Testing Methodology and Documentation

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Test protocol for USB 2.0 Type C Cable

1. Advanced cable tester

Each cable is tested using the Advanced cable tester v2 from Total Phase for several parameters as followed:

  • Continuity and proper wiring of the cable.
  • Signal integrity at 1041 Mbit/s for USB 2.0.
  • Signal integrity at 10070 Mbit/s on each pair (2) for USB 3.1 Gen2.
  • DC Resistance to make sure the DCR is within specs, not too low, not too high.
  • USB PD Rev 2 and USB PD Rev 3 communication protocol.
  • E-marker presence.
  • E-Marker Vendor Data Objects (VODs) correct for USB 3.1 Gen2 spec.
  • Quiescent current in E-marker.

Some problems and issues that we have been noticing so far:

  • DC resistance too high: We often notice higher DC resistances than the allowed values for USB spec depending on how your insert the cable or how the cable is bent etc on mostly Ground cables and Pins. We allow up up to 2 times higher than the max value on some pins. A DC resistance 2 times higher is still a safe value.
  • VBUS through cable set to false: values in E-marker VODs: In reality those values are not check except the max supported current and voltage for PD2 and PD3. Cable is discarded.
  • USB SuperSpeed Signaling set to USB 3.1 Gen 2 (0b010): E-marker is programmed like for a High Speed USB cable but the wiring of the cable corresponds to USB 2.0. Cable is discarded.
  • Signal integrity is too low: Signal integrity is too low meaning the data transfers won’t work propery. Cable is discarded.
  • Quiescent current too high in steady state in the E-marker: The e-marker in steady state is using too much electricity. It can impact power efficiency and dissipates heat from each USB plug. Cable is discarded.

2. External characteristics

The measured characteristics for each cable are the following:

  • Total cable length (cm)
  • Cable length w/o plugs (cm)
  • Cable diameter (mm)
  • Plug 1 type
  • Plug 2 type
  • Cable color
  • Plugs color
  • Plug 1 width (mm)
  • Plug 2 width (mm)
  • Plug 1 thickness (mm)
  • Plug 2 thickness (mm)

Cable diameter, Plug thickness and width are measured with a Mitutoyo 500-170-30 AOS Digimatic Calliper, 0-4” Range, .075” Round Depth.

3. Voltage, Current and Power

We are using a PassMark Power delivery tester connected to a laptop computer Lenovo Thinkpad X1 Carbon 7th
We use PassMark software USBPDTest application to run the test in each supported voltage.

This test shows the max voltage, current and power supported by the cable and the cable ability to support USB Battery Charging protocol.

We are running Voltage vs Current graph at each supported voltage: 5V, 9V, 12V, 15V and 20V. We are also doing a load test at max current and voltage for 30 min.

Setup:

  • Disconnect loopback.
  • In configure change logs to 60 seconds.
  • Run voltage vs Current for 5V, 9V, 12V, 15V and 20V.
  • Save csv file and png file for each.
  • Set voltage to 20v

4. Data transfer

We are using a PassMark Power delivery tester connected to a laptop computer Lenovo Thinkpad X1 Carbon to log the measurements.
Each USB port on the laptop have been tested. You can read the qualification here.

The USB3.0 Loopback is connected to the Power delivery tester in Loopback mode so we can test Data transfer.

The cable is connected to the USB Power Delivery tester and the main USB C port on the laptop. When the cable is connected the USB Power delivery tester detects the speed of the cable. We run a benchmark test using USB3.0Tester application over 3 min with Read then Write for each data packet transfered.

Test mode: Benchmark Test: 3min. Settings: Read then Write.

All USB 2.0 cable should be automatically detected and the test should automatically be done at the maximum detected data transfer speed.

The result is saved in a log file. No error during transfer should be detected. To pass the data transfer test, a cable:

  • Should be autoatically detected as a USB 2.0 cable.
  • No transfer error during test.
  • Max transfer speed should be

4. Cable and plug teardown

As we remove the insulator we can measure

  • Cable AWG

After tearing down the USB Plugs we can make sure that no implant is present in both plugs.

  • Plug 1 implant presence
  • Plug 2 implant presence