I wrote my first firmware for the DEFCON badge. Doesn't do much other than replace the default Knight Rider LED sequence with my own, but it's a first step. I did want to note a couple of things that were not mentioned in the badge hacking information that might make it easier to get started.
There are two drivers for windows, one when the badge is in USB bootloader mode and one while the badge is in normal mode. To get to bootloader mode you need to hold down the mode select button while inserting the battery. The driver provided on the CD is for normal mode which took me a while to figure out. To get to the normal mode you need to plug the USB cord in BEFORE you insert the battery. Looking at the firmware I noticed the check for a USB connection is done as one of the very first things. Windows will then recognize the device and you can install the driver from the CD. The driver for bootloader mode is actually part of the Freescale JM60 bootloader program which can also be found on the CD but must be installed before you try bootloader mode.
Also, I couldn't get the full version of Code Warrior so the next best thing was the demo from Freescale. But, the demo has a 32k firmware limit which means removing some of the original firmware code. I removed fat.c from the project and recompiled and fixed until I got it working. This will of course remove your ability to read or write to the SD card using FAT.
Next step is to make the final hack which will hopefully be done by tomorrow so we can show it off to Kingpin. I'll post the final hack information and code tomorrow if it gets done.