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 for 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.
Thanks & Best regards,
Steven Wang