My first thought when I got one of those boards was to build a quadcopter, but then I decided that was too conventional, so I elected to build a tricopter. The three motor setup makes yaw control a challenge, as it is coupled with the other degrees of freedom, but that was to be part of the fun. Not gotten very far along, I'm sad to say.
I have a "copter" of some description, except the whole thing spins. There's the central little body, two wings (at 12:00 and 6:00 say), and two arms with small props (3:00 & 9:00), which thrust horizontally, not vertically. Hovering is...a challenge.
These MCUs are fantastic in terms of performance, cost and functionality. We've got many great ideas we are making reality; however the real key to all of this is software. The choices you have are:
single loop of control with mcu vendor software
commercial or free kernel with mcu vendor software
commercial rtos (which is a kernel + I/O )
Time to market for a single product launch is key. Total cost of ownership is key for lines and families of products.
To win commercially, a commercial RTOS is easily the best choice for either a single product or line of products. Mant close to the hardware don't realize this. The reasons for this are:
mcu vendors are good at hardware, the software is a free throw in that nobody cares about as long as you purchase chips
integration/test is 50% of the development cost - this should be free with a good rtos
an RTOS provides much better performance than a single loop over a wide range of features
Also aherence to industry standards can further reduce your costs if you are going the RTOS route. Full POSIX solutions are now available for mcu rtoses and this means better software reuse and knowledge reuse.
As an example, see what you can get from www.rowebots.com and compare the development/integration costs to the actual total life cycle costs other approaches deliver. There are 90+ demonstrations running out of the box with all wireless options, all networking options, all usb options, many file systems and more for the Unison RTOS on STM32.
Using the compass as a current probe is an interesting idea. Is it sensitive enough? How's its linearity? Did you find an APP note somewhere that told you how to do that, or are you going to figure it out some other way?
I was semi-kidding, but it could work...maybe. It's a 3d compass/magnetometer – will have to read the datasheet to see what I can learn. E.g., I don't even have a clue how the ambient magnetic field compares to current in a wire... Also, given the chip is on the board, it wouldn't be a very useful probe :-}
Six or seven months ago, I evaluated several inexpensive MCU boards as ways to teach kids about computers and let them have their own computer, too. Unfortunately, the STM32 board fell short in a number of ways, so I urge caution before you use it for experiments or a project.
Setup was easy (I used the Atollic software tools), so I decided to use an I/O port for some tests--flash LEDs, display counts on LEDs, and so on. It took a long time to understand how the ports work and all the registers involved--configuration, data, set/reset, locking, and others. It took several restarts and a re-installations of the Atollic tools to get anything but the pre-programmed demo program to run. The Atollic docs need some rewriting and editing, too. Take a look at the 8-bit LED program in the Atollic examples. No kid would want to type in all this information, let alone try to understand it. 96 Lines of C code to control an output port! Wow. One statement should do it.
Also, the dual rows of headers on each long side of the board make connection to a breadboard quite difficult. Even with all of the interesting devices, I never warmed to the STM board as an educational tool. Perhaps engineers and programmers would have less difficulty, but schedule a lot of time to plow through the manuals to find information you need.
By the way, I evaluated several other MCU demo boards from large semiconductor companies and found all wanting in one way or another. I finally chose a board from a small company and might have time to describe it in a Dev-Monkey blog on the EDN site.