Hi Guys,

I am porting usb host tty device driver on uboot. I just use usb usb_bulk_msg to communicate with modem. I met the following problems.

Could you please help me resolve the following issue? Thanks in advance.

When I use usb usb_bulk_msg to connect one USB modem, send one AT command (e.g. AT) to Modem, and can receive a responding message, e.g., OK and so on.

But When I want to use usb usb_bulk_msg to receive the RING command from modem without sending any AT command to modem, I could not receive any data from modem, even NAK, STALL cannot be received. Then program timeout. But if I send ATA, the can answer the incoming call.

I do not know how to receive the data from modem, when host did not send AT command to modem.

Even I use usb_submit_int_msg, I only receive NULL.

WHY?

Thanks & Best regards,

Steven Wang