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The distributors finally got in some of the new ST Micro STM32F2 series uControllers and I grabbed a few.  I was able to "shoehorn" one into a ver5 board as the pinout is close to compatible with the performance STM32F1 series.  Spent a few days rewriting the device drivers and am very impressed with this controller's performance.

I was able to bump up the sample rate to around 276.8KHz for all 12 sensors for a total of ~3.32 million samples per second.  Despite this more than doubling of work load, I ended up with around 70% idle time, up from 60% of the STM32F1.  Keep in mind that at a 120MHz clock rate, this 70% free cycles represents more than twice as much free number crunching capability than the STM32F1 at 60% idle.  I also found that the DMA to be much better with full FIFO available on each DMA channel and an easier to use triple ADC.

The result is a much cleaner interpretation of the sensor data which translates to a smoother and more stable platform.

Take a look at this short demo of the STM32F215 in a hex frame:


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  • incredible! great job!
  • Good job Bill.
  • Wow!!!!!

  • awesome!!!
  • awesome!!!
  • Thanks, Bill.

     I was excited when I learned of the Kinetis, only to be disappointed when I found out it currently lacked the FPU (although I think their latest series will have one). I did acquire a Piccolo Control Stick from TI. It has an FPU and a "control law accelelerator", which can run floating point control loops (but can only be programmed in assembler). I might try to use it in a quad.


    - Roy


  • Sort of like this blog announcement from November 2010...
  • the m4 will be available from nxp in october.

    it is a dual core mcu :)

  • Roy: I can find no reason to use the old STM32F1 instead of the F2. They have improved too many things. I was going to wait for the M4, but until when? And if it is missing the optional FPU (like Freescale's Kinetis) then there would be little advantage in waiting. I am not using I2C but I don't remember seeing anything about it in the errata. Of course it is still too early to know all of the problems with the F2, but I have proven that it does at least as much as I need.
  • Congrats, Bill! Great work, as always.


    So, do you think its worth it to go from SMT32 F1 to F2, or would it make more sense to wait for Cortex M4? Also, do you know if the F2 series corrects the bug with hardware I2C (I'm not sure if you're even using I2C)?


    - Roy

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