Getting SPI On A Router

August 17, 2013 by Brian Benchoff 13 Comments

router

Cheap routers such a s the TP-LINK 703n and the TP-LINK MR3020 (seen above) can be used for much more than just connecting your laptop to your cable modem. They’re actually very small Linux boxes and with OpenWRT, you can control every aspect of these tiny pocket-sized computers. It’s frequently been suggested that these routers are awesome substitutes for the usual methods of getting Internet on a microcontroller, but how do you actually do that? The onboard serial port is a great start, but this also dumps output from the Linux console. What you need here is an SPI connection, and [ramcoderdude] has just the solution for you.

Linux already has a few SPI modules, but these are only accessible with kernel drivers. Traditionally, the only way to access SPI is to recompile the kernel, but [coderdude] created a kernel module that allows any device running the Attitude Adjustment OpenWRT image to dynamically allocate SPI busses.

He’s already submitted this patch to the OpenWRT devs, and hopefully it will be included in future updates. Very cool, we think, and something that can open a whole lot of doors for hacking up routers very easily.

Electronic Wedding Attire For A Geeky Wedding

August 16, 2013 by Mathieu Stephan 15 Comments

In the past we featured many projects that were used at [Bill] and [Mara]’s wedding. However we forgot the most important thing: their electronically enhanced clothes.

As you can see from the picture above, the wife opted for LEDs while the husband preferred Electro Luminescent (EL) wires/panels. The ATtiny based platform LilyTiny was picked to control all the LEDs, and charlieplexing was implemented as only 4 IO pins were available. Animations were made using Vixen and exported via a python script.

To power the EL wires, [Bill] hacked a Sparkfun EL battery pack/inverter. He removed the shell and took out the inverter part, reverse engineered the design enough to figure out how to bypass the onboard microcontroller that generated the on/off/blink function. Finally, he 3D printed enclosures to pack the electronics with one Li-Ion battery pack. A boost regulator was used to supply the 12v required by the EL panel power supply.

Don’t forget to also check out their centerpieces and wedding invitations that we previously featured.

Making The Electronics For A Doppler Motion Sensor

August 14, 2013 by Mathieu Stephan 30 Comments

There are many different sensors that can be used to detect motion in a given environment. Passive InfraRed (PIR) sensors are the most used today, as they work by detecting moving heat signatures. However, they are less reliable in the hotter days and obviously only work for animals and humans.

Sensors like the one shown in the above picture started to appear on the internet, they use the doppler effect to detect motion. I (limpkin) designed the electronics you need to add in order to get them to work.

Here is a simple explanation of the doppler effect: if you send an RF signal at a given frequency to a moving target, the reflected signal’s frequency will be shifted. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession. Continue reading “Making The Electronics For A Doppler Motion Sensor” →

Playing With An Oscilloscope You’ll (probably) Never Own

August 14, 2013 by Mathieu Stephan 30 Comments

We’ll have to admit that we were really jealous when [Shahriar] sent us a video he made, in which he casually explains how a $500,000 160GS/s 62GHz oscilloscope works and then starts playing with it.

Even though you need to be quite familiar with electronics to fully understand the oscilloscope’s inner workings, [Shahriar]’s step by step explanation is still approachable for those who only understand the basics.

In the first half of the video he uses the manufacturer’s documentation which contains the oscilloscope block diagrams, so you’ll also learn about:

timer interleaved Analog to Digital Converters (ADCs), which allows you to increase your input sampling rate by using several of them
phase-locked loops, which use a reference clock to generate a much faster clock signal
custom made dies and the materials used for high frequency electronic components

In the second half of the video [Shahriar] connects a pseudo random binary sequence generator and uses the oscilloscope to make several measurements that you’d typically want to know for high speed signals (jitters, eye quality factor…). He later performs a small experiment where he up-converts the frequency components of two random 3.12Gbit/s signals and tries to recall each original signal using the oscilloscope functions, making this part of the video a bit harder to keep up with.

Designing A Pressure Sensitive Floor

August 13, 2013 by Mathieu Stephan 37 Comments

[Sean] and his team at Adobe were asked to build “something new” for the Children’s Creativity Museum in San Francisco, so in several months they managed to build a digital/physical environment for kids called “Sense It”.

Part of this project involved designing and building a pressure-sensitive electronic floor which could detect if children were sitting, walking or running. As a camera based detection system couldn’t give them the type of precision they wanted, [Sean] decided to use pressure-sensitive resistors placed under MDF panels.

There are a total of twenty-one 2’x4′ tiles, each one including 8 pressure-sensitive resistors and an ATtiny84 based platform. All the microcontrollers digitize their 8 sensor signals and send their conversion results to a beaglebone over a shared i2c bus in a RJ45 CAT5 cable. As it is [Sean]’s first project, we will cut him some slack but several design mistakes have been made in our opinion:

Using i2c instead of RS485 / CAN for long distance data transmission
Digitizing the sensor voltages so far from them, as noise is added before the ADC
Sending the +5V required by the ATtiny in the RJ45 cable instead of a higher voltage (which would involve putting an LDO on the platforms)
Separating the digital and analog ground planes as the platform current consumption is low and transmission speeds slow

But the children who can now play with the complete system certainly won’t care. And you… what do you think of [Sean]’s work? Don’t hesitate to let us know in the comment section below.

Hacking Transcend Wifi SD Cards

August 12, 2013 by Mathieu Stephan 107 Comments

[Pablo] is a recent and proud owner of a Transcend WiFi SD Card. It allows him to transfer his pictures to any WiFi-enabled device in a matter of seconds.

As he suspected that some kind of Linux was running on it, he began to see if he could get a root access on it… and succeeded.

His clear and detailed write-up begins with explaining how a simple trick allowed him to browse through the card’s file system, which (as he guessed correctly) is running busybox. From there he was able to see if any of the poorly written Perl scripts had security holes… and got more than he bargained for.

He first thought he had found a way to make the embedded Linux launch user provided scripts and execute commands by making a special HTTP POST request… which failed due to a small technicality. His second attempt was a success: [Pablo] found that the user set password is directly entered in a Linux shell command. Therefore, the password “admin; echo haxx > /tmp/hi.txt #” could create a hi.txt text file.

From there things got easy. He just had to make the card download another busybox to use all the commands that were originally disabled in the card’s Linux. In the end he got the card to connect a bash to his computer so he could launch every command he wanted.

As it was not enough, [Pablo] even discovered an easy way to find the current password of the card. Talk about security…

A Crystal Radio Amplifier In A Jar

August 11, 2013 by Mathieu Stephan 20 Comments

The cool thing with crystal radios is that they are solely powered by the incoming radio waves. However, it usually means listening to your AM radio station with an earpiece and even then, depending on the antenna length, ground connection, and radio station, it can be quite hard to hear.

Even though it is cheating, [Steven] decided to make an amplifier for all the different crystal radios he had made over the years. His design, based on an LM386 amplifier was firstly tested on a breadboard and then permanently soldered onto a perfboard. To make the complete system easy to transport, he opted for a peanut butter jar where he embedded the speaker in the cap. The on/off switch and volume controls are mounted on the side, and easy alligator clips are used for the antenna connection.

The final result is not the one shown in the picture above as [Steven] painted the jar black, giving it a sweet look.