Posted on February 13, 2014 at 09:11shorting Idd makes board to stop working completly, and my computer running win7 reporting a usb power surge when im doing this.
Not sure if you speak about the present or the past.
But when shorting the 3V3 supply to ground, the MCU will certainly stop working, because it is not supplied any more.
all this hapened after tryed to measure with the internal A/D
an AC 4Vp-p signal on a DC offset at 18Volts
thought that adding caps to the pins and then applying the signal wont make any problems but sadly it did. the board turned off instantly, since then doesnt work.
That sounds a little bit different.
18V are way above the 3.6V or 5V the datasheet specifies, so expect the MCU at least partially fried (protective diodes at GPIOs zapped).
but even if mcu is dead it doesnt even worth replacing it with a new one because it costs almost the same as the whole discovery board
I can't look at the board across this forum, but my first guess is it is dead - at least the target part. You may consult a hardware expert near you, to have a look at. But I would try to remove the ldo or the protective shottky diode (assuming the supply part is similiar to other STM32 discovery board I have), and check if the ''USB surge'' persists. Perhaps just some external and easily replaced circuitry (like the ldo) is fried up.
However, I would pal up with the idea to scrap the board, and file the issue under 'lessons learned'. BTW, I have killed much more expensive boards in my career ...
