SARA-R5 EXT-INT

Wireless & IoT Cellular
1

Hi, I recently got a SARA-R5 breakout board for the R510M8S, and it is working very well except for two minor issues with the external interrupt:

It looks like multiple transitions on EXT-INT sometimes cause the SARA module to reboot when configured to report timestamps with +UTIME - does the EXT-INT signal need to have a particular shape or time to avoid triggering a reboot?

The other issue I have is that the module does not seem to be able to timestamp correctly when using LTE as the time source. When the GNSS is used for the time source it works fine. This is the basic test sequence I was using:

  • bring up LTE, wait for +CREG:

AT+CFUN=1

OK

+CREG: 6

+CTZV: +44,“23/02/16,12:11:10”

  • set GPIO for EXT-INT and configure +UTIME to timestamp with LTE as the source:

AT+UGPIOC=33,23

OK

AT+UTIMEIND=1

OK

AT+UTIMECFG=0,0

OK

AT+UTIME=3,2

OK

+UUTIMEIND: 3,0,0,0

+UUTIMEIND: 4,2,0,0

…

On interrupt:

+UUTIME: 01/01/2018,00:02:41,565.539570,0.000000000,0

(module reboots)

Is time sync via LTE carrier-dependent?

when using the GNSS as a time source, the +UUTIMEIND indicates sync after a short delay and the interrupt generates a valid time stamp as expected - however the GNSS receiver is not available for positioning until +UTIME is disabled.

Any pointers or info would be very much appreciated :slight_smile:

2

Minor update: Sorry, the GNSS does save NMEA messages while +UTIME is running, so it can be used for positioning at the same time.

3

GNSS Application Note (UBX 20012413) provides the answer. Section 7.3.1

LTE for measuring timing intervals in a sensor:

“Time measured on the device relates only to the events at that device, and cannot be compared to events on other devices”

So, working as expected. When using a GPIO to toggle the EXT-INT, the module does not reboot.