Reordered EXTI reset code in HAL_GPIO_DeInit()

[jelledevleeschouwer]

Scenario: Firmware configures a GPIO for EXTI line interrupt on falling edge. In hardware the GPIO is pulled to Vdd by a pull-up resistor. After the falling edge is detected (single instance), the firmware reconfigures the GPIO pin for a different purpose.

Problem: EXTI line interrupt is triggered twice, while in fact only one falling edge is generated on the I/O pin.

Root cause: Improper EXTI reset order in HAL_GPIO_DeInit(). After the first time the EXTI line interrupt is fired, the firmware calls HAL_GPIO_DeInit() to de-initialize the GPIO pin because the resource is not needed anymore. Because the way the code is ordered in HAL_GPIO_DeInit(), '1'-to-'0' transition might be arise in the "Input data register" because the mode is reset to Analog High Impedance mode. This disable the internal Schmitt trigger, which continuously produces a '0' on its output. If the I/O was pulled high by pull-up resistor, a '1'-to-'0' transition triggers the EXTI line edge detector and fires the IRQ because the EXTI line configuration registers are not yet reset at this point in HAL_GPIO_DeInit().

Solution: Reorder the EXTI reset code in HAL_GPIO_DeInit() to disable the EXIT line interrupt before switching the value of EXTI line multiplexer and resetting the mode of the GPIO pin to analog high-impedance mode.

Fixes #1.

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[jelledevleeschouwer]

Hi @ALABSTM,

I cannot access https://cla.st.com/ at this moment to sign the CLA. The connection is reset by the server.

Best regards, Jelle

[CCASTM]

Hello Jelle, We have just updated our CONTRIBUTING rules (yesterday in fact!) but we omitted to mention that this service will be launched only from end of week 14. I am sorry about this confusion. Can you submit your Pull Request only after you will be able to approve the CLA as mentioned in the CONTRIBUTING.md file Thank you Christophe

[jelledevleeschouwer]

Hi @CCASTM, Thanks for letting me know! Can I leave the pull request open or shall I close it in the meantime?

[CCASTM]

Jelle, To facilitate our internal management, can you submit again a new Pull Request when you have been able to sign the CLA. Then close this one Thank you Christophe