Configuring UART_1 for nRF9160

[Adeel]

Hi Dev Team,

I was working with the nRF9160 and started off with the basic UART sample found here : https://github.com/Rallare/fw-nrfconnect-nrf/tree/nrf9160_samples/samples/nrf9160/uart

I wanted to configure the UART_1 to connect to an external sensor, and I followed some links : https://devzone.nordicsemi.com/f/nordic-q-a/45476/connecting-uart1-to-a-periph-on-nrf9160-dk/178988#178988, https://devzone.nordicsemi.com/f/nordic-q-a/57199/using-the-nrf9160-to-send-and-receive-data-over-rs485-using-uart and changed the prj.conf file and the overlays file. 

prj.conf:

CONFIG_NEWLIB_LIBC=y
CONFIG_LIBLIGHTMODBUS=y


CONFIG_SERIAL=y
CONFIG_TRUSTED_EXECUTION_NONSECURE=y
CONFIG_UART_INTERRUPT_DRIVEN=y
CONFIG_MAIN_STACK_SIZE=4096

CONFIG_COMPILER_OPT="-DNRFX_UARTE_ENABLED=1 -DNRFX_UARTE0_ENABLED=1"


CONFIG_UART_1_NRF_UARTE=y

CONFIG_UART_1_NRF_FLOW_CONTROL=y

#CONFIG_BOARD_NRF9160DK_UART0_ARDUINO=y

#CONFIG_BOARD_NRF9160DK_UART0_VCOM=n

nrf9160dk_nrf9160ns.overlay:

/* Needed to get NRF_PWMn defined. */
&pwm1 {
	status = "okay";
};

&pwm2 {
	status = "okay";
};

&pwm3 {
	status = "okay";
};


&uart1 {
	current-speed = <9600>;
	status = "okay";
	tx-pin = <1>;
	rx-pin = <0>;
	rts-pin = <14>;
	cts-pin = <15>;
};

&uart0 {
	current-speed = <9600>;
	status = "ok";
	tx-pin = <10>;
	rx-pin = <11>;
	rts-pin = <12>;
	cts-pin = <13>;
};

The same is defined as an nrf9160dk_nrf9160.overlay file in the SPM folder.

When I try to build my application, I get a Kconfig error regarding the CONFIG_UART_1_NRF_UARTE=y. Could you help me understand what more could be required to change for it to work for UART_0.

Regards,

Adeel.

[Simon]

In NCS v1.3.0 the configurations CONFIG_UART_<x>_NRF_UARTE are not directly user-configurable and you can not set them in the prj.conf file. These configurations will get their value from the Device Tree. E.g. if you have enabled uart1 in the overlay file (status="okay"), the configuration UART_1_NRF_UARTE will get enabled here.

So in short, just removed CONFIG_UART_1_NRF_UARTE from prj.conf.

Another thing to be aware of is that UART1 will automatically get routed to VCOM2 due to this. In order to avoid this, flash the nRF9160dk_nrf52840 (on the nRF9160DK) with a hello world sample with this configuration:

BOARD_NRF9160DK_UART1_ARDUINO=y
BOARD_NRF9160DK_UART1_VCOM=n

Best regards,

Simon

[Adeel]

Hi Simon,

Okay. I understood the first part.

I try to flash the hello world example and I first switch the SW5 to nrf52. Then I add your configurations to the prj.conf file. But when I load the project, it again gives me KConfig errors here as well.

This is when I try to build the hello world sample to flash for nRF9160dk_nrf52840. Is there something I am missing again.

2287.board_controller_uart1.hex . I found this file from another post : https://devzone.nordicsemi.com/f/nordic-q-a/45476/connecting-uart1-to-a-periph-on-nrf9160-dk/178988#178988. Could I use this directly to flash the nRF9160dk_nrf52840 board ?

Regards,

Adeel.

[Adeel]

Hi Simon,

Thanks for the tip :). I was finally able to communicate through the RS-485 module. The problem was with the voltage mismatch. The nrf9160dk has a switch to change between 1.8 and 3V for the I/O. 

As a next step, I was trying to enable my receiver as well through my GPIO's. What is the normal voltage output that I can get through my GPIO ? 

Will the logic of enabling and disabling my RS-485 DE and RE be the same as in this example : https://devzone.nordicsemi.com/f/nordic-q-a/55059/nrf51822-with-modbus-ttl-to-rs485/223289#223289

Regards,

Adeel.

[Adeel]

Hi Simon,

Regarding the same, I had a query regarding the GPIO Pins.

I have now tied up my DE / RE to 1 pin (Pin 0.12) and configured that pin as an output (nrf_gpio_cfg_output(12)). So when I transmit, I keep this pin to High (nrf_gpio_pin_set(12)) and after my uart_fifo_fill(), I keep a certain delay and pull the pin low (nrf_gpio_pin_clear(12)) to enable the receive. 

nrf_gpio_cfg_output(12);

while(1){

        nrf_gpio_pin_set(12);
            
        uart_fifo_fill(uart, (uint8_t*)(mstatus.request.frame), mstatus.request.length);   
               

        k_sleep(K_SECONDS(2));

        nrf_gpio_pin_clear(12);
            }

However, I see that the GPIO pins dont work the way I need. As in, the pin does not change from transmit to receive. Is it due to the voltage mismatch ? 

I read the datsasheet of the MAX-485 device that I am using and it says it needs more than 2V. 

Does the GPIO pins normally output 1.8V or 3V in nrf9160DK ?

Regards,

Adeel.

[Simon]

If you set the VDD IO switch to 3V the GPIO will output 3V and if you set it to 1v8, it will output 1.8v. I tested this with a multimeter and P0.28, I've attached the sample below:

3124.toggle_gpio_regs.7z

However, according to Modbus (RS-485) Using Arduino, you should connect RE and DE to 5V in order to use the RS485 as a transmitter. The GPIOs only output 3v. I think you can solve this using a FET: https://devzone.nordicsemi.com/f/nordic-q-a/10542/5-volts-output-on-nrf51-dk-pin

Best regards,

Simon

[Adeel]

Hi Simon,

Thanks or the tip. Instead of that, I got the RS485 module to work with 3V and so I was able to transmit and receive from the module .

Thanks for the help. I finally got things running at my end.

Regards,

Adeel.

[Simon]

Nice! I'm happy you finally made it work

Best regards,

Simon