Posted on February 20, 2015 at 11:10The first thing I will say is that 100 ms is a ''long time'' in microcontroller terms.
So we might ask what might your stm32 be doing that takes 100 ms?
Looking closely, I see that your green trace seems to have a small sine wave during the 100 ms that your yellow trace is high. A credible explanation is that both pins are floating, and that your external hardware happens to pull the yellow trace high and the green trace low during this 100 ms.
So my next thing question is when might you assign both pins to be floating inputs?
My answer:
At power-up/reset, I expect all pins to be floating inputs except where specified by the data sheet (e.g. those which can be used by JTAG have specific pull-up/down to comply with JTAG specs without the need for external resistors).
And I would also expect GPIO_Deinit to put the pins back into this state.
So what is taking 100 ms?
That might be the time from your debug system resetting your processor to it coming out of reset and calling GPIO_Configuration();
Hope this helps,
Danish
