Using STM32F407G1-DISCO as a passive USB device to sniff on the bus.

[PPanc.2]

I am using stm32f407g1-disco's High Speed USB core as a USB Device which has no class and is having an exernal ULPI PHY (USB3300) which is connected to the PC. On the other end of the USB3300 I have connected a USB VCP Device.

What I want to do is that let the PC and the USB VCP Device communicate with each other and the signals that I get on D+ and D- lines goes into both USB Devices(stm32f407 and USB VCP device) via USB3300 and I want to read those signals received in stm32f407's USB HS Controller via ULPI PHY but I don't know where that data gets stored at low level.

Could anyone please help me figure this out?

PS: when I monitor the D0:D7 lines of the stm32f407 by a logic analyzer which are connected to the external ULPI PHY, I am able to see the pulses coming on those lines which means that the signal is being received. Am I correct?

[TDK]

The USB peripheral isn't meant to double as a USB packet sniffer / logic analyzer device. If you want that sort of low-level information, you'll need to seek other methods. There are software (free / cheap) USB monitors and hardware (expensive) monitors available.

[PPanc.2]

@TDK​  what I want to do is just watch the communication happening between a VCP device and the PC in between the stm is just listening at the USB bus and transferring the received packets to the UART4.

[TDK]

If you're interested in seeing packets between your device and the PC, USB Monitor Pro will do a decent job at that, among others.

[KnarfB]

If you want to trace the traffic at the PC side, check wireshark: https://wiki.wireshark.org/CaptureSetup/USB