Linux Fu: Gum Up Your Script

March 29, 2023 by Al Williams 11 Comments

We often write quick bash scripts and judging by the comments, half of us use bash or a similar shell to pop out quick, useful scripts, and half of us think that’s an abomination, and you should only use bash for your command line and resort to something more like a traditional language to do anything else. If you’re in the former camp, you’re probably cursing your allegiance when you need to make your bash scripts more interactive.

Gum can help. It’s a utility that can handle your script input and output with a little flair while requiring almost no effort on your part.

The command looks simple, but it has twelve subcommands, each with myriad options. But you can break down the functions into a few simple categories. The input commands let you prompt for a line of input or a bunch of lines of input. You can also create a pick list or a yes/no type of prompt. There’s also a file picker and a filter, sort of like fzf.

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EPROM Does VGA

March 29, 2023 by Al Williams 16 Comments

If you wanted to create a VGA card, you might think about using an FPGA. But there are simpler ways to generate patterns, including an old-fashioned EPROM, as [DrMattRegan] points out in a recent video.

Generating video signals is an exercise in periodicity. After all, an old-fashioned CRT just scans at a certain horizontal frequency and refreshes the entire screen each time it starts over. VGA is made to drive this technology. An EPROM chip can easily generate repeating patterns when driven by a counter at a known frequency.

As you might expect, there were a few software glitches to work out, but in the end, the circuit did its job, displaying a fixed image on a VGA monitor.

If you haven’t run into [Matt] before, he has a complete series on how he built a “wire-by-wire” Apple II clone. We will warn you, though. Don’t click on the link unless you have some spare time. The 18 videos take over two hours to work through, but there is some beautiful prototyping and a lot of good information in them.

You can go even lower tech for a VGA card, if you like. Just try not to look like this breadboard.

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A Comprehensive Look At FDM Supports

March 27, 2023 by Al Williams 14 Comments

When we first started 3D printing, we used ABS and early slicers. Using supports was undesirable because the support structures were not good, and ABS sticks to itself like crazy. Thankfully today’s slicers are much better, and often we can use supports that easily detach. [Teaching Tech] shows how modern slicers create supports and how to make it even better than using the default settings.

The video covers many popular slicers and their derivatives. If you’ve done a lot with supports, you might not find too much of this information surprising, but if you haven’t printed with supports lately or tried things like tree supports, you might find a few things that will up your 3D printing game.

One thing we really like is that the video does show different slicers, so regardless of what slicer you like to use, you’ll probably find exactly what different settings are called. Of course, because slicers let you examine what they produce layer-by-layer, you can do like the video and examine the results without printing. [Michael] does do some prints with various parameters, though, and you can see how hard or easy the support removal is depending on some settings. The other option is to add support to your designs, as needed manually, or — even better — don’t design things that need support.

This video reminded us of a recent technique we covered that added a custom support tack to help the slicer’s automatic support work better. If you want a longer read on supports that also covers dissolvable support, we’ve seen that, too.

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The 4004 Upgrade You’ve Been Waiting For

March 26, 2023 by Al Williams 5 Comments

You know how it is. You have an older computer, and you can’t run the latest software on it. Time to upgrade, right? Well, if you have been in this situation a very long time, [ryomuk] may have an answer for you. The emu8080on4004 project (Google Translate) offers a way to run 8080 code on a 4004 CPU. Finally!

The 4004 development board is a homebrew affair, and the emulator works well enough that an 8080 Tiny BASIC interpreter ran with very few changes to the source code. You can see it working in the video below. It would be cool to run CP/M, but we imagine that would be a little harder, especially resource-wise.

A few things are missing. For example, the DAA instruction doesn’t exist, and there are no provisions for interrupts. There’s only one I/O port, and using the IN instruction will block until you receive a serial port character. There is an option to implement the parity flag in the 8080 flags register, but its operation is untested.

Still, pretty impressive for a 4-bit CPU running at 740 kHz with very little memory. If you want to see more about the development board itself, check out the second video below. Want to know more about the chip that launched a family of processors that is still around? Read its biography. You can also read about the designer who put his signature on the die.

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IBIS Models Explained

March 26, 2023 by Al Williams 2 Comments

If you’ve worked with circuit simulation, you may have run into IBIS models. The acronym is input/output buffer information, and while you can do a lot without having to deal with IBIS, knowing about it can help you have a successful simulation.

IBIS is an industry-standard format that uses ASCII text to describe voltage versus current and voltage versus time about some device’s digital input and output pins. This allows precise simulation without revealing the device’s internals, which is important to some vendors. The first post of this two-part series talks about what IBIS is and how it got started. The second part explains creating and using LTSpice to create your own IBIS models. It also covers why you might want to do that.

Of course, if you don’t care about revealing the internals of a device, you could just create a Spice simulation. However, many tools will accept both models, so it is useful to know how to produce either kind of model. In fact, to create an IBIS model, you’ll want to use a Spice model to generate the data for the IBIS model, so it is a good bet you’ll have both, even if you choose to only publish the IBIS models.

If you need a refresher on Spice, we have a series. If you prefer using something different, try Micro-Cap 12, which was commercial, but went free a few years ago.

Recreating One Of History’s Best Known Spy Gadgets

March 25, 2023 by Al Williams 22 Comments

[Machining and Microwaves] got an interesting request. The BBC asked him to duplicate the Great Seal Bug — the device the Russians used to listen covertly to the US ambassador for seven years in 1945. Turns out they’re filming a documentary on the legendary surveillance device and wanted to demonstrate how it worked.

The strange thing about the bug is that it wasn’t directly powered. It was actually a resonant cavity that only worked when it was irradiated with an external RF energy. Most of the video is background about the bug, with quite a few details revealed. We particularly liked the story of using a software defined radio (SDR) to actually make the bug work.

As you might expect, things didn’t go smoothly. Did they ever get results on camera? Watch the video, and you can find out. This is just the first of six videos he plans to make on the topic, and we can’t wait for future videos that cover the machining and more technical details.

We’ve examined the Theremin bug before. There’s a definite cat-and-mouse dynamic between creating bugging devices and detecting them.

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Inside Digital Image Chips

March 25, 2023 by Al Williams 8 Comments

Have you ever thought how amazing it is that every bit of DRAM in your computer requires a teeny tiny capacitor? A 16 GB DRAM has 128 billion little capacitors, one for each bit. However, that’s not the only densely-packed IC you probably use daily. The other one is the image sensor in your camera, which is probably in your phone. The ICs have a tremendous number of tiny silicon photosensors, and [Asianometry] explains how they work in the video you can see below.

The story starts way back in the 1800s when Hertz noticed that light could knock electrons out of their normal orbits. He couldn’t explain exactly what was happening, especially since the light intensity didn’t correlate to the energy of the electrons, only the number of them. It took Einstein to figure out what was going on, and early devices that used the principle were photomultiplier tubes, which are extremely sensitive. However, they were bulky, and an array of even dozens of them would be gigantic.

Semiconductor devices use silicon. Bell Labs was working on bubble memory, which was a way of creating memory that was never very popular. However, as a byproduct, the researchers realized that moving charges around for memory could also move around charges from photosensitive diodes. The key idea was that it was harder to connect many photodiodes than it was to create the photodiodes. Using the charge-coupled device or CCD method, the chip could manipulate the charges to reduce the number of connections to the chip.

CCDs opened up the digital image market, but it has some problems. The next stage was CMOS chips. They’d been around for a while since IBM produced the scanistor, but the sensitivity of these CMOS image chips was poor. Since most people were happy with CCD, there wasn’t as much research on CMOS. However, CMOS sensors would eventually become more capable, and the video explains how it works.

We’ve looked at image sensors before, too. The way you read them can make a big difference in your images.

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