Few Questions on nRF9160: Thingy:91 and Dev Board

[Lakshminarayana K N]

Hi,

I have few question on nRF9160 Thingy:91 and Dev Board.

1.    From the schematic, I see that have used SP8T Switch from Antenna Feed pin (GPS and LTE) to the SIngle Antenna (Fractus).

When we initially turn on GPS and read the GPS Fix data(TTFF:30 seconds as per the data sheet) and Then switch off GPS section and Turn ON LTE and send the data.

If we turn on GPS again immediate after sending the GPS Fix data(meaning Turn off LTE and Turn ON GPS) Will it take again 30 seconds to get the GPS Fix data Or it'll be quicker?

2.   Is the LNA for GPS  required?

If we're using Separate external antenna for GPS and LTE CAT-M1/NB1 what's the use of Switch(U33 and U34) we can directly connect to the Antenna Feed point to the Module's GPS Feed point(with / Without LNA) right?

https://www.nordicsemi.com/-/media/Software-and-other-downloads/Dev-Kits/nRF9160-DK/pca10090_schematic_and_pcb_rev085.pdf

3. Could you please give me example of COEX2 (pin 91)?

4. Are there any limitation on Max duration of sleep mode on nRF9160?

5. May I know the Layer stack up details of Thingy:91?(Signal,GND,GND Signal OR Signal,GND,PWR,Signal?)

Thanks.

[Håkon Alseth]

Hi,

 

 

If we turn on GPS again immediate after sending the GPS Fix data(meaning Turn off LTE and Turn ON GPS) Will it take again 30 seconds to get the GPS Fix data Or it'll be quicker?

 It has the almanac and ephemeris at this point. Next fix will be faster.

Is the LNA for GPS  required?

 Yes, an LNA is required.

Could you please give me example of COEX2 (pin 91)?

 You should use COEX0. here’s the AT command in C: https://github.com/NordicPlayground/fw-nrfconnect-nrf/blob/master/samples/nrf9160/gps/src/main.c#L30

Are there any limitation on Max duration of sleep mode on nRF9160?

 No, if the application you develop sleep in a very long period, that should be fine. Are you thinking of eDRX or PSM periods (ie: LTE network sleep periods), or the sleep period local to the CPU?

May I know the Layer stack up details of Thingy:91?(Signal,GND,GND Signal OR Signal,GND,PWR,Signal?)

The HW design files can be downloaded from https://www.nordicsemi.com/Software-and-tools/Prototyping-platforms/Nordic-Thingy-91/Download#infotabs

The main ground plane is at inner layer 1. So Signal, GND, Signal and ground, Signal. Power is mainly routed at the bottom layer. 

 

Kind regards,

Håkon

[Lakshminarayana K N]

Hi,

Thanks for your reply.

"Yes, an LNA is required." Usually module's have inbuilt LNA right? In this case it's not right?

"  No, if the application you develop sleep in a very long period, that should be fine. Are you thinking of eDRX or PSM periods (ie: LTE network sleep periods), or the sleep period local to the CPU? " -  About the LTE Network sleep mode mainly PSM and eDRX mode. In case of eDRX mode, what's the maximum duration it can be in saving mode? and also Is there way where we can completely turn off LTE part(not PSM) and only main CPU and GPS part?

" The main ground plane is at inner layer 1. So Signal, GND, Signal and ground, Signal. Power is mainly routed at the bottom layer. "   Yea the reason because I do see RF Layout is done in both Top and Bottom Layer.

In case of  Bottom Layer, For the RF Transmission line reference plane is L2 or L3?

Thanks.

[Håkon Alseth]

Hi,

 

Lakshminarayana K N said:

Usually module's have inbuilt LNA right? In this case it's not right?

 An external LNA is required with the nRF9160.

 

Lakshminarayana K N said:

About the LTE Network sleep mode mainly PSM and eDRX mode. In case of eDRX mode, what's the maximum duration it can be in saving mode? and also Is there way where we can completely turn off LTE part(not PSM) and only main CPU and GPS part?

 For the sleep periods, please see this post: https://devzone.nordicsemi.com/f/nordic-q-a/48027/edrx-mode-psm-mode-sleep-mode-standby-mode-active-mode-power-consumption

Note that you can ask for a given interval, but it is the network that sets this. This means that you cannot expect to get exactly the timing parameters that you ask for.

As for turning off and on the modem, that is done using AT+CFUN: https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/mob_termination_ctrl_status/cfun_set.html?cp=2_1_3_0_0

 

Lakshminarayana K N said:

In case of  Bottom Layer, For the RF Transmission line reference plane is L2 or L3?

The transmission line has a GND reference to the closest layer. Note the cut-out (keep out area) underneath the components around the U2 device.

 

Kind regards,

Håkon

[Lakshminarayana K N]

Hi,

Thanks for the inputs.

I need one clarification for this:

" If we're using Separate external antenna for GPS and LTE CAT-M1/NB1 what's the use of Switch(U33 and U34) we can directly connect to the Antenna Feed point to the Module's GPS Feed point(with / Without LNA followed by matching nw ) right?

https://www.nordicsemi.com/-/media/Software-and-other-downloads/Dev-Kits/nRF9160-DK/pca10090_schematic_and_pcb_rev085.pdf  "

[Håkon Alseth]

The point of these switches are to allow external antenna or the use of on-board antenna.

Note that you are looking at an old version of the DK, where the latest is v0.10.2: https://www.nordicsemi.com/Software-and-tools/Development-Kits/nRF9160-DK/Download

 

Kind regards,

Håkon

[Lakshminarayana K N]

Hi,

One question on Fractus antenna though TRIO mXTEND has 2 ports (which can be used for GNSS and NB-IoT/CAT-M) May I know the reason why only single port being used?

[Håkon Alseth]

Hi,

 

Lakshminarayana K N said:

One question on Fractus antenna though TRIO mXTEND has 2 ports (which can be used for GNSS and NB-IoT/CAT-M) May I know the reason why only single port being used?

I checked this with the HW designer, and Fractus did the implementation around the antenna. It could be just a coincident, but I'd recommend asking Fractus to hear if they can comment.

 

Kind regards,

Håkon