RC7620 unresponsive to QMI (sometimes)


I am using libqmi APIs to configure/communicate to our RC7620 modem mounted on RED mangOH from Sierra wireless. It is found that sometimes, the modem becomes totally unresponsive. The only way out seems to be to reset the modem.

Manufacturer: Sierra Wireless, Incorporated
Model: RC7620
Revision: SWI9X07H_00.08.24.02 f90cbd jenkins 2022/03/21 03:47:54
IMEI: 353634110124095
FSN: 7Q0464853612B0


Very rarely, we also have QMI_CORE_ERROR_TIMEOUT errors. Since this happens very rarely, like once in a 100 reboot tests or so, it is hard to understand whats happening in the modem that makes it either completely unresponsive or timeout on random QMI APIs like qmi_client_nas_get_operator_name(), qmi_client_dms_swi_get_current_firmware() etc…

If I try the same application with a 4G dongle (DMW-222), which is also QC based, I don’t get any such issues in over 1000 trials. Any suggestions regarding how this can be solved are highly appreciated.

If you need any other info that can help through more light on this issue, kindly let me know.


When it is unresponsive, can you communicate with AT command?

I don’t remember trying AT commands. It doesn’t respond to any more QMI APIs. But I can check about AT commands and get back