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.

[JONATHAN LL]

Hi,

P6 is connected to nrf52840, to get to those pins you can communicate between nrf52840 and nrf9160. Setting up a passthrough on the nrf52840 where you get the UART from sensor to nrf52840, and UART from nrf52840 to nrf9160. Look at the connectivity bridge example for guidance on how to set it up. 

 

Adeel said:

That leaves me with only options of TP7 , TP32, TP33 for my uart. 

 Those are the only access points to a nrf9160 GPIO. 


May i ask what sensor you are connecting since it is using UART and not i2c or spi?

Regards,
Jonathan

[Adeel]

Hi,

I am connecting a AST-3P device that works on Modbus protocol. So, I require a RS-485 communication through UART , using Tx, Rx, RTS, CTS. I can pin up RTS/CTS together to 1 pin so I was looking for 3 pins that I could use directly for Tx, Rx, RTS/CTS. 

To start off, I have configured this overlay file (thingy91_nrf9160ns) in my project.

&uart1 {
	current-speed = <9600>; 
	status = "okay";
	tx-pin = <13>;
	rx-pin = <16>;
	rts-pin = <10>;
};

I also changed the thingy91_nrf9160_common.dts file with the same pin configuration using uart_1.

Is this the only changes required to enable uart_1 in the thingy91 board ?

Regards,

Adeel.

[JONATHAN LL]

Hi Adeel,

Make sure that the voltage from the AST-3P does not exceed the voltage on the thingy91 capability's when connecting the two over RS-485.

Yeas that should be all.

Regards,
Jonathan

[Adeel]

Hi Jonathan,

Yes. I have taken that into account that the voltage should not exceed 1.8V which is what thingy91 GPIO's work with. 

I was trying to look for more GPIO's that I could work directly with nrf9160. Are all the MCU_IF [0-7] used for modem tracing (or) can I use some pins of it without disabling the modem trace ?

Regards,

Adeel.

[JONATHAN LL]

Hi Adeel,

Do you have a eternal debugger? or do you plan to update the Thingy91 device with programmer app?

another thing, it seems that you are in need of GPIO's so i would highly recommend using a nrf9160DK instead of a Thingy for development and testing external sensors. 


The MCU_IF pins are used to communicate between the nrf9160 and the nrf52840 is the interface that connects the nrf9160 to usb. If you start cutting the SB7 to SB11 you wont have full uart 0 and 1 support.

in the thingy91_nrf9160_common.dts file you can see that these pins are used to uart. if you can get away using only 1 then you can cut out uart1

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

&uart1 {
	current-speed = <1000000>;
	status = "okay";
	tx-pin = <22>;
	rx-pin = <23>;
	rts-pin = <24>;
	cts-pin = <25>;
};

If you cut all or any of the SB 7 to 11 then you will have to edit the board files also.

Regards,
Jonathan

[Adeel]

Hi Jonathan,

I have a nrf9160DK and I am using that as an external debugger. I have used the same sensor and was able to communicate it with the nrf9160DK, but our main requirement is to use the Thingy91 platform for further development. That is why I was in need of more GPIO's. 

Yes, for now I am using UART_1 by modifying the overlay file. Is there also UART_2 as was the case in nrf9160DK that I could use ? I can see only uart_0 and uart_1 in the dts file.

Regards,

Adeel.

[JONATHAN LL]

Hi Adeel,

Adeel said:

Is there also UART_2 as was the case in nrf9160DK that I could use ?

No, not on the thingy91 platform. 


The Thingy 91 is not designed for developing additional sensor on and is more of a closed solution for testing systems and the onboard sensor. If you are looking for a small form factor solution the Icarus or Feather (more information here) solutions might be more relevant.  

Since you have a nrf9160DK then you should be able to do logging over RTT, this way you can use more of the MCU_IF if needed but you need to have the nrf9160DK connected. 

Regards,
Jonathan

[albdom]

Hi!

I have the same problem, you can only use two instances of the UART on the nrf52840, UART0 and UART1.

My question... is the UART0 between nrf52840 and nrf9160 needed to log if it is wanted via RTT with the nrf9160DK connected?

Regards,
Alberto

[JONATHAN LL]

Hi Alberto,

There is a switch SW2 that you can use to select between nrf91 and nrf52 on the thingy.


UART is not needed when using RTT. just make sure that the switch is locked in the nrf9160 position when you want to log RTT from nrf9160. 

Regards,
Jonathan

[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.