacent printer and a table with a terminal and pen plotter. There was little to no documentation. Just to turn it on, I had to pester engineers until I found one who could teach me the necessary front-panel switch incantation to boot it up. Continue reading “Arctic Adventures With A Data General Nova II — The Equipment” →

Simon Says With An RP2040

January 30, 2024 by Chris Lott No comments

The team of [Michael] and [Chimdi] from Cornell’s Designing with Microcontrollers (ECE 4760) Fall 2023 session designed a version of Simon Says on an RP2040 which they call Pico Says. It uses UDP packets over WiFi to communicate between the players, and supports VGA graphics for output. Each player’s hardware consists of a Pico W module plus a control panel containing the four LEDs and buttons ( red, green, yellow, and blue ) plus send and reset buttons.

For purposes of this lab, the modules were build on a solderless breadboard and used perfboard for the control panels. They weren’t entirely happy with their choice of UDP because they experienced frequent datagram dropouts in the noisy environment of the microcontroller lab. They also planned to implement sound effects, but ran out of time after spending too much time on the WiFi implementation, and had to drop that feature. In the end, however, they wrapped up their project and demonstrated a working game. We can only speculate whether this bonus lesson in resource management was intended by [Dr. Hunter Adams] or not.

Two ECE 4760 course references are highlighted in the write-up that helped them jump-start the project: the UDP and VGA examples for the Pico. These are good links to put in your RP2020 toolbox for future projects, in addition to the ECE 4760 course home page itself. We’ve covered several of these projects recently, as well as the curriculum switch from the Microchip PIC32MX-based Microstick II to the RP2040 last Spring.

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