GpioMcuRemoveInterrupt sets GPIO pull-up/pull-down registers to random uninitialized memory

[nfroggy]

This happens at least on the NucleoL476 example board implementation. I had a quick look at the other STM32 examples and it appears to happen there too. The issue is that GpioMcuRemoveInterrupt doesn't initialize the Pull field in the GPIO_InitStructure struct. It then calls HAL_GPIO_Init, which bitwise ORs the uninitialized Pull field with the GPIO PUPDR register, causing random values to be written to the pull-up and pull-down registers.

Our internal fix was to zero-initialize the struct to make sure that nothing was being changed in the PUPDR register:

void GpioMcuRemoveInterrupt( Gpio_t *obj )
{
    if( obj->pin < IOE_0 )
    {
        // Clear callback before changing pin mode
        GpioIrq[( obj->pin ) & 0x0F] = NULL;

        GPIO_InitTypeDef   GPIO_InitStructure = {0};

        GPIO_InitStructure.Pin =  obj->pinIndex ;
        GPIO_InitStructure.Mode = GPIO_MODE_ANALOG;
        HAL_GPIO_Init( obj->port, &GPIO_InitStructure );
    }
    else
    {
#if defined( BOARD_IOE_EXT )
        // IOExt Pin
        GpioIoeRemoveInterrupt( obj );
#endif
    }
}