nRF9160 toggle gpio with modem active/inactive state

[khodidas]

Hi,

I am using ncs 1.0.0 and modem fw version 1.0.1. 

I am using PSM mode in my firmware. 

I want to toggle state of one gpio when modem goes in active or inactive state. 

I am using gpio to control sleep mode of LDO powering the nRF9160. 

Is there a way to do this ?

I explored COEX pin and MAGPIO pins usage for this but couldn't find how to use it. 

Regards,

Smitesh Mali

[Simon]

Have you tried using COEX1, I think it does what you are asking about. I can take a closer look at it if you would like to.

Best regards,

Simon

[khodidas]

Hi Simon,

Please take a look at it. 

I read the description of COEX0, COEX1 and COEX2 from below link 

https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf9160%2Fdita%2Fchapters%2Fradio_lte%2Fgnss_coext_if.html

COEX2: Output from the LTE modem to the external device. When active high, indicates that the LTE modem transceiver is turned on.

It seems COEX2 pin is more suitable than COEX1 for controlling LDO sleep control pin. 

But I don't know how to make use of that pin.

I mean , do i need to send any AT command to modem to instruct Modem to toggle this pin when transceiver is 

turned on or off. 

Regards,

Smitesh Mali

[Simon]

I took a closer look at this, and you don't need to send any AT commands in order to use the COEX interface. One thing you should make sure, if you are using the nRF9160 DK, is that the interface pins 6-8 are routed to the COEX interface. However, if you haven't changed anything, this should be done by default (Check out the file boards/arm/nrf52840_pca10090/Kconfig).

To see whether the modem is active or not, attach a 100kΩ pull-down resistor to the COEX2 pin on the P1 connector (see image below), and check its digital value.

I tested it out with the udp_with_psm sample, and configured active time to 1 minute and periodic tau to 90 seconds. I checked the results of COEX2 with a digital analyzer, and it worked as expected:

Best regards,

Simon

[khodidas]

Hi,

Thanks Simon.

Is it possible to toggle GPIO based on the state of this COEX2 pin using DPPI ?

If yes , can you give me any example of it ?

Regards,

Smitesh Mali

[Simon]

I think this can be archived if you physically connect the COEX2 pin to a specific GPIO (e.g. P0.31). Then you can use the GPIOTE module to generate an event when this pin changes value and toggle another GPIO (e.g. P0.30) though DPPI.

COEX2 changes value → GPIOTE event from P0.31 → DPPI → GPIOTE task on P0.31 (toggles)

Best regards,

Simon