Greetings,
We have some custom boards/devices with nrf9160. They each hold certificates to communicate with aws-iot. The certificates were flashed using the at_client and LTE Link Monitor Certificate Manager, and are valid till 2050.
Two devices, have, on separate occasions, stopped sending to the cloud. Upon retrieving and examining them, we found that the certificates have disappeared from their memory. The AT command AT%CMNG=1 returns nothing.
The following test function was written:
int certificate_check(void)
{
int err;
err = lte_lc_normal();
if (err)
{
LOG_ERR("lte_lc_normal, error: %d", err);
return err;
}
char ret_buff[1024 * 5];
err = at_cmd_write("AT%CMNG=1", ret_buff, 1024 * 5,
NULL);
if (err)
{
LOG_ERR("Could not get device certs, error: %d", err);
return err;
}
LOG_INF("CERT RESPONSE: %s", ret_buff);
lte_lc_offline();
if (strlen(ret_buff) == 0)
{
return -1;
}
else
{
return 0;
}
}
on a device with certificates, we get this output:[00:00:04.037,597] <inf> main: CERT RESPONSE: %CMNG: 42,2,"02020202020202020202020202020202020"%CMNG: 16842753,1,"0101010101010101010101010101010101010101010101010101010101010101"
on a device without, we get this:[00:00:02.806,793] <inf> main: CERT RESPONSE:
(empty response)
We do not know what circumstances could cause this to happen. We need to make sure the certificates are on the device for its full operational lifetime, and not for them to disappear randomly.
Are there any hardware or software faults/possibilities for this to happen?
Thanks for any ideas or suggestions,
- Tjaž
