Lpuart example throws error

[viswa]

Hi Everyone,

I tried to build lpUart example from samples available. I was trying to debug then I got the breakpoint on 

"__ASSERT(lpuart, "Failed to get the device");"

I will add .conf files and the overlay I got from the example.

please let me know, what did i do wrong?

/********* nrf52840dk_nrf52840.conf file **********/
# Copyright (c) 2020 Nordic Semiconductor
#
# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
#

CONFIG_UART_1_ASYNC=y

CONFIG_UART_1_INTERRUPT_DRIVEN=y
CONFIG_UART_1_NRF_HW_ASYNC=y
CONFIG_UART_1_NRF_HW_ASYNC_TIMER=2
CONFIG_NRFX_TIMER2=y

/******** prj.conf **********/

CONFIG_NRF_SW_LPUART=y

CONFIG_USE_SEGGER_RTT=n
CONFIG_LOG=y
CONFIG_NO_OPTIMIZATIONS=y
CONFIG_ASSERT=y

# Comment this section for debugging
# CONFIG_CONSOLE=n
# CONFIG_UART_CONSOLE=n

# Uncomment to use lpuart using interrupt driven API
CONFIG_NRF_SW_LPUART_INT_DRIVEN=y

/**********.Overlay file **********/

&uart1 {
	rx-pin = <44>;
	tx-pin = <45>;
	/delete-property/ rts-pin;
	/delete-property/ cts-pin;

	lpuart: nrf-sw-lpuart {
		compatible = "nordic,nrf-sw-lpuart";
		status = "okay";
		label = "LPUART";
		req-pin = <46>;
		rdy-pin = <47>;
	};
};

// &uart0 {
// 	status = "disabled";
// };

&gpiote {
	interrupts = <6 NRF_DEFAULT_IRQ_PRIORITY>;
};

[Priyanka]

Hi,

Could you try un-commenting the lines 18,19 and 20 in the .overlay file?

Regards,

Priyanka

[viswa]

Somehow I'm able to build. Now I have enabled interrupt driven lpuart option.

CONFIG_NRF_SW_LPUART_INT_DRIVEN=y

I expect the code to work with only two lines, does it still need rdy & req pins as mentioned in .Overlay file?

&uart1 {
	rx-pin = <44>;
	tx-pin = <45>;
	/delete-property/ rts-pin;
	/delete-property/ cts-pin;

	lpuart: nrf-sw-lpuart {
		compatible = "nordic,nrf-sw-lpuart";
		status = "okay";
		label = "LPUART";
		req-pin = <46>;
		rdy-pin = <47>;
	};
};

[Priyanka]

You don't have to disable the req and rdy pins even if you are using interrupt driven UART. You can also use te lpuart driver when enabling the interrupt driven UART.

Regards,

Priyanka

[viswa]

So interrupt driven lpUart code should work with only tx and Rx lines then. But i couldn't see any data on terminal when I did that. I will get data only when i connect req and rdy lines.

Basically I want to use only two pins for uart, we have hw limitation where we can't spare any more pins for nordic chip.

Now... how to configure uart? and is there any example code with simple interrupt driven uart?

[Priyanka]

Though this seems right, it might result in an error. If you wish to disable the flow control pins, then it should be better to configure a normal UART and not LPUART since the main feature of LPUART is the usage of the flow control pins which allows in low power operation. You could try using the normal UART and then try disabling the hw-flow-control. 

Try referring to this sample by Simon where he modified the lpuart sample to use the normal UART driver and without flow control.

Regards,

Priyanka

[viswa]

Hi Priyanka

Thanks to you and @simon-iversen. I'm able to run it.