Retrotechtacular: Where The Linux/UNIX TTY Came From

February 11, 2014 by Mike Szczys 27 Comments

retrotechtacular-tty-demystified

From time to time we realize that sayings which make sense to us probably will have no meaning for future generations. Two of the examples that spring to mind are “hang up the phone” or in a vehicle you might “roll down the window”. And so is the case for today’s Retrotechtacular. Linux users surely know about TTY, but if you look up the term you actually get references to “Teletypewriter”. What’s that all about?

[Linus Akesson] wrote a fantastic essay on the subject called The TTY Demystified. We often feature old video as the subject of this column, but we think you’ll agree that [Linus’] article is worth its weight in film (if that can be possible). The TTY system in Linux is a throwback to when computers first because interactive in real-time. They were connected to the typewriter-mutant of the day known as a teletype machine and basically shot off your keystrokes over a wire to the computer the terminal was controlling.

This copper pipeline to the processor is still basically how the terminal emulators function today. They just don’t require any more hardware than a monitor and keyboard. We consider ourselves fairly advanced Linux users, but the noob and expert alike will find nuggets and tidbits which are sure to switch on the lightbulb in your mind.

[Thanks Chuck]

Retrotechtacular is a weekly column featuring hacks, technology, and kitsch from ages of yore. Help keep it fresh by sending in your ideas for future installments.

Making The Worst Linux PC Useful

November 21, 2013 by Brian Benchoff 16 Comments

AVR

After seeing [Dimitry] build the most minimal Linux computer ever, [Kyle] decided he needed one for himself. In true hacker fashion, he decided to take this build for the worst Linux PC one step further: he would add I2C to his version, making it somewhat useful, considering the number of I2C peripherals out there.

This build is based on [Dmitry]’s ARM Linux computer emulated on an 8-bit AVR. It’s a full-blown Linux computer with 16 MB of RAM courtesy of a 30-pin SIMM, a lot of storage provided by an SD card, all running on an emulated ARM processor inside a lowly ATMega1284p. [Kyle] built this clone over the course of a few months, but from the outset decided he wanted to implement an I2C protocol on this terribly under specced computer.

After booting his computer, [Kyle] eventually got an I2C module loaded by the kernel. With an I2C module and a few spare GPIO pins, he set out to create something to attach to this terribly slow computer – an ancient LED dot matrix display. With a real-time clock, this display became a clock with the help of a homebrew program written in C. Considering the speed of the emulated processor, the program takes nearly three seconds to read the RTC and display the current time to the display. We’re thinking it was a wise choice to only implement hours and minutes in this clock.

If having a useful computer running at about 10 kilohertz isn’t enough, [Kyle] also compiled the classic text-based adventure Zork. It actually runs, proving you don’t need Megahertz of power to do something useful and fun.

Linux On A Leapster For Classic Video Game Emulation

November 8, 2013 by Brian Benchoff 20 Comments

Christmas is coming, and if you have nieces, nephews, or ankle biters of your own roaming your house, you’re probably wondering how you’ll be subsidizing Santa this year. it looks like Toys R Us will be selling the Leapfrog LeapsterGS for $30 on Black Friday this year. It’s a Linux device running on a 550 MHz ARM 9, with 128 MB of RAM and 2 GB of Flash. Overpowered for a children’s toy, but perfect for when the kids forget about it in a month, because now you can replace the firmware with a proper Linux install and run classic emulators.

Putting Linux on these cheap handhelds made for children isn’t anything new; we’ve seen it done with the Leapfrog DIDJ and the Leapfrog Explorer. Those consoles, however, had rather anemic CPUs and not a whole lot of RAM. Moore’s Law finally kicked in for stocking stuffers, it seems, and the Leapster GS is powerful enough to play all those Nintendo, Game Boy and even MAME games.

All that’s needed to flash the new firmware is soldering a few wires onto the LeapsterGS’ board for a serial connection. The new LeapsterGS firmware even has an MP3 and movie player, so even if the recipient of one of these machines grows tired of it in a week, there’s still a lot of life left in it.

Video of the LeapsterGS playing the greatest arcade game below.

Continue reading “Linux On A Leapster For Classic Video Game Emulation” →

Can An 8 Node Raspberry Pi Cluster Web Server Survive Hackaday?

November 5, 2013 by Adam Fabio 50 Comments

Plenty of folks have used their Raspberry Pi as a web server. [Steve] however is the first 8 node load balanced pi cluster server we’ve run into. While we have seen pi clusters before, they’ve never been pressed into service as a public facing web server. [Steve] has created a really nice informative website about the Raspberry Pi, and Linux in general. As his page views have increased, he’s had to add nodes to the server. Currently [Steve] sees about 45,000 page views per month.

At first glance it would seem that the load balance system would be the weak link in the chain. However, [Steve] did realize that he needed more than an Pi to handle this task. He built the load balancer using an old PC with 512MB of RAM and a 2.7GHz x86 CPU. The most important thing about the balancer is dual network interfaces, one side facing the internet, the other facing the Pi cluster. The balancer isn’t a router though. Only HTTP requests are forwarded. The Pi nodes themselves live on their own sub net. Steve has run some basic testing with siege, however nothing beats a real world test. We figured a couple of links in from Hackaday would be enough to acid test the system.

VT100 Gets BeagleBoned

October 16, 2013 by Adam Fabio 19 Comments

vt100

How do you make a great terminal even better? The answer is simple: add a BeagleBone Black to it! [Brendan] got his hands on one of the staples of classic computing, the DEC VT100 terminal. The VT100 was produced from 1978 to 1983. The terminal was so widely used that it became the standard for other terminals to emulate. Open any terminal program today and chances are you’ll find a setting for VT100 emulation.

[Brendan] originally hooked his terminal up to a laptop running Linux. The terminal, cables, and the laptop itself became quite a bit to manage on a small desk. To combat this he decided to add a BeagleBone Black inside the terminal case. It turns out the VT100 actually lends itself to this with its Standard Terminal Port (STP) connector. The STP was designed to add a “paddle board” in-line with the serial stream of the terminal. DEC and third party manufacturers used this port to add everything from disk drives to entire CPM computers to the VT100.

[Brendan] began by designing a board to interface between the VT100 and the BeagleBone. The board level shifts serial lines from the BeagleBone to the VT100. The STP also allows the terminal to provide power to the BeagleBone Black. He did notice some power glitches as the supply of the VT100 came up. This was solved with a standard TI TL77xx voltage supervisor chip. The hardest part of the entire design was the card edge connector for the STP. [Brendan] nailed the dimensions on the first try. In the end [Brendan] was rewarded with a very clean installation that didn’t require any modification to a classic piece of hardware.

We should note that most PCB houses use Electroless Nickel Immersion Gold (ENIG) as their standard coating. This will work for a card edge connector that will be plugged in and removed a few times. Cards that will be inserted and removed often (such as classic console cartridges) will quickly scrape the ENIG coating off. Electroplated Gold over Nickel is the classically accepted material for card edge connectors, however the process most likely is not going to come cheap in hobbyist quantities.

A Motherboard For A WiFi Enabled SD Card

October 9, 2013 by Brian Benchoff 14 Comments

Over the last few months, a few very capable hackers have had a hand in cracking open a Transcend WiFi-enable SD card that just happens to be running a small Linux system inside. The possibilities for a wireless Linux device you can lose in your pocket are immense, but so far no one has gotten any IO enabled on this neat piece of hardware. [CNLohr] just did us all a favor with his motherboard for these Transcend WiFi SD cards, allowing the small Linux systems to communicate with I2C devices.

This build is based upon [Dmitry]’s custom kernel for the Transcend WiFiSD card. [CNLohr] did some poking around with this system and found he could use an AVR to speak to the card in its custom 4-bit protocol.

The ‘motherboard’ consists of some sort of ATMega, an AVR programming header, a power supply, and a breakout for the I2C bus. [Lohr] wired up a LED array to the I2C bus and used it to display some configuration settings for the WiFi card before connecting to the card over WiFi and issuing commands directly to the Linux system on the card. The end result was, obviously, a bunch of blinking LEDs.

While this is by far the most complex and overwrought way to blink a LED we’ve ever seen, this is a great proof of concept that makes the Transcend cards extremely interesting for a variety of hardware projects. If you want your own Transcend motherboard, [CNLohr] put all the files up for anyone who wants to etch their own board.

Advanced Transcend WiFi SD Hacking: Custom Kernels, X, And Firefox

September 19, 2013 by Adam Fabio 95 Comments

[Dmitry] read about hacking the Transcend WiFi cards, and decided to give it a try himself. We already covered [Pablo’s] work with the Transcend card. [Dmitry] took a different enough approach to warrant a second look.

Rather than work from the web interface and user scripts down, [Dmitry] decided to start from Transcend’s GPL package and work his way up. Unfortunately, he found that the package was woefully incomplete – putting the card firmly into the “violates GPL” category. Undaunted, [Dmitry] fired off some emails to the support staff and soldiered on.

It turns out the card uses u-boot to expand the kernel and basic file system into a ramdisk. Unfortunately the size is limited to 3MB. The limit is hard-coded into u-boot, the sources of which transcend didn’t include in the GPL package.

[Dmitry] was able to create his own binary image within the 3MB limit and load it on the card. He discovered a few very interesting (and scary) things. The flash file system must be formatted FAT32, or the controller will become very upset. The 16 (or 32)GB of flash is also mounted read/write to TWO operating systems. Linux on the SD card, and whatever host system the card happens to be plugged in to. This is dangerous to say the least. Any write to the flash could cause a collision leading to lost data – or even a completely corrupt file system. Continue reading “Advanced Transcend WiFi SD Hacking: Custom Kernels, X, And Firefox” →