TUSB2E221: CDP handshake event

Hi Vishesh,

Thanks for the answer. They will use TPS2546 for Vbus so it should be fine for Vbus switch.

Best regards
koyo

Hi Vishesh,

Customer checked if CDP is workable but communication isn't resumed because D- is 0V while D+ become 0.6V as expected, so the current is less than 500mA. Could you share possible root cause why D- didn't output 0.6V? 

BC1.2 device is connected to USBA. Customer confirmed the device works appropriately if it's connected to other system and TPS2546 have been used for several years, so the repeater should be the root cause.

Yellow = D+, Green = D-

Expected waveform from TPS2546 DS (D+ and D- are 0.6V, then D- is 0.6V)

Best regards
koyo

Hi Koyo,

How are the EQ and SDA/SCL pins configured? Could you provide the customers schematic?

In order for CDP functionality to be enabled, the SDA pin must be pulled up to 1.8V:

Thanks,

Ryan

Hi Ryan,

SDA/SCL connection is already shown. My understanding is EQ setting is for USB2 PHY so it dosn't impact to CDP.

Best regards

koyo

Hi Koyo,

Where were the SDA/SCL connections shown? I see two picture that don’t load posted previously, is it one of those?

Is the customer able to get any USB2 functionality in their system? Are they able to establish an SDP connection?

Is the customer using the TPS2546 and routing D+/D- through that device between the repeater and the USB2 connector? I see the TPS is also able to provide CDP functionality to a connection, how are the CTL and ILIM_SEL pins configured?

Thanks,

Ryan

Hi Ryan

Here's the image that I attached to the first post. Customer confirmed USB2 eye has passed the criteria. 

I will check the TPS2546 connection later.

Hi Koyo,

I still doesn't see the pictures on my side, it looks like they are not loading correctly: 

Could you help check whether the pictures load on your side, or if they can be reuploaded so I can review.

I would just like to confirm EQ settings but you're correct, it shouldn't have any effect.

Thanks,

Ryan

Hi Ryan

Here's the image of connection. SDA is pulled up by 1.8V and SCL is short to GND.  

EQ0 is pulled up by 1.8V and EQ1/2 are pulled down.

Here is the image that is attached to initial post. D+ (Yellow) become 0.6V as expected but D- (Green) is 0V.

Hi Ryan

Customer keep investigating and CDP is successfully functioned suddenly (Vbus current is higher than 500mA), however there is no secondary detection in D-. Is this waveform same as your expectation?

Hi Ryan

Thanks for the great answer. Customer fully understood.
He thinks the CDP worked due to HW rework impact.

He has another question that CDP is working as expected in both S0 and S4 states but the waveform in S4 is different than he expected. Do you see the reason why D+ and D- are not 0.6V but working correctly?

Waveform in S0. CDP is working and the waveform is same as expectation.
(S0 = Windows system is fully working)

Waveform in S4. CDP is working but the waveform is different.
(S4 = Windows is supended but USB power is ready to supply)

Hi Koyo,

Per the BC1.2 spec, a portable device is able to draw up 1.5V when connected to a CDP, regardless of configuration or rules of suspend:

The waveform in S4 is likely the device following that behavior. Just curious, when windows comes out of suspend, does a BC1.2 handshake occur? Could the customer capture this to check?

And just to double check, the portable device is not being plugged in until after windows goes into suspend, correct?

Thanks,

Ryan