Kernel panic when overlaying UART TX and RX pins on nrf52833_nrf52820

Question

When I do an overlay like this:

&pinctrl {
uart0_default: uart0_default {
		group1 {
			psels = <NRF_PSEL(UART_TX, 0, 31)>,
				<NRF_PSEL(UART_RX, 0, 30)>;
		};
	};

};

I get kernel panic:

[00:00:00.000,000] <err> os: ARCH_EXCEPT with reason 4

[00:00:00.000,000] <err> os: r0/a1:  0x00000004  r1/a2:  0x00000070  r2/a3:  0x00000009
[00:00:00.000,000] <err> os: r3/a4:  0x00000000 r12/ip:  0x00000010 r14/lr:  0x00003535
[00:00:00.000,000] <err> os:  xpsr:  0x6100000b
[00:00:00.000,000] <err> os: Faulting instruction address (r15/pc): 0x00008632
[00:00:00.000,000] <err> os: >>> ZEPHYR FATAL ERROR 4: Kernel panic on CPU 0
[00:00:00.000,000] <err> os: Fault during interrupt handling

[00:00:00.000,000] <err> os: Current thread: 0x200021b0 (unknown)
[00:00:00.000,000] <err> fatal_error: Resetting system

If I set the overlay back to 6 & 8 it works.

If I set TX/RX to pin 11/13, I get 11/8.

Are there some restrictions here that I am not aware of?

Rgds Tage

Sigurd · Accepted Answer

Hi, 
 Tage Korsdal Nielsen said: TX accepts both 3 and 4, but RX is stuck at PIN 8. 
 Look at this file, https://github.com/nrfconnect/sdk-zephyr/blob/v3.3.99-ncs1/boards/arm/nrf52833dk_nrf52820/nrf52833dk_nrf52820-pinctrl.dtsi#L6 , RX seem to be set in group2

Kernel panic when overlaying UART TX and RX pins on nrf52833_nrf52820

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