Author: Al Williams

4502 Articles

Retrotechtacular: Mobile Phones 1940s Style

March 13, 2020 by 24 Comments

We think of the mobile phone — well, what we would call a cell phone — as something fairly modern. Many of us can still remember when using a ham radio phone patch from your parked car would have people staring and murmuring. But it turns out in the late 1940s, Bell Telephone offered Mobile Telephone Service (MTS). It was expensive and didn’t work as well as what we have now, but it did let you make or receive calls from your automobile. After the break, you can see a promotional film about MTS.

The service rolled out in St. Louis in the middle of 1946. The 80-pound radios went in the trunk with a remote handset wired to the dashboard. At first, there were only 3 channels but later Bell added 29 more to keep up with demand. An operator connected incoming and outbound calls and if three other people were using their mobile phones, you were out of luck.

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Plastic Cleanup Via Retrobrighting

March 13, 2020 by 31 Comments

If you work on old radios, electronics is only one of the skills you need. The other is wood or metal working to restore the cabinets and chassis. However, more recent electronics have plastic and old plastic tends to turn yellow. [Odd Experiments] shows how to whiten plastic using a UV light source, aluminum foil, and hydrogen peroxide. Generally, ABS is the plastic at fault, especially those mixed with bromine as a fire retardant. You can see the results in the video below.

Note the peroxide in use was 12% — much stronger than what’s probably in your medicine cabinet. That’s usually only 3% solution, although you can get different strengths including some over 30% if you shop. However, if you search you’ll find that people have used 12%, 6%, and even 3% successfully, although we’d imagine it takes more time with 3%.

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MessagePack Is A More Efficient JSON

March 12, 2020 by 50 Comments

It is an age-old problem, that of having some data you want to store somewhere, and later bring it back. How do you format the data? Custom file formats are not that hard, but if you use an existing format you can probably steal code from a library to help you. Common choices include XML or the simpler JSON. However, neither of these are very concise. That’s where MessagePack comes in.

For example, consider this simple JSON stanza:

{"compact":true, "schema":0}

This is easy to understand and weighs in at 27 bytes. Using MessagePack, you’d signal some special binary fields by using bytes >80 hex. Here’s the same thing using the MessagePack format:

 
0x82 0xA7 c o m p a c t 0xC3 0xA6 s c h e m a 0x00

Of course, the spaces are there for readability; they would not be in the actual data stream which is now 18 bytes. The 0x82 indicates a two-byte map. The 0xA7 introduces a 7-byte string. The “true” part of the map is the 0xC3. Then there’s a six-byte string (0xA6). Finally, there’s a zero byte indicating a zero.

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An RF Engineer’s FPGA Learning Journey

March 12, 2020 by 3 Comments

[KF5N] admits he’s not a digital design engineer; he’s more into the analog RF side of things. But he’s recently taken on a project to communicate between a Ubuntu box and an Intel MAX10 FPGA. He did a presentation at a recent ham radio convention about what he’d learned and how you could get started.

The video talks a lot about the Intel (used to be Altera). However, the nearly 40 minute video after the break isn’t a step-by-step tutorial so even if you are interested in other devices, you’ll probably enjoy watching it. If you’ve programmed even one FPGA, this video likely won’t hold your interest — you aren’t the target audience. However, at about 00:31 he does recommend some books and some very inexpensive FPGA boards, so it’s not a total wash.

[KF5N] talks about what an FPGA is and how it’s different from a microcontroller. He also recommends Cornell’s [Bruce Land’s] course materials. He wasn’t a big fan of the online courses he tried. Of course, since he’s using an Intel chip, he also recommended the Intel courses. A lot of the video covers how to save on getting a development board. The Cornell class calls for a $250 board that is pretty powerful. That’s also pretty expensive, so he recommends a lighter version for about $85.

He also talks about the toolchain and his project to interface to his Linux box. He wound up with an SPI interface that ran up to 30 MHz. He also talks about using Julia to build a driver to talk to the interface on the PC side.

We didn’t notice him mentioning our own FPGA bootcamp, although he did mention projects on Hackaday.io. If you want to see a similar video but with open source tools, [David Williams] did a talk at Superconference that gives the same kind of overview but with Yosys and other related tools.

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Java On GPUs And FPGAs

March 11, 2020 by 48 Comments

There was a time when running a program on an array of processors meant that you worked in some high-powered lab somewhere. Now your computer probably has plenty of processors hiding in its GPU and if you have an FPGA, you have everything you need to make something custom. The idea behind TornadoVM is to modify OpenJDK and GraalVM to support running some Java code on parallel architectures supported by OpenCL. The system can utilize multi-core CPUs, GPUs (NVIDIA and AMD), Intel integrated GPUs, and Intel FPGAs.

If you want to try your hand at accelerated Java, there are some docker containers to get you started fast. There’ are also quite a few examples, such as a computer vision application.

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Tweet Your BBC Basic Code To The Cloud

March 7, 2020 by 1 Comment

From the “things we like, but can’t explain why file” comes the BBC-Micro-bot twitter robot. BBC Basic was a staple in the UK and if you tweet a BBC Basic program to @bbcmicrobot you’ll get a reply with a 30 second video of your program being emulated in all its glory.

As you can see in the above tweet, the code can get a bit terse, but if you look at the bot’s feed you can find some more legible examples. As the author, [@Dominic Pajak] said:

You might want to use fewer and smaller line numbers, fewer spaces and check out the minimum abbreviations for BBC BASIC keywords to achieve this.

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Farewell SETI@Home

March 6, 2020 by 59 Comments

It was about 21 years ago that Berkley started one of the first projects that would allow you to donate idle computing time to scientific research. In particular, your computer could help crunch data from radio telescopes looking for extraterrestrial life. Want to help? You may be too late. The project is going into hibernation while they focus on analyzing data already processed.

According to the home page:

We’re doing this for two reasons:

1) Scientifically, we’re at the point of diminishing returns; basically, we’ve analyzed all the data we need for now.

2) It’s a lot of work for us to manage the distributed processing of data. We need to focus on completing the back-end analysis of the results we already have, and writing this up in a scientific journal paper.

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