USB Fix:iForce Soft Disconnect

The STM32F404 OTG FS has an internal soft pull-up.

The HW also has one too. So we need to overcome it to force a soft disconnect.

src/drivers/boards/tap-v1/tap_init.c

@@ -154,6 +154,10 @@ __EXPORT void stm32_boardinitialize(void)
 	stm32_configgpio(GPIO_ADC1_IN10);
 
 
+	/* configure USB interfaces */
+
+	stm32_usbinitialize();
+
 	/* configure SPI interfaces */
 
 	stm32_spiinitialize();

src/drivers/boards/tap-v1/tap_usb.c

@@ -55,6 +55,10 @@
 #include "up_arch.h"
 #include "stm32.h"
 #include "board_config.h"
+#include "stm32_otgfs.h"
+
+#define GPIO_DP (GPIO_OUTPUT|GPIO_OPENDRAIN|GPIO_SPEED_50MHz|GPIO_OUTPUT_CLEAR|GPIO_PORTA|GPIO_PIN12)
+
 
 /************************************************************************************
  * Definitions
@@ -78,13 +82,31 @@
 
 __EXPORT void stm32_usbinitialize(void)
 {
-	/* The OTG FS has an internal soft pull-up */
+	/* The OTG FS has an internal soft pull-up.
+	 * The HW also has one too. So we need to overcome it.
+	 * to force a soft disconnect.
+	 */
+
+	/* Issue the Reset to the OTGFS Block */
+
+	uint32_t regval = getreg32(STM32_RCC_AHB2RSTR);
+	regval |= RCC_AHB2RSTR_OTGFSRST;
+	putreg32(regval, STM32_RCC_AHB2RSTR);
+
+	/* Drive the DP Pin Low */
+
+	stm32_configgpio(GPIO_DP);
+
+	/* Release the Reset to the OTGFS Block */
+
+	regval &= ~RCC_AHB2RSTR_OTGFSRST;
+
+	putreg32(regval, STM32_RCC_AHB2RSTR);
+
 
 	/* Configure the OTG FS VBUS sensing GPIO */
 
-#ifdef CONFIG_STM32_OTGFS
 	px4_arch_configgpio(GPIO_OTGFS_VBUS);
-#endif
 }
 
 /************************************************************************************