Posted on July 01, 2016 at 13:20From what I understand, STM32F407VET6 identifies a processor, not a board.
Your board might connect port B pin 8 to some other circuitry and that might be where the current is flowing (rather than the processor) which causes the LED to glow. As
we
don't know what test board you are using, we can't rule that out as a possibility.
Other thoughts:
You say you program the pin to be an input (and the LED still glows). If you program the pin to be an ANALOG input, or an input with either PULL_UP or PULL-DOWN, I would expect it to draw current when you pull it externally above Vdd.
Another possibility is if your code is not keeping the pin as input-floating. If you have it output for even 1 microsecond every few milliseconds then that will be enough to make the LED look as though it is glowing continuously. If you stick in an endless loop after programming the pin to be input-floating then you can be more confident that the remainder of your code is not defeating your current test.
What voltage do you measure on the pin? (And how does that compare to the processor's Vdd).
Do you have access to an oscilloscope so you can see if the voltage is stable rather than pulsing?
Hope this helps,
Danish
