Set accessory mode fail on Nexus 4

Question

I am trying to learn about Android open accessory, because I am a newbie to ARM programming. So I want to put everything up from bottom, use free open source tools and code.

Compiler: yagarto GNU ARM
NXP LPC1768 demo board: from a company named "waveshare"
USB driver example: NXP hostlite
Android phone is NEXUS 4, Android 4.2.2 version

The reference example NXP hostlite is small and clear. But I can not set accessory correctly in my devised code.

Description:

Inserting detection, and USB reset ---- OK
Read device descriptor ---- OK
Set address to 1, change maximum-pakcet-size to 64 ----- OK
Read protocol, it returns 0x0002 . this means AOA v2 is supported. ----OK
Write identifying string , 5 of them, ----- OK
Set accessory mode. I can see there is a port disconnect and then a port connect interrupt nitification in my Log print-out, ---- so seems this command is also OK
But when I try to read device descriptor now, it returns a Completion code of 5 to me when TD_SETUP is sent out. CC = = 5 means a stall or no response. So I can't judge if the VID, PID is OK or not. ---- Fail

According to AOA protocol, after setting accessory mode, the device would re-enumerate itself.

So my question is: What should I do for re-enumeration?

Wait there until it finish itself; Do I need a delay?
Or reset the device and then read device descriptor again?(I don't think so, because the returned VID/PID are not correct.)
Or any suggestion you would like to share with me.

Set accessory mode fail on Nexus 4

Answers (1)

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