Resolved! Solved; STM32F437VG: remove AF for a JTAG pin (pin 0x0F) make it be a GPIO.
I use `HAL_GPIO_Init()` to configure my GPIO pins, setting my `GPIO_InitTypeDef` structure initially to zero and then configuring the Pin, Mode, Pull and Speed parameters as I require but leaving Alternate at 0 since I do not want an Alternate functi...