Implement full DFP support
Expected Behavior
The circuit should be able to switch between the external voltage on the screw terminal and 5V to implement the DFP (down facing port) functionally of the USB PD standard.
Current Behavior
On the board is currently no circuitry to switch between the VBUS voltage and the voltage of the USB Type A connector. You could only disconnect those two signals by not placing the SMD jumper and externally switch between different voltages, depending on the negotiation with the UFP.
Possible Solution
- Add MOSFETs to switch between the 5V VBUS voltage of the USB Type A port and the voltage of the screw terminal
- Add the ability the measure the voltage of all connectors to dynamically switch between the different roles and prevent short circuits
- Generate 5V on board to use the board as a PD power supply w/o a USB Type A connection
- The same converter could be used that currently generates the 3V3
- the 3V3 for the STM32 could be generated with a LDO regulator from the 5V of the buck converter