Hello all there,
I am currently exploring a design based on a STUSB1602 USB PD-Controller.
The accessory would have to behave like a classic USB HUB, provided with a Type-C receptacle - to sink power - and a Type-C connector - in DRP configuration to source/sink power to/from device.
- For the Type-C receptacle - the "charger" port - I selected the STUSB4500 stand-alone USB PD Controller with a PDO contract of 5V/3A preloaded as a default configuration via the NVM.
This path will provide power to change the Type-C connector configuration (UPF->DFP).
- For the Type-C connector, the default role must be of course as a UPF that sinks power from the connected device (that could be a Laptop, an iPad Pro and so on).
As soon as the requested voltage is available through the charging port, the configuration must be switched to to a DFP, thus providing power to the device.
I chosen the STUSB1602 as a DRP controller.
I am currently addressing some issues while trying to understand the final design that I will build:
1. About the STUSB1602, if I read correctly from the data sheet, to request a Power Role Swap I must send the command via the I2C interface, thus invalidating the hypothesis to ship a design without an MCU.
Is this correct? And, if yes there is some firmware/driver code to test out the Power Role Swap functionality?
2. I will buy the P-NUCLEO-USB002 kit, but it's currently unclear to me if I can emulate the Power Role Swap using the provided hardware. Maybe configuring one STUSB1602 as a sink and the other as a DRP controller?
3. If I correctly understood the P-NUCLEO-USB002 expansion board schematic, all the power paths are managed by the MCU, so the point 2 could be feasible.
4. The main Role of my accessory/hub must be to source power to the host if an external supply is attached, but it must act as a USB Device (it will be connected to an audio card and a STM32 Low Power MCU via an USB 2.0 hub) so I think the DFP/UFP nomenclature related to USB Data Path is a bit improper: it should be a "sourcing/sinking device". Is that the behaviour of "Data role swap"?
Thank you in advance and sorry for my lengthy questions,
Luigi
