[Arm-netbook] stm32f072 usb firmware

[Luke Kenneth Casson Leighton]

On Fri, Oct 16, 2015 at 4:41 PM, Peter Bouda <peter at ubrew.it> wrote:
>
>> keep the little piece of card, you need it!  it has the pin-out
>> assignments.  so forget powering by the micro-usb, do this:
>>
>>   * flip the jumper from E5V to U5V
>>   * cut off a random USB cable and strip down the black, red, white and
>> green
>>   * solder 5V (Red) to pin 6 of CN7
>>   * solder GND (black) to pin 8 of CN7
>>   * solder USB+ (green) to pin 12 (PA12) of CN10
>>   * solder USB- (white) to pin 14 (PA11) of CN10
>>
>> then, plug it into a USB port of the development machine.  then, use a
>> screwdriver to short BOOT0 (pin 7 of CN7) to E5V (pin 6 of CN7), and
>> at the same time press and then release the reset button (B2).
>>
>>   if you then do "lsusb" you should see a device come up "DFU mode" in
>> the description.  ta-daa, you can now upload a .bin file to it.  you
>> do that with any of the libopencm3-examples, you must do "make bin".
>
>
> hm, that did not work, unfortunately, I cannot get into the DFU mode
> somehow. It will just start into the mode that is described in the Quick
> start section of the manual. I found some forum posts where people suggest
> to solder resistors to PA11 and PA12... but that should not alter the start
> mode, right?

 that's for very older STM32F devices, where they did not have the
resistors built-in.  occasionally you might need 22R resistors to stop
signals bouncing back-and-forth with incorrect impedance, but you
shouldn't.


> Any ideas what I could have done wrong?

 it's not amazingly hard, this, there's not actually a lot to do, so
the number of things wrong will be very small.

  can you take a picture and make it available online, also compare
against the photo here:
 http://rhombus-tech.net/community_ideas/laptop_15in/news/PCB2_prototype_progress_14oct2015/

 btw if you haven't re-flashed the firmware at all, then by default it
will come up with LD2 blinking happily.  check first that that's what
happens by returning the U5V jumper and plugging in a mini-usb cable.

 btw you should *NOT* plug in a mini-usb cable at the same time as the
USB cable across PA12 and PA11!

 also make sure BOOT0 is shorted to E5V *before* pressing reset, then
hold reset for at least 0.5 seconds, *then* release reset, then
release BOOT0 screwdriver-short.

 l.