nRF9160, the response to any "CFUN" command is always ERROR.

[Stas Jis]

We use nRF9160 on our own board.
The firmware "Serial lte modem" is installed on the chip with connection to an external MCU.

#\nUse\nUART_0\n(when\nworking\nwith\nPC\nterminal)
#CONFIG_UART_0_NRF_HW_ASYNC_TIMER=2
#\nUse\nUART_2\n(when\nworking\nwith\nexternal\nMCU)
CONFIG_SLM_CONNECT_UART_2=y
CONFIG_UART_2_NRF_HW_ASYNC_TIMER=2

A port is connected to the board to communicate with the nRF9160 via the terminal. The nRF9160 responds to "AT" or "AT%XSYSTEMMODE=1,0,0,0" commands (response is always "OK"), but any attempts to execute commands like:
- AT+CFUN=0;
- AT+CFUN=1;
- AT+CFUN?;
- AT+CFUN=?
Always returns an "ERROR" response (with a delay of a few seconds). What could be the reason?

[Charlie]

Hi Stas,

Set CONFIG_SLM_LOG_LEVEL_DBG=y and observe log from Jlink RTT viewer should be able to see the UART RX content.

Can you try this method to debug your issue?  nRF9160DK+ LInk monitor can be used as a comparation.

Best regards,

Charlie

[Stas Jis]

Charlie, 
I am attaching the log from J Link RTT Viewer:

00> [00:00:00.156,127] <inf> slm: Serial LTE Modem
00> [00:00:00.182,464] <dbg> slm_at_host: TX
00>                                       52 65 61 64 79 0d 0a                             |Ready..          
00> [00:00:00.182,495] <dbg> slm_fota.slm_fota_post_process: FOTA result 0,0,0
00> [00:00:00.185,882] <inf> slm_at_host: at_host init done
00> [00:00:43.211,883] <dbg> slm_at_host: RX
00>                                       41 54                                            |AT               
00> [00:00:43.219,299] <dbg> slm_at_host: TX
00>                                       0d 0a                                            |..               
00> [00:00:43.219,329] <dbg> slm_at_host: TX
00>                                       4f 4b 0d 0a                                      |OK..             
00> [00:00:46.803,833] <dbg> slm_at_host: RX
00>                                       41 54 2b 43 46 55 4e 3d  30                      |AT+CFUN= 0       
00> [00:00:46.804,351] <dbg> slm_at_host.uart_callback: RX_DISABLED
00> [00:00:46.810,699] <err> slm_at_host: AT command error, type: 1
00> [00:00:46.810,729] <dbg> slm_at_host: TX
00>                                       0d 0a                                            |..               
00> [00:00:46.810,760] <dbg> slm_at_host: TX
00>                                       45 52 52 4f 52 0d 0a                             |ERROR..          
00> [00:01:01.644,348] <dbg> slm_at_host: RX
00>                                       41 54 2b 43 46 55 4e 3d  30                      |AT+CFUN= 0       
00> [00:01:01.644,836] <dbg> slm_at_host.uart_callback: RX_DISABLED
00> [00:01:01.651,214] <err> slm_at_host: AT command error, type: 1
00> [00:01:01.651,245] <dbg> slm_at_host: TX
00>                                       0d 0a                                            |..               
00> [00:01:01.651,275] <dbg> slm_at_host: TX
00>                                       45 52 52 4f 52 0d 0a                             |ERROR..          
00> [00:01:08.068,695] <dbg> slm_at_host: RX
00>                                       41 54 2b 43 46 55 4e 3f                          |AT+CFUN?         
00> [00:01:08.069,183] <dbg> slm_at_host.uart_callback: RX_DISABLED
00> [00:01:08.075,531] <err> slm_at_host: AT command error, type: 1
00> [00:01:08.075,561] <dbg> slm_at_host: TX
00>                                       0d 0a                                            |..               
00> [00:01:08.075,592] <dbg> slm_at_host: TX
00>                                       45 52 52 4f 52 0d 0a                             |ERROR..

Just in case, here's the config:

#
#\nCopyright\n(c)\n2020\nNordic\nSemiconductor\nASA
#
#\nSPDX-License-Identifier:\nLicenseRef-Nordic-5-Clause
#
#\nGeneral\nconfig
CONFIG_LOG=y
CONFIG_LOG_DEFAULT_LEVEL=3
CONFIG_STACK_SENTINEL=y
CONFIG_NEWLIB_LIBC=y
CONFIG_NEWLIB_LIBC_FLOAT_PRINTF=y
CONFIG_RING_BUFFER=y

#\nSegger\nRTT
CONFIG_USE_SEGGER_RTT=y
CONFIG_RTT_CONSOLE=y
CONFIG_UART_CONSOLE=n
CONFIG_LOG_BACKEND_RTT=y
CONFIG_LOG_BACKEND_UART=n

#\nNetwork
CONFIG_NETWORKING=y
CONFIG_NET_SOCKETS=y
CONFIG_NET_NATIVE=n

#\nModem\nlibrary
CONFIG_NRF_MODEM_LIB=y
#\nAlign\nthe\nmax\nFD\nentry\nto\nNRF_MODEM_MAX_SOCKET_COUNT(8)
CONFIG_POSIX_MAX_FDS=8
#\nEnable\nbelow\nfor\nmodem\ntrace
CONFIG_NRF_MODEM_LIB_TRACE_ENABLED=y

#\nUse\nGPIO
CONFIG_GPIO=y
CONFIG_GPIO_NRFX=y
CONFIG_GPIO_NRF_P0=y

#\nUART\ninterface
CONFIG_SERIAL=y
CONFIG_UART_ASYNC_API=y
CONFIG_NRFX_TIMER2=y

#\nStacks\nand\nheaps
CONFIG_MAIN_STACK_SIZE=4096
CONFIG_HEAP_MEM_POOL_SIZE=16384
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=4096

#\nDevice\npower\nmanagement
CONFIG_PM_DEVICE=y

#\nFOTA
CONFIG_HTTP_PARSER_URL=y
CONFIG_FOTA_DOWNLOAD=y
CONFIG_FOTA_DOWNLOAD_PROGRESS_EVT=y
CONFIG_DFU_TARGET=y
CONFIG_DOWNLOAD_CLIENT=y
CONFIG_DOWNLOAD_CLIENT_STACK_SIZE=4096
CONFIG_BOOTLOADER_MCUBOOT=y
CONFIG_IMG_MANAGER=y

#\nFLASH
CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_FLASH_MAP=y
CONFIG_MPU_ALLOW_FLASH_WRITE=y
CONFIG_IMG_ERASE_PROGRESSIVELY=y

#\nSettings
CONFIG_SETTINGS=y
CONFIG_SETTINGS_FCB=y
CONFIG_FCB=y

#\nnRF\nCloud
CONFIG_CLOUD_API=y
CONFIG_NRF_CLOUD_MQTT=y
CONFIG_NRF_CLOUD_FOTA=n
CONFIG_NRF_CLOUD_AGPS=y
CONFIG_NRF_CLOUD_PGPS=y
CONFIG_NRF_CLOUD_CELL_POS=y
CONFIG_NRF_CLOUD_LOG_LEVEL_INF=y
CONFIG_DATE_TIME=y
CONFIG_MODEM_INFO=y
CONFIG_MODEM_INFO_ADD_DATE_TIME=n
CONFIG_AT_MONITOR=y
CONFIG_MODEM_JWT=y
#\nUse\n"nrf-<IMEI>"\nas\nthe\ndefault\ndevice_id\nformat
#\nUse\n"<device_uuid>"\nas\nthe\ndevice_id\nformat\nby\nbelow
#CONFIG_NRF_CLOUD_CLIENT_ID_SRC_INTERNAL_UUID=y

#
#\nSLM-specific\nconfigurations
#
CONFIG_SLM_CUSTOMIZED=n
CONFIG_SLM_LOG_LEVEL_INF=y
CONFIG_SLM_EXTERNAL_XTAL=n
CONFIG_SLM_START_SLEEP=n
#\nUse\nUART_0\n(when\nworking\nwith\nPC\nterminal)
#CONFIG_UART_0_NRF_HW_ASYNC_TIMER=2
#\nUse\nUART_2\n(when\nworking\nwith\nexternal\nMCU)
CONFIG_SLM_CONNECT_UART_2=y
CONFIG_UART_2_NRF_HW_ASYNC_TIMER=2
#\nnRF\nCloud\nbased\nlocation\nservices
CONFIG_SLM_AGPS=y
CONFIG_SLM_PGPS=y
CONFIG_SLM_CELL_POS=y
CONFIG_SLM_LOG_LEVEL_DBG=y

Charlie, settings from dts files, can help?

[Charlie]

Hi Stas,

There is one former case very close to your issue, can you try the solution mentioned on https://devzone.nordicsemi.com/f/nordic-q-a/82885/most-at-commands-return-error/344237#344237

Best regards,

Charlie

[Stas Jis]

Charlie,
The problem was in the nRF9160 firmware version.
Everything is working now, thanks for the help.