Why some USB C cables work, or not, J-Link
5 hours ago
- #Debugging
- #J-Link
- #USB-C
- J-Link Compact debugger has issues with some USB C to C cables, particularly longer ones.
- The problem stems from the device's CC pull-down resistors configuration.
- USB-C specification requires a 5.1kΩ pull-down resistor on each CC line for proper power negotiation.
- eMarked cables (like Thunderbolt or high-power cables) have a 1kΩ pull-down resistor, causing conflicts with the J-Link's design.
- The J-Link connects both CC lines together, leading to incorrect resistance readings when using eMarked cables.
- Workarounds include avoiding eMarked cables, using USB A to C cables, or modifying the device (though this voids the warranty).