TUSB320: Testing issue

Hi Kent,

Kent Chu said:

1. When both the TUSB320L and the external device are configured as DRP, how is the final role (UFP or DFP) determined?

The final role of the TUSB320L depends on what type of connection the TUSB320L makes via the CC lines. If the TUSB320L connects to a source, then the TUSB320L will configure as a sink/UFP. If the TUSB320L connects to a sink, the TUSB320L will configure as a source/DFP.

However, if the TUSB320L connects to another DRP device, then it will not have any guaranteed role. It will configure as either a DFP or a UFP, as both the CC lines of both devices will be toggling each line, causing how it configures to be completely random.

Kent Chu said:

2. Is the current mode detection (via OUT1/OUT2) only available when operating as a UFP? Will there be no output on OUT1/OUT2 when acting as a DFP?

When configured as a DFP, these pins will have no output. There will only be output on these pins when set as a UFP, correct.

Kent Chu said:

3. How is the advertised current determined — by the internal Rp or Rd resistors? In DFP mode, is it possible to advertise 1.5 A or 3 A current levels?

The advertised current is determined by the voltage level seen on the CC lines when set as a UFP:

When set as a DFP, current advertisement can be done, but only via I2C. The TUSB321 should allow this via GPIO.

Kent Chu said:

4. When connecting a smartphone to charge via USB Type-C, the charging process repeatedly starts and stops (intermittent charging).
    I would like to know what the potential reasons for this behavior in my current setup could be.

Can you monitor the ID pin of the TUSB320L and ensure this pin is being pulled down? Additionally, please ensure the ID pin is connected to a voltage switch or some form of controller, as VBUS should only be sent when the ID pin is low.

Is it rapidly starting and stopping charging, or only sporadically, I.E every few seconds/minutes? Are you able to monitor the CC lines and see what the voltage is there? What is the status of the INT_N/OUT3 pin?

Thanks,

Ryan

Hi Ryan,

Thank you for your reply. I still have a few questions.

1. If a DRP smartphone is connected, will the TUSB320L continuously switch between DFP and UFP roles, or will it eventually stabilize?
Also, is it true that the final stable role after each connection could randomly be either DFP or UFP?

Based on my current design (DRP, GPIO mode), is it correct that the maximum advertised charging current is limited to 900 mA when acting as a power source (DFP)? Is it possible to advertise a higher current in this configuration?

Hi Kent,

Kent Chu said:

1. If a DRP smartphone is connected, will the TUSB320L continuously switch between DFP and UFP roles, or will it eventually stabilize?
Also, is it true that the final stable role after each connection could randomly be either DFP or UFP?

If both are DRP, yes, it should eventually stabilize. However, which role both the devices take will be totally random. There are ways you can try to bias which role the TUSB320 will take when set as a DRP if you are using I2C, via the DRP_DITY_CYCLE bit of register 0x09. However, if you stick to DRP, there will be no way to change this, it will stay random.

Kent Chu said:

Based on my current design (DRP, GPIO mode), is it correct that the maximum advertised charging current is limited to 900 mA when acting as a power source (DFP)? Is it possible to advertise a higher current in this configuration?

There is no way to change this in GPIO mode. The TUSB321 however does have this ability in GPIO mode, if that would work better for you: https://www.ti.com/product/TUSB321AI

Thanks,

Ryan