The Voyager Computer

I like both spacecrafts and old computers. Here is a quote about the Voyager computers from the 1970’s. It is worth to think about what you can do with very little. I suppose the peripherals where more analog and less computerized in this setup. Still, they made it work.

Question: What kind of computers are used on the Voyager spacecraft?

Answer: There are three different computer types on the Voyager spacecraft and there are two of each kind. Total number of words among the six computers is about 32K.

Computer Command System (CCS) – 18-bit word, interrupt type processors (2) with 4096 words each of plated wire, non-volatile memory.

Flight Data System (FDS) – 16-bit word machine (2) with modular memories and 8198 words each

Attitude and Articulation Control System (AACS) – 18-bit word machines (2) with 4096 words each.

According to my calulations, that’s a total of about 68KB, or small potatoes compared to today’s microprocessors. We probably could perform all functions with one of today’s boards and still have room for solid state data storage and much more fault detection software. We would still need a second unit for redundancy. Today’s microprocessors are also much faster than the chips used on Voyager and a comparative system would use less electrical power. On the other hand, software might be more complicated as opposed to that used in an interrupt type system, but it would be much more capable and more flexible.

Let’s look closer at the CCS. The CCS has two main functions: to carry out instructions from the ground to operate the spacecraft, and to be alert for a problem or malfunction and respond to it. Two identical 4096- word memories contain both fixed routines (about 2800 words) and a variable section (about 1290 words) for changing science sequences. The CCS issues commands to the AACS for movement of the scan platform or spacecraft maneuvers; to the FDS for changes in instrument configurations or telemetry rates and to numerous other subsystems within the spacecraft for specific actions. Fault-protection algorithms are also stored in the CCS, occupying roughly 10 percent of the CCS memory.

The main functions of the FDS are to collect data from, and controls the operations of, the scientific instruments; and to format engineering and science data for on-board storage and/or real-time transmission. The FDS also keeps the spacecraft “time” and provides frequency references to the instruments and other spacecraft subsystems.

The Voyager spacecraft computers are interrupt driven computer, similar to processors used in general purpose computers with a few special instructions for increased efficiency. The programming is a form of assembly language.

There is no clock chip, as such, in the spacecraft. The “clock” is really a counter, based on one of several electronically generated frequencies. These frequencies, based on a reference, generated by a very stable oscillator, are converted and fed to different locations in the spacecraft as synchronization signals, timers, counters, etc. The “clock” signal is part of the information telemetered to the ground and it is with ground software that we convert to day of year, time of day Greenwich Mean Time.

Voyager was built in-house at JPL; the computers were manufactured by General Electric to JPL specifications.

Question: How fast are the Voyager computers?

Answer: Not very fast compared to today’s standards. The master clock runs at 4 MHz but the CPU’s clock runs at only 250 KHz. A typical instruction takes 80 microseconds, that is about 8,000 instructions per second. To put this in perspective, a 2013 top-of-the-line smartphone runs at 1.5 GHz with four or more processors yielding over 14 billion instructions per second.

Via Stephan Korsback, original source unknown.

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A desktop CNC

othermillAs 3D printing becomes popularized, the opposite, milling (i.e. removing instead of adding material) is trying to reach the same tipping point. Over at kickstarter, the Othermill has achieved funding.

Milling opens the possibilities of working with a wider set of materials. It also makes it possible to create custom PCBs in a snap. No more chemicals and manual drilling. As the technology is similar to that of 3D printing, a large part of the needed work is already out there – electronics, g-code interpreters, etc.

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Rhombus-Tech is a CIC company working on various hardwares for running open source software. They are involved in a number of interesting projects, one of them being the KDE tablet. Their site makes an interesting read and they carry lots of information.

For instance, they make a computer module based on the Allwinner A10.

The Allwinner A10 CPU has been developed in, and is sold in, the People’s Republic of China. Its mass-volume price is around $7, yet it is a 400-pin highly feature-rich 1.2ghz ARM Cortex A8 with a MALI400 GPU. It has the distinction of having the highest bang-per-buck ratio of any SoC available at the time of writing, by quite a margin.

Based on this, they are also looking at a laptop project, a game console project and how to use the A10 in education.

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The people behind lowpowerlab has come up with a nice solution to switching your Raspeberry Pi on and off. Using a microcontroller and letting it communicate with the Pi over GPIO, the power supply is kept in sync with the Pi. All is explained in the video below.

Via hackaday.

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Machine Code for Beginners

The great Introduction to Machine Code for Beginners by Lisa Watts and Mike Wharton from 1983 is available online.

This book is a simple, step-by-step guide to learning to program in machine code. Machine code is the code in which the computer does all its work and programs written in machine code runs much faster and take up less memory space than programs in BASIC. A machine code program, though, is much more difficult to write and less easy to understand than a program in BASIC.

I remember reading this as a kid, so I presume that it was translated into Swedish. Still, a colourful introduction to how the machine thinks. I’ll show it to my daughter this weekend.

Via BoingBoing.

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Arduino from the Command Line

Feeling limited by the Arduino IDE? What to avoid writing linked scripts by hand? Try Ino.

Ino may replace Arduino IDE UI if you prefer to work with command line and an editor of your choice or if you want to integrate Arduino build process to 3-rd party IDE.

Ino is based on make to perform builds. However Makefiles are generated automatically and you’ll never see them if you don’t want to.

Sounds like the best of two worlds to me!

via SparkFun.

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Raspberry Pi Camera Available

The Raspberry Pi Foundation just announced the availability of the long awaited camera board.

The camera boards are now available for order! You can buy one fromRS Components or from Premier Farnell/Element14. We’ve been very grateful for your patience as we’ve tweaked and refined things; it’d have been good to get the camera board out to you last month, but we wanted your experience to be as good as possible, and we’ve been working on the software right up until last night.

For such a small device, this has been an enormous project, and a year-long effort for everybody involved. We’re pretty proud of it: we hope you like it!

For the curious minded, there is a small video demonstrating how to get it started.

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ESD Safety

Or, you can read up on Wikipedia.

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LEGO runs Linux

GyroBoyOldest CES news of the year, but I’m just very happy to hear that the next generation of Lego MindStorm will run Linux!

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Capacative Touch

Adafruit is a great resource for may electronic projects. One of my favorite parts is their focus on wearable electronics. Gizmos with LEDs and speakers have been around for a while. You can even get them from Thinkgeek. However, capacitive touch with conductive fabric opens possibilities.

I’m not sure if this ever will become mainstream. But imagine having sensors for vitals integrated in your t-shirt. Monitoring pulse, breathing, etc without any clumsy sensors. This, coupled with movement-based power generation, I’m sure we will see more and more in the future.

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