Arietta G25 Has Us Wondering Where ARM Boards Are Going

November 1, 2014 by Mike Szczys 40 Comments

This tidy little ARM board is the Arietta G25. It’s based around an AT91SAM9G25 which is an ARM9 chip running at 400MHz. Paired with the DDR2 RAM (in 128 or 256 meg options) to the left, the board runs Linux and runs it well. After the break you can see the obligatory running of Doom. But in this case it doesn’t just run a demo, but is playable from momentary push buttons on a breadboard (props to the Arietta team for using wire wrap for that setup).

See the vertical row of pads between the processor and the SD card slot? That’s a breakout header designed to accept a WiFi module. In at €20-30 based on your RAM choice and just €7 for the WiFi module this board is certainly a contender for any embedded Linux projects. But it does have us wondering, should be thinking of these as ARM boards, or forget the low-level development and just think of them as a Linux machines with plenty of GPIO available?

The 20×2 pin header breaks out a lot of the SAM9’s features. We really like the interactive pinout posted for this device. For instance, there are three sets of USB host lines available. But you’ll want to click on each to see that one set is in use for the SD card, and another is used by the WiFi module. The documentation that has been posted for the Arietta G25 is one of its strongest point. Nice work there!

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Dual-mode Avalanche And RF Random Number Generator

October 31, 2014 by Ethan Zonca 28 Comments

[Paul] designed a new open-hardware RNG (random number generator) that includes two sources of entropy in a small package. The first source of entropy is a typical avalanche diode circuit, which is formed by a pair of transistors. This circuit creates high-speed random pulses which are sampled by the onboard microcontroller.

What makes this design unique is a second entropy source: a CC2531 RF receiver. The RF receiver continuously skips around channels in the 2.5Ghz band and measures the RF signal level. The least-significant bit of the signal level is captured and used as a source of entropy. The firmware can be configured to use either source of entropy individually, or to combine both. The firmware also supports optionally whitening the entropy byte stream, which evens out the number of 1’s and 0’s without reducing entropy.

The OneRNG uses the USB-CDC profile, so it shows up as a virtual serial port in most modern operating systems. With the rngd daemon and a bit of configuration, the OneRNG can feed the system entropy source in Linux. [Paul] also has a good writeup about the theory behind the entropy generator which includes images of his schematic. Firmware, drivers, and hardware design files are open-source and are available for download.

Playing Doom (Poorly) On A VoCore

October 19, 2014 by Brian Benchoff 14 Comments

Last May brought the unastonishing news that companies were taking the Systems on Chip found in $20 wireless routers and making dev boards out of them. The first of these is the VoCore, an Indiegogo campaign for a 360MHz CPU with 8MB of Flash and 32MB or RAM packaged in a square inch PCB for the Internet of Things. Now that the Indiegogo rewards are heading out to workbenches the world over, it was only a matter of time before someone got Doom to run on one of them.

After fixing some design flaws in the first run of VoCores, [Pyrofer] did the usual things you would do with a tiny system running Linux – webcams for streaming video, USB sound cards to play internet radio, and the normal stuff OpenWrt does.

His curiosity satiated, [Pyrofer] turned to more esoteric builds. WIth a color LCD from Sparkfun, he got an NES emulator running. This is all through hardware SPI, mind you. Simple 2D graphics are cool enough, but the standard graphical test for all low powered computers is, of course, Doom.

The game runs, but just barely. Still, [Pyrofer] is happy with the VoCore and with a little more work with the SPI and bringing a framebuffer to his tiny system, he might have a neat portable Doom machine on his hands.

Reverse Engineering A Bathroom Scale For Automated Weight Tracking

October 18, 2014 by Rick Osgood 16 Comments

[Darell] recently purchased a fancy new bathroom scale. Unlike an average bathroom scale, this one came with a wireless digital display. The user stands on the scale and the base unit transmits the weight measurement to the display using infrared signals. The idea is that you can place the display in front of your face instead of having to look down at your feet. [Darell] realized that his experience with infrared communication would likely enable him to hack this bathroom scale to automatically track his weight to a spreadsheet stored online.

[Darell] started by hooking up a 38khz infrared receiver unit to a logic analyzer. Then he recorded the one-way communication from the scale to the display. His experience told him that the scale was likely using pulse distance coding to encode the data. The scale would start each bit with a 500ms pulse. Then it would follow-up with either another 500ms pulse, or a 1000ms pulse. Each combination represented either a 1 or a 0. The problem was, [Darell] didn’t know which was which. He also wasn’t sure in which order the bits were being transmitted. He modified a software plugin for his logic analyzer to display 1’s and 0’s on top of the waveform. He then made several configurable options so he could try the various representations of the data.

Next it was time to generate some known data. He put increasing amounts of weight on the scale and recorded the resulting data along with the actual reading on the display. Then he tried various combinations of display settings until he got what appeared to be hexadecimal numbers increasing in size. Then by comparing values, he was able to determine what each of the five bytes represented. He was even able to reconstruct the checksum function used to generate the checksum byte.

Finally, [Darell] used a Raspberry Pi to hook the scale up to the cloud. He wrote a Python script to monitor an infrared receiver for the appropriate data. The script also verifies the checksum to ensure the data is not corrupted. [Darell] added a small LED light to indicate when the reading has been saved to the Google Docs spreadsheet, so he can be sure his weight is being recorded properly.

[Sprite_TM] Puts Linux In A Clock Radio

September 18, 2014 by Brian Benchoff 11 Comments

[Sprite] needs an alarm clock to wake up in the morning, and although his phone has an infinitely programmable alarm clock, his ancient Phillips AJ-3040 has never failed him. It’s served him well for 15 years, and there’s no reason to throw it out. Upgrading it was the only way, with OLED displays and Linux systems inside this cheap box of consumer electronics.

After opening up the radio, [Sprite] found two boards. The first was the radio PCB, and the existing board could be slightly modified with a switch to input another audio source. The clock PCB was built around an old chip that used mains frequency as the time base. This was torn out of the enclosure along with the old multiplexed LCD.

A new display and brain for the clock was needed, and [Sprite] reached into his parts drawer and pulled out an old 288×48 pixel OLED display. When shining though a bit of translucent red plastic, it’s can be a reasonable facsimile of the old LEDs. The brains of the clock would be a Carambola Linux module. After writing a kernel module for the OLED, [Sprite] had a fully functional Linux computer that would fit inside a clock radio.

After having a board fabbed with the power supplies, I2C expanders, USB stereo DAC, and SPI port for the OLED, [Sprite] had a clock radio that booted Linux on an OLED screen. In the video below, [Sprite] walks through the functions of the clock, including setting one of the many alarms, streaming audio from the Internet, and changing the font of the display. There’s also a web UI for the clock that allows alarms to be set remotely – from a phone, even, if [Sprite] is so inclined.

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Bubble Displays Are Increasing In Resolution

August 14, 2014 by Rich Bremer 14 Comments

PipeDreams 3 bubble display

[Bruce] has created a pretty cool bubble display that is capable of showing recognizable photographs of people. This entire art installation is no slouch at 3-stories tall! This one resides at the Ontario Science Centre in Toronto, Canada. If you are unfamiliar with bubble displays, they consist of several clear vertical tubes filled with a liquid. A pneumatic solenoid valve mounted at the bottom of each tube allows a controlled amount of air to enter the tube at a very specific time. Since the air weighs less than the liquid, the air bubble travels up the tube of liquid. Interesting patterns can be made if these bubbles are timed correctly. This setup uses a Linux-based computer with custom control software to manipulate the valves.

[Bruce] didn’t start off making super-complex bubble displays. This is actually his 3rd go-around and with 96 individual tubes and capable of displaying raster images, it is the most complicated so far. His first creation consisted of 16 tubes, each larger in diameter than the most recent creation. With the larger diameter and less number of tubes came less resolution and the ability to only display simple shapes. Version 2 had twice as many tubes, 32 this time. In addition to doubling the tube quantity [Bruce] also colored the fluid in the tubes, not all the same color but all the colors of the rainbow, from red to violet. Still, this version could not show raster images. It appears to us that the third time’s the charm! Video after the break….

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Raspberry Pi Backup Scripts

August 11, 2014 by Rick Osgood 19 Comments

Raspberry Pi

[Matthew’s] recent blog post does a good job explaining the basics of the Raspberry Pi’s file system. The Linux operating system installed on a Pi is generally installed on two different partitions on an SD card. The first partition is a small FAT partition. All of the files on this partition are used for the initial booting of the Pi. This partition also includes the kernel images. The second partition is the root file system and is generally formatted as ext4. This partition contains the rest of the operating system, user files, installed programs, etc.

With that in mind you can deduce that in order to backup your Pi, all you really need to do is backup all of these files. [Matt] has written some scripts to make this a piece of cake (or pie). The first script will simply copy all of the files into a gzipped archive. You can save this to an external SD card, USB drive, or network share.

The second script is perhaps more interesting. This script requires that you have one free USB port and a USB SD card reader. The script will automatically format the extra SD card to contain the two critical partitions. It will then copy the “boot” files to the new boot partition and the root file system files to the new SD card’s root partition. When all is said and done, you will end up with an SD card that is an exact copy of your current running file system.

This can be very handy if you have multiple Pi’s that you want to run the same software, such as in a Pi cluster. Another good example is if you have spent a lot of time tweaking your Pi installation and you want to make a copy for a friend. Of course there are many ways to skin this cat, but it’s always fun to see something custom-built by a creative hacker.