nRF9161 nRF52840 lp_uart communication

[Guillaume59]

Hello

I have a problem setting up communication between a nRF9161 and a nRF52840.

I have a custom board with a nRf9161 and a nRF52840. These two are connected with 5 lines.

nRF9161	------	nRF52840
P0.21	---	P0.29
P0.23	---	P0.28
P0.24	---	P0.02
P0.26	---	P0.13
P0.22	---	nRESET

I am using the lp_uart sample with my custom board files on the nrf52840.

Is it necessary to set the nrf52840 reset line in the custom board files? If so, please explain wy.

When i try to use the bluetooth from the nrf9161 I get this response in my logs :

*** Booting nRF Connect SDK v3.5.99-ncs1 ***:
[00:00:00.264,862] <inf> ED2_Gateway_fw: Starting ED2-Gateway-fw
[00:00:00.264,892] <inf> ED2_Gateway_fw: BLE start
[00:00:01.275,177] <wrn> lpuart: Tx timeout
ASSERTION FAIL [err == 0] @ WEST_TOPDIR/zephyr/subsys/bluetooth/host/hci_core.c:331
        command opcode 0x0c03 timeout with err -11
[00:00:10.275,421] <err> os: r0/a1:  0x00000003  r1/a2:  0x00000000  r2/a3:  0x00000002
[00:00:10.275,421] <err> os: r3/a4:  0x2000cce0 r12/ip:  0x00000010 r14/lr:  0x0000ea45
[00:00:10.275,451] <err> os:  xpsr:  0x41000000
[00:00:10.275,451] <err> os: Faulting instruction address (r15/pc): 0x0000ea50
[00:00:10.275,482] <err> os: >>> ZEPHYR FATAL ERROR 3: Kernel oops on CPU 0
[00:00:10.275,512] <err> os: Current thread: 0x2000d660 (unknown)
[00:00:10.499,938] <err> fatal_error: Resetting system

I have to mention that the connection works SOMETIMES, but most of the time i get this error and the board restarts.

Could you help me with my issue please?

Thank you.

[Einar Thorsrud]

Hi,

I am glad to hear you got it working. LP UART use signals to indicate that there is data ready to be sent, so that the receiver can wake up on it (using pin interrupt), in order to achieve low power. Could there be a problem with the pins or traces you use for the LP UART signals?

If current consumption is not an imporatnt factor for your device, LP UART will not give you eny benefints compared to using only normal UART.