I try to use LPC546xx High speed USB1 port to connect with Lenovo T420 by ISP mode. That have chance to fail ( unknow device ). Our LPC546xx's USB1 is pass eye diagram.
The following is LPC546xx USB1 eye diagram test.
However, Lenovo T420 always can detect hard disk thought High speed USB 2.0 mass storage. By the way I also serial USB cable to High speed USB 2.0 mass storage to simulate LPC546xx's situation.
I found LPC546xx USB1's high speed detect handshake have some abnormal waveform.
The following is LPC546xx high speed detect handshake waveform. ( Blue is D+, Yellow is D- )
The following is High speed USB 2.0 mass storage with USB cable. ( Green is D+. Purple is D- )