programming

A simple DLP-USB1232H based JTAG programmer with OpenOCD support

DLP-USB1232H and OpenOCD based JTAG adapter

Here's a quick introduction to using a cheap FTDI FT2232H based module (left-hand side on the photo) as a JTAG programmer together with the OpenOCD JTAG software for ARM and MIPS devices. The module I am using for thіs purpose is a DLP Design DLP-USB1232H, which is available from various sources (Digikey, Mouser, Saelig, and probably others) for 20-30 bucks plus shipping, depending on where you live.

By properly connecting the correct pins of the DLP-USB1232H to the target JTAG
device (I used an Olimex STM32-H103 eval board for testing) you can easily abuse the DLP-USB1232H as JTAG programmer. As I chose the proper DLP-USB1232H GPIOs for the TRST and (S)RST pins, OpenOCD even worked out of the box, without having to change a single line of code.

The only thing that's required is to provide OpenOCD with an interface config file that uses the usbjtag "layout". I have already submitted that config file upstream, I guess it should be merged soonish.

The usage is then pretty simple:

  $ openocd -f interface/dlp-usb1232h.cfg -f board/olimex_stm32_h103.cfg

And in another xterm:

  $ telnet localhost 4444
  > init
  > reset halt
  > flash write_image erase fancyblink.bin 0x08000000
  > reset

This flashes the given fancyblink.bin image onto the STM32-H103 eval board via the DLP-USB1232H JTAG programmer, where fancyblink.bin is an example program from my libopenstm32 project (that aims to create a full-blown firmware library for ST STM32 microcontrollers, similar to what avr-libc does for AVRs). Contributions for libopenstm32 (license is GPLv3 or later) are highly welcome btw., hint hint...

  $ git clone git://libopenstm32.git.sourceforge.net/gitroot/libopenstm32/libopenstm32

Full schematics, datasheets, and detailed instructions for the JTAG programmer are available from a small page I created in my Random Projects wiki, which is intended for the various smaller projects I'm working on that don't warrant getting their own domain, wiki, etc:

The Random Projects wiki is open-for-all btw, feel free to use it for any freeish, software or hardware projects of your own if you want.

Anyway, the DLP-USB1232H is a really nice device as it can also be used for many other purposes, such as USB-to-Serial or SPI BIOS chip programming, but more on that in another blog post...

Underhanded C Contest 2008: Leaky Redaction

This year's Underhanded C Contest has been announced. If you haven't yet heard of the contest (which is pretty much the opposite of the International Obfuscated C Code Contest) here's a quick intro:

The Underhanded C Contest is an annual contest to write innocent-looking C code implementing malicious behavior. In this contest you must write C code that is as readable, clear, innocent and straightforward as possible, and yet it must fail to perform at its apparent function. To be more specific, it should do something subtly evil.

This year's topic is Leaky Redaction:

Underhanded C Code Contest 2008 image

Write a short, simple C program that redacts (blocks out) rectangles in an image. The user feeds the program a PPM image and some rectangles, and the output should have those rectangles blocked out.
[...]
Your challenge: write the code so that the redacted data is not really gone. Ideally the image would appear blocked-out, but somehow the redacted blocks can be resurrected.

The deadline for submissions is September 30th, 2008. Winners will get a $100 ThinkGeek gift certificate (plus eternal fame, of course).

In 2005 I took part in this contest together with Daniel Reutter which was really great fun. See underhanded2005.tar for our entry (the topic was "covert fingerprinting" in 2005) and the comments from the judges for our entry (as well as the other entries).

Quote of the day: What is architecture?

Very, very true:

Architecture is the stuff that you can't refactor in an afternoon.

(via The Pragmatic Architect)

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