The Wikipedia link quoted below refers to incorrect termination on USB-C cables. Please could you suggest a way (with basic equipment) to test a USB-C cable to see if the correct pullup has been used?


Power issues

Some non-compliant cables with a USB-C connector on one end and a legacy USB-A plug or Micro-B receptacle on the other end incorrectly terminate the Configuration Channel (CC) with a 10kΩ pullup to VBUS instead of the specification mandated 56 kΩ pullup, causing a device connected to the cable to incorrectly determine the amount of power it is permitted to draw from the cable. Cables with this issue may not work properly with certain products, including Apple and Google products, and may even damage power sources such as chargers, hubs, or PC USB ports.

(Source - Wikipedia USB-C)

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    \$\begingroup\$ What is « basic equipment »? You will need a breakout board just to start... \$\endgroup\$ – Solar Mike Mar 16 '19 at 8:05

Use a USB Type-C cable breakout board so that you can readily probe VBUS, CCx and GND. Connect a known voltage value to VBUS (because USB Type-A(m) to USB Type-C (m) cables will have their CC termination pulled up to VBUS) and a known resistor value from CC1 to GND. Use a DMM to measure the CC1 node - if your measurement is yielding the known voltage you're applying, then you've found that this CC pin is actually connected to the VCONN wire. If you measure some lower voltage value then you've discovered the actual CC wire position, and you can deduce the Rp pullup strength.

  • \$\begingroup\$ Any more advice plz? I bought cable on Amazon to connect my laptop to monitor. My laptop gave a BSOD WHEA_UNCORRECTABLE_ERROR. Reading the negative review: "Basically it’s shorted and now draws too much power for the MacBook even Plugged in. Mac throws up an error that’s its drawing too much so it’s disabled. On a lesser machine without power control it could fry it... ie a pixel book. Has happened with other usbc / 3.1 devices". Laptop is going back to manufacturer. amazon.co.uk/gp/customer-reviews/R2X73YZL89HI8V/… \$\endgroup\$ – rupert Mar 20 '19 at 15:56
  • \$\begingroup\$ Is this article still relevant or are USB C/HDMI cables now safe plz? theverge.com/2016/2/4/10916264/… \$\endgroup\$ – rupert Mar 20 '19 at 16:09

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