lpcware

USB0 is not detected when power to our board is recycled

Discussion created by lpcware Employee on Jun 15, 2016
Content originally posted in LPCWare by krishnapratap.m on Mon Jun 15 23:08:34 MST 2015
Hello

We are facing a difficult issue on our board.

When a USB flash drive is plugged into our board and when we recycle power (+24V, we have converter for +3.3V) to our board, sometimes ( around 1 out of 10 times) drive is not detected. We are not able to identify whether it is a hardware or a firmware issue. Resetting the microcontroller by using RESET pin doesn't fix the problem but if I recycle only the power for microcontroller, USB starts to work.

When we face this issue, PORTSC1_H register has the following value 0x30009501.

Also pin USB0_RREF is left open on the controller instead of the 12k pull down recommended. I could not find the detailed function of this pin in any documentation. Since controller is in BGA package I am not able to connect a resistor and check.

Is there any power sequencing that we need to follow if we have multiple rails on the board?

Please let me know if anybody has come across similar problem.

Thanks & Regards

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