Some microcontrollers, for example the common STM32 line, claim USB capabilities along these lines:
USB 2.0 OTG HS, that is, USB 2.0 FS/HS device/host/OTG controller, integrating the transceivers for full-speed operation, and featuring an ULPI for high-speed operation: an external PHY device connected to the device is required.
Does that mean there is one USB controller, connected to a FS PHY and with the capabilities(/pins, ULPI) to connect to a HS PHY (one or the other), or does that mean there's one standalone controller+PHY couple capped at full speed and something else entirely that would manage an external PHY, which would mean double USB capabilities when using an external PHY ?
The wording of that resource makes me believe the former, but datasheet feature summaries have me believe the latter:
Advanced connectivity
- USB 2.0 full-speed device/host/OTG controller with on-chip PHY
- USB 2.0 high-speed/full-speed device/host/OTG controller with dedicated DMA, on-chip full-speed PHY and on-chip Hi-speed PHY or ULPI depending on the part number
This question Connecting two USB DP/DM also leaves me unsure: "The only time the FS port will be used is during dfu where the ulpi won't be working." ?
I'd love a clarification. Hopefully the underlying concepts aren't STM32 specific.
Best Answer
In on some of their EVAL boards they put a PHY and an OTG, I am 99% sure that you can run both at the same time.
I interpret this statement (From the stm32f750v8 datasheet) to mean that you can have two USB connections at the same time, but the second one requires a phy.
I have seen STM32H7's or F7's with two D+ D- pairs on them (can't remember where), so I assume they have two usb phys built in.
If it says (with the ULPI) then you'll need a PHY for two USB's
Also if you want the full 480Mbits, you'll need a PHY.