Electric Imp Makes A Cat Door Tweet Its Activities

January 4, 2013 by Mike Szczys 11 Comments

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This Tweeting cat door uses the Electric Imp to read a sensor and report back to the server. The hardware is pretty neat. The board hosts an ARM Cortex-M3 processor and gets on your home network via WiFi. The mini-USB cable simply provides the power. Programming is done over the network. Our own [Brian Benchoff] had a chance to try the Imp out earlier in the Fall.

Monitoring a cat door is as good a reason as any to undertake a project. The hardware added to the board includes a reed switch mounted on the jamb along with a magnet on the door itself. There is also a blue LED that gives a bit of user feedback. The software isn’t quite as easy but it still wasn’t that bad. As with most web-connected projects getting all the parts to talk to each other was a bit of a chore. The Imp reports back to a server on the local network which then activates a PHP script that uses Sen.se to push out a Tweet.

[Thanks Pat]

Stellarino Brings Wiring-style Coding To The Stellaris Launchpad

December 19, 2012 by Mike Szczys 18 Comments

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[Sultan Qasim] wrote in to tell us about the work he’s been doing on the Stellarino library. It’s goal is to break down the coding barriers present for those looking to move from Arduino to ARM. This is accomplished by facilitating Wiring-stlye code for the Stellaris Launchpad ARM development board.

Right off the bat [Sultan] mentions that the interface is Wiring-like, but is not compatible with it. This means you can’t just plop your existing sketches into a C file and get them to work with the addition of a simple include file. But what it does do is provide access to the functions to which seasoned Arduino users have grown accustomed. You can see some examples above, including analogWrite(), digitalRead(), and a simple delay function.

We had a quick look at the library. It uses StellarisWare components which are stored in the ROM of the chip (these are all preceded by ‘ROM_’). The one thing missing is the UARTstudio library which apparently carries a license incompatible with GPL.

Using Newlib With Stellaris Launchpad

December 18, 2012 by Mike Szczys 20 Comments

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[Brandon] is taking us further down the rabbit hole by demonstrating how to use newlib with the TI Stellaris Launchpad. This is a nice continuation of the framework he built with his post about using GCC with ARM hardware. But it is most certainly one level of complexity deeper than that initial article.

Using newlib instead of glibc offers the option of compiling C code that includes system calls common when coding for computers but which are rare in embedded systems. Using something like printf is generally avoided because of the overhead associated with it. But these processors are getting so fast and have so much RAM that it may be useful in certain cases. We briefly thought about implementing malloc for creating a linked list when working on our STM32 snake game. [Brandon’s] work here makes the use of that command possible.

The process starts by adding labels for the beginning and end of the stack/heap. This makes it possible for functions to allocate memory. After taking care of the linker script changes you must implement a few system call functions like _sbrk.

ARM Powered Rack Mount USB Test Equipment

December 13, 2012 by Mike Szczys 8 Comments

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This is a device which [Limpkin] has been developing at his day job. It’s a high-speed testing interface for use with Physics experiments. We find it interesting because it uses an ARM microcontroller to implement CDC and MSD over USB.

The design is in two parts to make it work in a rack-mount situation. That big white connector allows cards to be swapped out. You can see the board on the right has a USB-A connector. When plugged in this enumerates as a control device (CDC) and a mass storage device (MSD) using fat32 as a file system.

The platform is being developed with open hardware and open source software in mind. If you’re working on a project that uses either of these USB functionalities this makes a swell reference. The ARM Cortex-M3 chip that he’s using is an AT91SAM3U but it should not be too hard to port the code for other similarly-capable ARM processors.

Level Converters To Make All Your Hardware (5.5V And Under) Play With Each Other

December 11, 2012 by Mike Szczys 18 Comments

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I finally set aside some time for one of my own projects. I have been playing around with ARM microcontrollers a lot lately and wanted to try out my GLCD display that uses the KS0108 protocol. It’s 5V but I had heard that some of these displays will work with 3.3V TTL. But the datasheet tells me otherwise. I tried using a pull-up resistor to 5V and configuring the Stellaris Launchpad pins to open drain, but the low voltage wasn’t getting below the 0.3V threshold needed by my display. My only choice was to use some type of level conversion. I actually ended up driving the KS0108 using a pair of TXB0108 level converters.

I figured this had to have been done before so I check over at Sparkfun. Their offerings are either one-way or have a direction pin that you must drive yourself. I figured there had to be a bi-directional solution and a search over at Mouser led me to the TXB0108. It is exactly what I was looking for and as you can see I etched my own circuit boards to make the TSSOP chips breadboard compatible. I’ve documented the process you can find the code and board files at my post linked above.

Update: one of the Reddit comments mentions this chip is available on a breakout board from Adafruit if you’re interested.

Building An ARM Cross Compiler On OSX

December 7, 2012 by Mike Szczys 11 Comments

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We’ve tried building our own ARM cross compiler on a Linux box and it’s no picnic. Luckily there is a free cross compiling toolchain available through Mentor Graphics (formerly called Code Sourcery G++). But those looking to develop on a Mac aren’t so lucky. There is help via a script, and [Michael] wrote a guide detailing how to use crosstool-ng to build an ARM toolchain on Mountain Lion.

Crosstool-ng is a script which automates much of what is needed when compiling all the different components. But there is a some groundwork that needs to be in place before you can run it. For instance, some of the tools that ship with OSX aren’t entirely compatible with the GNU tools the script is looking for. One example is ‘grep’. Mountain Lion has the BSD version of grep but it is missing a few of the GNU version’s commands used by crosstool-ng. [Michael] will guide you through this and a handful of other issues until you have a functioning toolchain up and running.

Mass Storage Bootloader For Stellaris Launchpad

December 7, 2012 by Mike Szczys 5 Comments

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[Andrzej Surowiec] liked the functionality of the mass storage bootloader available on some NXP LPC development boards. His latest project was to write a mass storage bootloader for the Stellaris Launchpad. It allows you to flash your compiled firmware to the chip simply by mounting the board as a USB storage device and copying over the binary file. The chip has plenty of flash memory (the bootloader itself takes up 16 KB of the available 256 KB), and the board is already set up for use as USB hardware.

There is a precompiled binary available at the linked page above or you can get the source code from his github repository. We think this project is a good stepping off point for others. For instance, it should be relatively easy to use [Andzej’s] work as the base for implementing filesystem-based I/O control like we saw in the phatIO project.