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LPC546XX USB failed to apply 45Ω HS resistor

Question asked by on May 22, 2019
Latest reply on Jul 21, 2019 by


  I use lpc546xx as a usb composite device. And I've found one of my developing board failed in USB enumeration(I have several  the same boards) , but the rests work fine(with the same fireware).

  And then I used usb analyzer tools tracing USB Packets, and found that lpc546xx failed during RESET stage.

  Then I've used OSC to view USB D+/D- wave. After Reset, the device sended Chirp-K, and then Hub sended K-J pairs; but The device doesn't apply 45Ω HS resistor termination to D+/D-.  So K/J pairs remains 800mV, and this maybe the reason USB device failed in enumeration.

  So, my question here:

  1. Is there any register control the 45Ω termination directly in lpc546xx ? So I could test the termination without USB HUB;

  2. I've checked the PCB routing and connection, D+/D- are well connected to MCU pins; and mcu internal 1.5KΩ pull-up resistor also works well. So HighSpeed terminals failed to apply could be mcu IC problems?

 Thanks for your advice !

  3. I've checked the Errata Sheet.  It says device can't see KJ Chirps (page 12) . Could this be the reason of enumeration failure?   The Errata also point out the SDK had made a soft walk-around. Would you please tell me the places of corresponding modification in SDK? I want to be sure if I implemented the modified SDK.


Ps: OSC signal wave (Green for D+ , Yellow for D-)