DRP gadget for Android phone

[SaJe_4790846]

We are designing the gadget that can be connected to the Android phone over USB-C port.

Here are the requirements:

The gadget contains the FTDI USB to RS-232 adaptor ( USB 2.0 )

The Android phone will always be the DFP

The gadget will always be the UFP

The gadget must be the DRP

1. Gadget has the external 5V power connector.

2. If gadget detects the voltage on external 5V connector it should use this 5V to charge the phone and power itself.

3. If gadget does not detect the voltage on external 5V connector it should use 5V coming from the phone to power itself.

4. The role determination must be done when gadget when phone is connected to the gadget.

5. The role maybe swapped if the external power connected/disconnected. (It's just nice to have requirement)

Now the questions:

Q1: What USB PD chip do you recommend to use?

Q2: Do we need to customize chip firmware or it can be done by changing the configuration of the existing one?

Q3: If custom firmware is required what project should be used as a baseline?

Q3.1: Is exchanging of PD messages required for #4 or it cane be done by playing with Rd/Rp?

[Sananya_14 · Accepted solution]

Hi,

1. Please refer to CCG4 and the part that supports docking station i.e. CYPD4236-40LQXIT. If you dont require two ports, and only need PD support on the US port, you could check the single port part CYPD4126-40LQXIT listed in the datasheet. You could also check CCG2, which is a smaller and less integrated part, and check for the parts that support docks.

2. The port role can be set in the configuration with the default port role set in case of a DRP. But the firmware needs to be customized if you want to be a UFP when you are the source since the initial configuration will make the device either a DFP, source or a UFP, sink.

3. For your application, you could refer to the CCG4 Dock solution firmware which is configured to be a DRP port and handles role swap in the firmware to have it as a UFP.

4. The initial role determination will depend on the Rp/Rd terminations as per Type-C specification. If you would like to change the default role that is set, then PD messages can be initiated to change the role.

Best Regards,

Sananya

[SaJe_4790846]

Thanks a lot Sananya for the great pointers. I'll start form here.