Monthly Archives: May 2009

While I have a couple of STM32 development boards already, I was looking around for something a bit more flexible. Somehow, development kits always seem to have the wrong set of peripherals and pins I want to play with are not available. After a bit of hunting, I came across this board, made by ETT. It comes in a convenient, small size with two single rows of pins for the IO. Perfect for plugging into a breadboards for some proper playing…

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It would be nice to start with a simple LED flashing, blinky type application. Well simple is a bit of an overstatement. The code to blink an LED is easy enough but those nice folk at ST have provided a special peripheral driver library. This library abstracts much of the hardware from the user and should make for more portable code. The library sources are all in standard C and are supposed to compile up just like anything.  Even with the benefit if an IDE, this would be a bit tricky to set up. Without one, it means a lot of messing about with makefiles, linker scripts and startup code. This is how I set up mine on a Mac. Much the same arrangement will work just fine on a PC. Included is a project template to speed things up…

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As a bit of a backup to the whole bootloader thing, I bought an Olimex ARM-USB-OCD JTAG adaptor. This is a multi purpose device that provides you with a USB JTAG interface to the ARM, a USB serial port and a power supply for your target board. It looks pretty useful and is supported by the openOCD project as well as Rowley Crossworks. JTAG is fast for flash programming and pretty well a one-touch solution in Crossworks. I was quite excited when it arrived and hurried to get it set up. By now, I should know better…

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One of the more attractive features or the STM32 processors, at least in their more recent revisions, is the presence of a built-in serial bootloader. JTAG is all very well but you need extra hardware and then software to drive it. If you want to do in-circuit debugging, it is ideal. However, for my use, I don’t much want a 20 pin header and I find the debugging feature for a micromouse to be a little redundant. Debugging can be done on a static test rig. But then, if I want to update the mouse software, a serial bootloader is perfect and I can use the same serial connection to communicate with my code when it is running

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CodeSourcery are the maintainers of the GNU Toolchain for ARM processors. They have a range of commercial offerings but, if you are prepared to use command-line tools, they also provide just those as Sourcery G++ Lite. The Lite edition includes the GNU C and C++ compilers, GNU Assembler and Linker, GNU debugger and Instruction Set Simulator. For Windows and Linux hosts, these are available as binary distributions that simply install and are ready to use. For the Mac, you need to build them from sources available on the CodeSourcery site.

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The whole ARM processor core thing is really attractive. Here is a widespread, powerful core available in a whole bunch of packages and processor combinations from a range of suppliers. Then there came the Cortex-M3 version. More interesting still is the ST processor series known as the STM32. These really are interesting. they are cheap, readily available, fast, have a peripheral set that could be made for the kind of tasks I am most interested in and you can get free or low cost development tools…

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