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USB Superspeed Peripherals

roji_4156651
New Contributor

I develop a firmware. The firmware works perfectly on the CX3-based module. The module can be enumerated as USB3.0 device.But when I replace the CX3 board with my own board(I design and make according to the CX3 design schematics.And I recheck the design schematics, it should be ok.), the module can not be enumerated as USB3.0 device. The following figure is the USB trace.How can I fix the problem?

3.0.jpg

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1 Solution
JayakrishnaT_76
Moderator
Moderator

Hello,

I see that you have shorted the superspeed lines from the Type C receptacle. This reduces the signal quality. This is the reason why the device falls back to USB 2.0. Please refer to the section 2 of the following KBA

Designing FX3™/CX3-Based USB Type-C Products - KBA218460

Please use the above KBA and route the superspeed lines using a MUX.

Best Regards,

Jayakrishna

Best Regards,
Jayakrishna

View solution in original post

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roji_4156651
New Contributor

I change the interface to type C instead of type B. I think this should not matter.

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JayakrishnaT_76
Moderator
Moderator

Hello,

Please share the schematic of the custom board with us so that we can debug the issue.

Best Regards,

Jayakrishna

Best Regards,
Jayakrishna
roji_4156651
New Contributor

Our schematics diagram is as follows:        Thanks!3.png1.png4.png2.png

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JayakrishnaT_76
Moderator
Moderator

Hello,

I see that you have shorted the superspeed lines from the Type C receptacle. This reduces the signal quality. This is the reason why the device falls back to USB 2.0. Please refer to the section 2 of the following KBA

Designing FX3™/CX3-Based USB Type-C Products - KBA218460

Please use the above KBA and route the superspeed lines using a MUX.

Best Regards,

Jayakrishna

Best Regards,
Jayakrishna

View solution in original post

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roji_4156651
New Contributor

We split the superspeed lines from the receptacle. And we add a pull-down 5.1K ohm resistor at the pin CC1(A5) according to the KBA218460. This solution should be reasonable. But the module is still enumerated as USB2.0 device. What could be the cause?

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JayakrishnaT_76
Moderator
Moderator

Hello,

Please send the updated schematic of the Type C receptacle section. Also did you use the MUX to select the superspeed lines and how did you select the correct pair of superspeed lines?

Best Regards,

Jayakrishna

Best Regards,
Jayakrishna
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roji_4156651
New Contributor

Only USB type-c interface section has been changed ,as shown below:

5.png

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JayakrishnaT_76
Moderator
Moderator

Hello,

Please let me know whether you are using Type C receptacle or Type C Plug for the product.

Best regards,

Jayakrishna

Best Regards,
Jayakrishna
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roji_4156651
New Contributor

We are using  Type-C receptacle  for the product;

6.png

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JayakrishnaT_76
Moderator
Moderator

Hello,

Then please connect the pins of the receptacle according to section 2 of the KBA mentioned above.

pastedImage_0.png

You need a mux to switch the superspeed lines. You cannot leave one pair of lines disconnected.

Best Regards,

Jayakrishna

Best Regards,
Jayakrishna
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roji_4156651
New Contributor

Hi,JayakrishnaT:

         As depicted in KBA218460, "As shown in the Figure 2, the two pairs of each USB data line from the USB Type-C receptacle is connected to the multiplexer. From the multiplexer, a single pair of USB data lines is connected to FX3. The MUXSEL line is controlled through an output GPIO of FX3 to select the correct pair of USB SuperSpeed lines. The logic of selecting the correct pair of USB SuperSpeed lines is implemented in FX3 firmware."

         In the description it says that the logic of selecting the correct pair of USB SuperSpeed lines is implemented in FX3 firmware. Could you tell me how the FX3 firmware knows which pair of USB SuperSpeed lines to select.

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JayakrishnaT_76
Moderator
Moderator

Hello,

Please refer to the following thread to understand how the MUX selects the right pair of superspeed lines.

CX3 USB-C MUX Not connecting at high-speed

Best Regards,

Jayakrishna

Best Regards,
Jayakrishna
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