TUSB320LAI: How to enable USBC audio and charging at the same time?

Hi Pakha,

There are two options for audio over USB-C. 

There is Digital:

- uses superspeed lines (TX1, TX2, RX1, RX2). Audio is convert to USB protocol and sent over USB

There is Analog:

- This uses a specific audio accessory mode. This is muxing the audio lines over the SBU and the USB2 lines. This is better defined in the USB-C specification.

What kind of audio are you trying to pass?

Will the TUSB320 be in UFP or DFP?

TUSB320 will be DFP. Our devices also have a charging-out function. When the TUSB320LAI is recognized as a receiver, is it possible to charge externally at the same time?

Hi Shane,

I still have a little bit confuse. Audio accessory only can be read from TUSB320. It cannot be manually set

Below is our requirement. Is this possible to achieve it?

If only one method can be supported at a time, is there a way to renegotiate the USB port via an I2C command? Or the negotiation only can be happened while usb plugging or unplugging.

Hi Pakho,

Pakho said:

Below is our requirement. Is this possible to achieve it?

Yes, audio accessory mode can support up to 500mA of current from the type-C receptacle:

Audio accessory mode is for adapters that convert the USB-C cable to a 3.5mm audio jack. I do not see where the 3.5mm jack is in your block diagram. Are you only connecting the DUT to a phone/tablet/laptop over USB-C or is there a 3.5mm audio connection between them?

Best,

Shane

Hi Shane,

Thanks for reply. There is only C to C cable connection. No 3.5mm audio connection.

Please also reply this one. Thanks in advance.

If only one method can be supported at a time, is there a way to renegotiate the USB port via an I2C command? Or the negotiation only can be happened while usb plugging or unplugging.

Hi Pakho,

You can re-negotiate the USB connection by toggling the DISABLE_TERM register. Toggling this in I2C will re-enumerate the connection even when the USB is constantly attached.

Unplugging and re-plugging will also re-negotiate the connection.

Pakho said:

There is only C to C cable connection. No 3.5mm audio connection.

If there is no 3.5mm audio connection, then you are likely using USB-C digital audio (not audio accessory mode). Please see appendix C of the USB-C spec for more info on this:

Best,

Shane

Hi Shane,

Thank you for your careful reply.

Yes, when we enable the USB-C audio feature, the accessory is "Attached.SNK (UFP)" and the accessory is "No accessory attached".

This is our design. If we enable the USBC audio feature, we need to set the TUSB320 to UFP. At this point, the USB_VBUS from the phone or PC or tablet is above 5.0v, and when the iPad is connected, it goes to 5.3v.

Therefore, if we want to charge our mobile or PC or tablet. The VBUS should be higher than 5.3V and the charging current should also be at least higher than 500mA. Is that so?

Hi Pakho,

If the TUSB320 is set as a UFP, you cannot provide power to the attached phone/ipad. UFP can only receive power from the attached device, not provide power. I do not recommend trying to provide power by increasing the VBUS voltage on the UFP side of the connection.

If you want to provide power to the Ipad/Iphone, you should set the TUSB320 to DFP mode. Since you are using type-C digital audio (not accessory mode), you can set the current advertisement up to 3A.

I have a couple questions about your system:

Pakho said:

If we enable the USBC audio feature, we need to set the TUSB320 to UFP

1. Why do you need to set the TUSB320 as a UFP to enable the audio feature? Audio should pass regardless of the UFP/DFP configuration of the TUSB320.

2. Is J7 the USB-C connector on your board? This is not a standard USB-C connector and I am unsure how you pass audio through this connector.

Best,

Shane

AFAIK, UFP is unable to initiate data transfer; It can only respond to requests from downstream ports (DFPs). The initiator of the data transfer is usually a DFP, such as a PC or charger.
However, the UFP can request a role switch via the CC pin, changing from UFP to DFP, allowing it to initiate data transfers. This is typically achieved through the USB Power Delivery (PD) protocol, which allows devices to negotiate roles and power allocations.
If a USB audio device can both receive audio data from and charge your phone, it needs to support USB Type-C and USB Power Delivery (PD) protocols.
So back to this design, is it necessary to add an additional PD chip to meet the demand?