How to communicate an external module through UART in nRF9160DK?

[Yusuke]

I want to let nRF9160DK communicate with an external module through UART in nRF9160DK

Then I need to assign rx and tx on two pins.

I will use UART0 for printk function so P0.26, 27, 28, and 29 are reserved.

I read page18 in nRF91_DK_User_Guide_v07.pdf and realized that all the pins are already connected to some modules in the DK.

Is it possible to assign some pins as UART tx and rx and connect to an external module? And if possibel, how can yo do it?

Thank you in advance.

[Håkon Alseth]

Hi,

 

Yes, you can override the UART0 pinout using a .overlay file, as explained here:

https://devzone.nordicsemi.com/f/nordic-q-a/44114/continuous-wave-for-nrf9160/174022#174022

 

Note that this .overlay file must be done in both the secure_boot and the non-secure application.

 

Kind regards,

Håkon

[Yusuke]

Thank you for your reply.

I want to use UARTs other than UART0, because UART0 is used for printk func. So how do you let nRF9160 communicate with an external module through UART1, or 2?

[Håkon Alseth]

You can do that similarly as shown in the uart example here, where you alter the main.c to use UART1:

https://github.com/Rallare/fw-nrfconnect-nrf/blob/nrf9160_samples/samples/nrf9160/uart/src/main.c#L31

In prj.conf, you add:

CONFIG_UART_1_NRF_UARTE=y

And the overlay file should then hold your uart1 configuration:

&uart1 {
  status = "ok";
  current-speed = <115200>;
  tx-pin = <1>;
  rx-pin = <0>;
  rts-pin = <14>;
  cts-pin = <15>;
};

The above pin-out goes to the virtual com port on the nRF9160-DK. If you want to connect the pins externally, I'd recommend that you use GPIOs between P0.10 and P0.20, as these are default routed out to the pin lists on the DK.

 

Kind regards,

Håkon

[Yusuke]

Thank you so much for your reply.

> I'd recommend that you use GPIOs between P0.10 and P0.20,

Get it. Then I set uart2 as shown below.

<nrf9160_pca10090.dts>

{

	chosen {
	    ..
        zephyr,uart-wifi = &uart2;
		..
	};
}

&uart2 {
	status = "ok";
	current-speed = <115200>;
	tx-pin = <10>;
	rx-pin = <11>;
};

void main(void)
{
    printk("Hello, World!\r\n");
    uart_wifi = device_get_binding("UART_2");
    if (!uart_wifi) {
    	printk("error\r\n");
	}
	..
}

However, "device_get_binding" does not work well and get error.

build is successful.

Do you know why?

[Håkon Alseth]

Did you add "CONFIG_UART_2_NRF_UARTE=y" to your prj.conf? Are you using the bsdlib in this project? It tries to use UART2 unless you add "CONFIG_BSD_LIBRARY_TRACE_ENABLED=n" to the prj.conf.

 

Kind regards,

Håkon

[Yusuke]

Thank you for your advice!

I added "CONFIG_UART_2_NRF_UARTE=y" to a wrong file. 

Building and Running were successful when I added it to correct file.

However, I can't communicate through UART yet.

Tx pin is P0.10 = Pin 3 in P19.

I checked the waveform of the Pin 3 with an oscilloscope, but there is no signal. 

Do you now why?