Example for configuration as power source

[CKraus]

Hi there,
I’m working with a custom PCB that uses an ESP32 as the microcontroller. I need a USB connection to my phone for communication with the controller, and at the same time, I’d like to charge the device through the same connection.
Currently, I’m using a Y-cable to split power and data, but I’m aiming for a more convenient design. I thought the FUSB302 could be a suitable solution, but I haven’t been able to get it working.

I followed your basic cable connection example and replaced the .cc_pull_down() line with .cc_pull_up(USB_TYPEC_CC_STATUS_RP_1_5).

However, my device still charges at only about 100–200 mA. The power supply should support up to 3 A at 5 V.
My understanding was that staying at 5 V wouldn’t require explicit Power Delivery messages, but perhaps that’s not the case for devices like my Samsung Galaxy A56.
Could you provide an example of how to act as a power source including PD?
Thanks, and have a great day!

[nschurando]

Hi @CKraus, just to be sure that I understand correctly, do you want to be charging the phone or the custom PCB?

[CKraus]

Thank you for the fast reply!

I want to charge the phone. 5V/3A stabilized power supply is located on the PCB which powers the ESP and the other components. In future it should be used to charge the phone too.

[nschurando]

Ok, thanks for the clarification. That's a very interesting case, and while I unfortunately don't have the time to provide you with a working example, but I'd be happy to guide you through it.

So, in your case, you're in what the USB specs refers to as independent data-role and power-role assignments.

Historically, before USB Type-C, power and data roles where always tied together: a USB host provided power, and a USB device received power. But because the USB Type-C connector is asymmetrical it allowed for decoupling of the two. And so, new terminology was added:

• Data role : DFP (host) / UFP (device)
• Power role: Source (provides power) / Sink (consumes power)

The specs also introduces terminology for ports that can do both, but for the sake of simplicity, we'll ignore that for now. If you are curious, feel free to browse the section "1.5 Terms and Abbreviations" of the USB Type-C specification.

Here your goal is to have the phone act as a DFP (host) Sink (consumes power). It's perfectly possible, this is what USB Type-C extension dongles do. But it requires a bit of work. The reason being that when USB Type-C devices are attached, they will first use the Data role corresponding to their Power role. To decouple the two, you'll have to perform what's called a DR_Swap (data role swap).

Your board needs to present itself as a Source, because no matter what it will be the one providing power to the phone. This is done very simply, by presenting the Rp pull-up resistors as you have already figured out. By doing so, the phone will assume the Power role of a Sink and start charging. But at the same time the phone will also initially assume the Data role of a UFP (device). By initiating a DR_Swap you will ask the phone to now act as a USB host so that it can talk to your micontroller.

Performing a DR_Swap is done by exchanging messages over USB Power Delivery. Yes, even if you don't negotiate power, this is the way. I'm not going to sugar coat it, implementing the exchange of messages is the hard part, but there is no reason you can't do it, and you're definitely right to look into the FUSB302 because that will give you full control on making it happen. For more info on that, I suggest you have a look at the USB Power Delivery specification.

Feel free to ask if you've got more question. And when do you get it to work, I'll be happy to integrate the example in the library.