STM32F7508 - Problem with VBUS and ST-Link (UART1)

Roman REITER · ‎2022-10-30

I would like to use the otg_fs_vbus interface of the STM32F7508 Discovery to plug in a USB stick. When I activate VBUS in CubeMX, the board no longer boots up. The reason for this is that pin PA9 is used for the ST link (UART1) and the vbus. Both at once doesn't seem to work. Does anyone have an idea to solve this?

KDJEM.1 · ‎2022-10-31

Hello @Roman REITER,

By default, OTG_FS_VBUS is driven by the software and not by the alternate function of the STM32F750N8H6 (R64 = ON, R63 = OFF, R58 = ON and PA9 = VCP_TX (Virtual Com Port) and PJ12 = OTG_FS_VBUS).

To use the alternate function OTG_FS_VBUS of the STM32F750N8H6, it is needed to have: R64 = OFF, R63 = ON, R58 = OFF. In this configuration, VCP_TX is no longer available and PA9 = OTG_FS_VBUS, PJ12 = not connected.

For more explanation, I advise you to take a look at the UM2470 and precisely Appendix A section.

Thank you for your contribution.

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Thank you

Kaouthar

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Roman REITER · ‎2022-10-31

Hello @KDJEM.1

I saw this, but i don't know what should i do.

I think the alternate function should be code-auto-generated when i activate the vbus, but it generates a wrong code.

What shall i do? Should i set PJ12(=R58) and PA3(=R64) to Output/Low and PA9(=R58) to Output/High?

AScha.3 · ‎2022-10-31

for connecting an USB stick, you power the board anyway, so do not set VBUS.

make host mass storage class...software.

then plug in stick, will work.

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Roman REITER · ‎2022-10-31

I tried that. Have DP5 set to Output/LOW. However, the USB stick only gets power for a short time when the board is started. Only when I activate VBUS does the USB stick get power, but the LCD remains black.

KDJEM.1 · ‎2022-11-01

Hello @Roman REITER,

To use the alternate function OTG_FS_VBUS of the STM32F750N8H6 discovery, it is necessary to remove the R64 and R58 resistors and solder the R58 resistor in the PCB. In this case VCP_TX is no longer available, PA9=OTG_FS_VBUS, PJ12 is not connected.

Thank you

Kaouthar

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AScha.3 · ‎2022-11-01

try:

set PD5 lo. (is this small test program or part of something big? )

or can try:

solder close sb18. and JP1 5-6 set on.

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Roman REITER · ‎2022-11-14

I unsoldered R64 and R58, also I soldered R63 > 2M (used the old R64). PD5 ist Output/Low. After that I have 3.3V at the USB port. But there are two things that don't work:

1st: When I change the PA9 pin from UART1 to PB6 -> the board does not start

2nd: If I don't change the PA9 pin of UART1 -> the board starts, but when I plug in or unplug the USB stick, the state doesn't change. so i can't mount the usb-stick. So, it doesn't work.