Time Pulse on SARA-R5 GNSS LTE Breakout

[tks]

Has anyone ever seen a time pulse coming out of this device?

I read the comment on the Sparkfun product page that the pulse is too short to see the LED turn on, but I have watched it with a scope (R32 on the schematic), and tried lots of different things to get it to work.

I have set AT+UGPIOC=19,22 which should enable GPIO6 to be the time pulse output (pin 19). That requires a save/reset, which I have done. (The device remembers this setting after a reset, only have to do that once).

U-blox forum person said it needs a lock, or I need to change the UBX-CFG-TP5 config. I changed the config to run the pulse each second for 500ms regardless of a lock… no pulse.

Tried the AT+UTIME instead of AT+UGPS=1,1,3… still no pulse.

So, if anyone has seen a time pulse coming from the SARA-R510M8S, please post your initialization commands.

[TS-Russell]

Moved to GPS forum

[PaulZC]

These notes might help?

https://github.com/sparkfun/SparkFun_u- … MC.ino#L80

Best wishes,

Paul

[PaulZC]

Hi @tks,

It’s a while since I worked on this… I’d forgotten one trick.

The timing pulses are so short that they don’t turn on the FET (Q1 on the Asset Tracker) which converts the 1.8V SARA_TP pulse to 3.3V and drives the TP LED and breakout pin. (See attached.)

If I probe on SARA_TP itself, I can see the TP pulses. They are 1.8V and only 3us (microseconds) wide. But I do see them coming through at 1Hz. (See 2nd attached.)

With wider pulses, Q1 would work just fine.

If you replace Q1 with a faster FET, maybe change R32 too (the 1K Gate resistor), maybe you’ll be able to convert to 3.3V?

I hope this helps,

Paul

[PaulZC]

Here are the degug messages output by the GPRMC example. They show the full list of AT commands used to configure TP and GPRMC. You can ignore the socket close errors - the code is attempting to close any sockets that might have been left open by an earlier example.

09:30:44.654 → Press any key to continue…

09:31:18.083 → init: Begin module init.

09:31:18.083 → sendCommandWithResponse: Command: E0

09:31:18.130 → init: Module responded successfully.

09:31:18.130 → sendCommandWithResponse: Command: +UGPIOC=16,2

09:31:18.177 → sendCommandWithResponse: Command: +UGPIOC=19,22

09:31:18.177 → sendCommandWithResponse: Command: +CMGF=1

09:31:18.224 → sendCommandWithResponse: Command: +CTZU=1

09:31:18.224 → sendCommandWithResponse: Command: +USOCL=0,1

09:31:18.271 → socketClose: Error: sendCommandWithResponse: Command: +USOER

09:31:18.318 → 1

09:31:18.318 → sendCommandWithResponse: Command: +USOCL=1,1

09:31:18.365 → socketClose: Error: sendCommandWithResponse: Command: +USOER

09:31:18.412 → 1

09:31:18.412 → sendCommandWithResponse: Command: +USOCL=2,1

09:31:18.412 → socketClose: Error: sendCommandWithResponse: Command: +USOER

09:31:18.459 → 1

09:31:18.459 → sendCommandWithResponse: Command: +USOCL=3,1

09:31:18.506 → socketClose: Error: sendCommandWithResponse: Command: +USOER

09:31:18.553 → 1

09:31:18.553 → sendCommandWithResponse: Command: +USOCL=4,1

09:31:18.553 → socketClose: Error: sendCommandWithResponse: Command: +USOER

09:31:18.594 → 1

09:31:18.594 → sendCommandWithResponse: Command: +USOCL=5,1

09:31:18.640 → socketClose: Error: sendCommandWithResponse: Command: +USOER

09:31:18.679 → 1

09:31:18.679 → Asset Tracker (SARA-R5) connected!

09:31:18.679 → sendCommandWithResponse: Command: +UGPIOC=23,0,1

09:31:18.726 → sendCommandWithResponse: Command: +UTIMECFG=0,0

09:31:18.773 → sendCommandWithResponse: Command: +UTIME=1,1

09:31:21.184 → sendCommandWithResponse: Command: +UGRMC=1

09:31:21.231 → sendCommandWithResponse: Command: +UGRMC?

[michalisk]

Hi,

Thanks for the posts.

So the pulse width is still 3microseconds?

GPS 1pps is usually 100 miliseconds which is much greater.

Any chance we can increase this?

Regards,

Michalis

[PaulZC]

Hi Michalis,

Unfortunately we are still waiting on a firmware update to resolve this. The back story is available here: https://learn.sparkfun.com/tutorials/lt … leshooting

Apologies,

Paul