Which Analyzer Handles Alternate Mode Protocol Negotiation and DisplayPort Signals?

Question from the Customer:

I'm looking for is a USB-C protocol analyzer for that handling alternate mode protocol negotiation, as well as power measurements.

  • I plan to use USB Type-C cables for delivering power, USB 2.0, and DisplayPort signals to a display.
  • The DisplayPort will be delivered using the USB-C alternate mode.

What can you recommend? Also, DisplayPort protocol decoding is not critical, but that would be a nice feature to have on hand.

Response from Technical Support:

Thanks for your question! Using our USB Power Delivery Analyzer with Data Center Software can support the requirements you that you described.

Monitor and Decode Traffic

Here is a summary of what the Power Delivery Analyzer can monitor:

  • Traffic is monitored is on the CC1/CC2 (configuration channel) pins, while concurrently passing through USB 2.0 and USB 3.1 (up to Gen2) data lines.
  • Power negotiation, including alternate video display modes (VDM) for HDMI, Display Port, and Thunderbolt is monitored on the CC1/CC2 lines and transmitted to the analysis PC via the included USB A to USB Micro-B cable.
  • With the Data Center Software, you can monitor and decode the Power Delivery protocol traffic, including DisplayPort. An example is shown below.
Data Center monitors and analyzes the data captured by the Power Display Analyzer

Power Measurements

Here are the characteristics of the power measurements:

  • Vbus Voltage: measured via an INA231 ADC on the Vbus lines of the USB Type C receptacle connector pins A4, A9, B4, and B9
  • Vbus Current: measured via an INA231 ADC across a 0.015 Ohm shunt resistor between the Vbus input Type C receptacle and the Vbus Type C plug
  • Vconn Voltage:  measured via INA231 ADC on CC2 signal (pin B5) of the USB Type C receptacle. Note - you may need to flip the PDA over if Vconn ends up on the CC1 signal pin (A5).
  • Vconn Current: measured via an INA231 ADC across a 0.015 Ohm shunt resistor between the CC2 (pin B5) Type C receptacle and the CC2 (pin B5) Type C plug
  • CC1 Voltage: measured via STM32's internal ADC – this signal clips at 3.3V, which is useful for "traffic indication".
  • CC2 Voltage: measured via STM32's internal ADC – this signal clips at 3.3V, which is useful for "traffic indication"

We hope this answers your questions. Additional resources that you may find helpful include the following:

If you want more information, feel free to contact us with your questions. You can also request a demo that applies to your application.

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