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About USB suspend mode in K21 MQX

Question asked by Rahul Hirve on Mar 11, 2016
Latest reply on Mar 17, 2016 by Rahul Hirve

Hi All,


I am using k21 MQX based USB device library for a product which is expected to connect to Android mobile OTG USB port and work.


It takes power from USB OTG of phone, to save phone battery charge I am willing to put K21 in suspend mode when product is not in use and awake on asynchronous USB interrupt.


My observation is, when I am suspending USB bus on K21 using .... and provided phone is in sleep(display off) mode I am getting frequent asynchronous interrupt to K21 USB, this is because SOF/Keep alive on USB coming from Phone OTG? I can see some continues packet traffic on USB bus at this time probed on CRO.


I tried to see how to stop this keep alive/SOF as per my reading it is via USB host I need to do Global/Selective suspend to device connected. But as my host is android phone I am not position do that.


Can anyone help me to understand how can I achieve USB suspend stopping SOF/keep alive frames here?