Thingy91 UART External communication

[Adeel]

Hi Dev Team,

I was working on the Nordic Thingy91 and had to establish an external communication of a sensor to the Thingy91 through a UART. 

For this, I was looking into the GPIO's to check which pins can be used for my Tx, Rx, CTS, RTS. 

I found this link : https://devzone.nordicsemi.com/f/nordic-q-a/64742/nordic-thingy-91-pin-name/264224#264224 that talked about using anything between P0.18-P0.25 (MCU_IF0-7).

https://github.com/nrfconnect/sdk-nrf/blob/master/boards/arm/thingy91_nrf9160/thingy91_nrf9160_common.dts#L165-L182

These are said to be connected to the nrf52840 interface. Can I just use these pins for my external UART connection ?

Also, I wanted to know the functions of these Test pads (TP). Can the test pads be also used for UART communication?

If so, how will it be defined in the thingy91_nrf9160_common.dts file. 

Regards,

Adeel.

[JONATHAN LL]

Hi Adeel,


Link to Thingy 91 Test points table. Most of the TP are in use or not really accessible and are there for testing and debugging or connected to sensors in use, in the link you can see all the listed test points and there use on the Thingy91. 

Check out the following links for more information on previous attempts:
https://devzone.nordicsemi.com/f/nordic-q-a/52545/receive-external-data-through-uart-on-thingy-91 
https://devzone.nordicsemi.com/f/nordic-q-a/51355/inputs-via-gpio-on-the-thingy-91 

You can find more info in the hardware description of the Thingy91 and you can download the hardware files(Link to direct download) and including a pdf from our product page.

Regards,
Jonathan

[Adeel]

Hi Jonathan,

Thanks for the links. I referred to the hardware files and finalized the pins thereafter.

I have gone through the links you suggested me. I need modem tracing so I don't want to cut the solder bridges on MC_If[0-7]. That leaves me with only options of TP7 , TP32, TP33 for my uart. 

Could yo verify whether these could be used seemlessly.

Further, could you let me know how I can use P6 pins (originally or nr52840) for nr9160 ?

Regards,

Adeel.

[Adeel]

Hi Jonathan,

Thanks for this infomation, this can be done.

Just one last question before I am clear with this. Will my connection and logging to the LTE Link monitor be disabled if I try to use MCU_IF[] for external communication ? I think by default, UART_0 is for logging and viewing as seen in the autoconf.h file.

Regards,

Adeel.

[JONATHAN LL]

Hi Adeel,

If you keep The uart 0 pins then you will still have logging as normal.

&uart0 {
    compatible = "nordic,nrf-uarte";
    current-speed = <115200>;
    status = "okay";
    tx-pin = <18>;
    rx-pin = <19>;
    rts-pin = <20>;
    cts-pin = <21>; SB7, MCU_IF3
};

if you cut the SB7 then you lose the clear to send pin, you then have to configure logging a different way, and you want be able to use LTE link monitor. 

Regards,
Jonathan

[Adeel]

Hi Jonathan,

Yes I understand that from the schematic.

I will try to use anything between MCU_IF [4-7] for my case then. Hopefully that wont affect my Link monitor.

I just need 1-2 more GPIO's for my use case so I am thinking about this. 

Regards,

Adeel.

[JONATHAN LL]

Hi,

Cutting SB7 will make uart 0 not able to use flow control. you can get away with only rx and tx pin for uart 0, then in LTE Link monitor there is check box you can check to disable or enable flow control. 


Regards,
Jonathan

[Adeel]

Hi Jonathan,

Oh okay, perfect. thanks for the info. I will try that as well :). Thanks for the information on this.

I will try it and let you know if I face any issues.

Regards,

Adeel.

[Adeel]

Hi Jonathan,

I tried using my Thingy91 for external uart communication. 

It all went pretty well except for the receiver pin. Now, I wanted to use any of the pins from MCU_IF[4-7] to test the receiver input..

For that, I was looking to use MCU_IF[7] : P0.25 by cutting the SB11 and I have configured my UART 1 as follows now : 

&uart1 {
	current-speed = <9600>; 
	status = "okay";
	tx-pin = <13>;
	rx-pin = <25>;
	rts-pin = <14>;
};

I just wanted to know if cutting the SB11 would have any have effect on my logging on the LTE Link monitor ?

Regards,

Adeel.

[JONATHAN LL]

Hi Adeel,

Cutting SB 11 should be fine, and it is always possible to revert the effect by soldering the two half's of the SB pad together. 


Regards,
Jonathan

[Adeel]

Hi Jonathan,

Thanks for the answer, will do that. I will cut the solder bridge and try it.

I can connect the Rx wire to any one side of the SB11 pads rite ?

Regards,

Adeel.

[JONATHAN LL]

After cutting SB11 one side is connected to the nrf9160 and the other is to the nrf52.


The right half of the pad is connected to nrf9160(Red highlight). Since you want to use talk to the nrf9160 you should connect the RX wire to the right side of the pad. 

 

Regards,
Jonathan

[Adeel]

Hi Jonathan,

Thanks a lot, I did that and tested it. I actually did it to test another receiver pin. 

I was trying to get an answer from my sensor on my Rx. I see the data on my receive pin and that data is correct. But when I try to read the data on my Link monitor, I get different hex values. 

For example, I see (01 04 04 43 92 08 F6 C8 6B) on my receiver pin through my oscilloscope which is the correct data I need. But when I view the same on the link monitor, I see different values (79 FD F7 F7 EF 29 E0 E0 E0) and I see these values as well in my uart_buf when I debug the code. Its a very strange behavior I am noticing on my Thingy91 as I don't receive the correct bits when I view it, but the correct data is present on the pin when I measure through the oscilloscope. 

For testing reasons, I changed my receiver pin now to P0.25 (previously it was P0.16) but the behavior is pretty much the same. 

I had tested the same thing with the nRF9160DK before and it worked perfectly on the DK. 

I wanted to know what could be the reason with the thingy91 and how can I debug it further ?

Regards,

Adeel.