Hello

I am using cy7c67200 as a full speed host controller to communiate with GSM modem.

Host is working in co-processor mode and communicating with master CPU via HPI. 
 

TD_ListDone Interrupt is used inform master CPU of transfer completion. 

Most of the time the transmission is fine, but several times a day master CPU informs, that transmission was lost. I took a closer look at this issue using oscilloscope. I revealed that the Host stops generating TD_ListDone interrupt (which isn't disabled in any way in program, also suspend mode is not used). When reading Endpoint Status Register after failure, there is only a NAK bit set (which is OK, beacuse most of the time modem doesn't have data to transfer).

My driver supports error recovery. but new transmission are initialised in TD_ListDone ISR, so when if it fails, whole transmission stops.  Communication is only using Bulk Endpoints and there are no transmission-free time intervals, it;s running all the time. 

Why the Host stops genrating these interrupts ? I cannot find a valid reason for this beahaviour, is it rather software (driver code, wrong host settings) or hardware problem (device hangs bus or sth.) ?

 I am attaching some oscillograms, showing transmision being lost.

Channel 1 (Yellow) - HPI_INT line from EZ-OTG to main MCU,

Channel 4 (Green) - debug pin, set at the beggging of HPI_INT ISR, reset at the end,

M (Red) - differential USB bus signal.

I have found a reason behind transmission being lost. The EZ-OTG on-chip processor is resetting itself, but I dont the cause.

Watchdog timer disabled, reset line decoupled. Is it possible, that electromagnetic radiation from GSM modem antenna disturbs EZ-OTG chip operation ? Modem is located rather close to usb chip on pcb.

 Hi,

Please create a tech support case at www.cypress.com -> Support -> Technical Support -> Create a case. One of our engineers can assist you in this.

Regards,

Gayathri