Hi,
In order to determine signal strength we parse the AT+CESQ response and regularly get +CESQ: 99,99,255,255,255,255 (the final number being the strength), but the connection and connectivity is perfectly fine. Is there a reason 255 is returned for the strength even though all connectivity is good?
Thanks!
In my MQTT project.
@ CDMA echo={ AT+CREG?...+CREG: 2,1,"27E8","01965335",7....OK... }
@ CDMA echo={ AT+CESQ...+CESQ: 99,99,255,255,20,64....OK... }
@ CDMA echo={ AT+CSQ...+CSQ: 31,4....OK... }
AT+CESQ the final bytes is not 255. it shoulde be (0-97,255)
<rsrp> Number Reference Signal Received Power (RSRP):
• 0: less than -140 dBm
• 1..96: from -140 dBm to -45 dBm with 1 dBm steps
• 97: -44 dBm or greater
• 255: not known or not detectable
I am not sure why your URC return is 255?
Maybe it depends on the CDMA/4G system services side.
Hi, GJSea!
Are you using Power Saving Mode(PSM) in your project? While the device is in PSM the radio is off and the device is disconnected.
I have not seen a similar behavior in any other cases, so I must reach out to the modem team if the above is not the case.
Best regards,
Carl Richard
Hi Carl,
Ahh you're right, the device was in a PSM state, and I'd say 2 out of 10 times we get 'unknown'. Our intent is to send the signal strength over MQTT, but if PSM isn't exited until the modem is awoken when sending the MQTT payload then there is a good chance of receiving unknown. Is the only workaround to send a dummy HTTP request at the beginning of our wake cycle, then poll the signal strength, then upload our main payload?
Thanks!
Hi again!
Glad we figured that out! It's unfortunately a sort of "chicken and egg" scenario as you must be out of PSM before RSRP can be fetched. A dummy HTTP request should be an ok workaround, but any transmission from the modem will trigger a wakeup so from a power consumption perspective a dummy UDP message could be cheaper.
Best regards,
Carl Richard
Now, I also encountered this problem, when I started my project, I used the AT command to query CESQ, it returned was 255. However, when i call the sample code for MQTT and find that it can connect to an LTE network, and even more bizarrely, on my other PCBA board, I write the same firmware and CESQ returns the correct values, which is very strange!
I confirm that I did not control the modem to enter PSM mode. This is my prj.conf file:
#
# Copyright (c) 2019 Nordic Semiconductor ASA
#
# SPDX-License-Identifier: LicenseRef-BSD-5-Clause-Nordic
#
# General config
CONFIG_NEWLIB_LIBC=y
CONFIG_NEWLIB_LIBC_FLOAT_PRINTF=y
CONFIG_ASSERT=y
CONFIG_REBOOT=y
CONFIG_GPIO=y
CONFIG_TRUSTED_EXECUTION_NONSECURE=y
# Log
CONFIG_LOG=y
CONFIG_LOG_IMMEDIATE=y
CONFIG_USE_SEGGER_RTT=y
CONFIG_LOG_BACKEND_RTT=y
CONFIG_LOG_BACKEND_UART=n
CONFIG_LOG_DEFAULT_LEVEL=4
CONFIG_LOG_MODE_OVERFLOW=y
CONFIG_LOG_BACKEND_RTT_MODE_DROP=y
CONFIG_LOG_BACKEND_SHOW_COLOR=n
CONFIG_LOG_BACKEND_FORMAT_TIMESTAMP=n
# Modem info
CONFIG_MODEM_INFO=y
# BSD library
CONFIG_BSD_LIBRARY=y
CONFIG_BSD_LIBRARY_TRACE_ENABLED=n
# Flash
CONFIG_FLASH=y
CONFIG_IMG_ERASE_PROGRESSIVELY=y
# NVS
CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_NVS=y
CONFIG_NVS_LOG_LEVEL_DBG=y
CONFIG_MPU_ALLOW_FLASH_WRITE=y
# GPS
CONFIG_AT_CMD=y
CONFIG_AT_NOTIF=y
# AT_CMD
CONFIG_AT_HOST_LIBRARY=y
CONFIG_UART_INTERRUPT_DRIVEN=y
# Console
CONFIG_CONSOLE_SUBSYS=n
CONFIG_CONSOLE_HANDLER=n
CONFIG_CONSOLE_GETCHAR=n
CONFIG_CONSOLE=n
CONFIG_RTT_CONSOLE=n
CONFIG_UART_CONSOLE=n
# Enable SUPL client support AGPS
CONFIG_SUPL_CLIENT_LIB=n
# Network
CONFIG_NETWORKING=y
CONFIG_NET_NATIVE=n
CONFIG_NET_SOCKETS=y
CONFIG_NET_SOCKETS_OFFLOAD=y
CONFIG_NET_SOCKETS_POSIX_NAMES=y
CONFIG_NET_SOCKETS_SOCKOPT_TLS=y
# LTE link control
CONFIG_LTE_LINK_CONTROL=y
CONFIG_LTE_AUTO_INIT_AND_CONNECT=n
#add by liming
#CONFIG_POWER_OPTIMIZATION_ENABLE=n
CONFIG_LTE_NETWORK_MODE_LTE_M_GPS=n
#CONFIG_LTE_LINK_CONTROL_LOG_LEVEL_DBG=y
CONFIG_LTE_NETWORK_MODE_NBIOT_GPS=y
CONFIG_LTE_LEGACY_PCO_MODE=y
#CONFIG_LTE_PSM_REQ_RPTAU="00000110"
#CONFIG_LTE_PSM_REQ_RAT="00000010"
# MQTT
CONFIG_MQTT_LIB=y
CONFIG_MQTT_LIB_TLS=y
#add by liming
CONFIG_MQTT_CLIENT_ID="devzone_client"
CONFIG_MQTT_BROKER_HOSTNAME="test.mosquitto.org"
CONFIG_MQTT_BROKER_PORT=8884
CONFIG_SEC_TAG=51966
CONFIG_PEER_VERIFY=1
# Appliaction
#CONFIG_MQTT_PUB_TOPIC="/my/publish/topic"
#CONFIG_MQTT_SUB_TOPIC="/my/subscribe/topic"
#CONFIG_MQTT_CLIENT_ID="my-client-id"
#CONFIG_MQTT_BROKER_HOSTNAME="mqtt.eclipse.org"
#CONFIG_MQTT_BROKER_PORT=1883
# Library for buttons and LEDs
CONFIG_DK_LIBRARY=y
CONFIG_DK_LIBRARY_INVERT_LEDS=n
# Heap and stacks
CONFIG_HEAP_MEM_POOL_SIZE=16384
CONFIG_MAIN_STACK_SIZE=8192
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048
CONFIG_HW_STACK_PROTECTION=y
# MCUBOOT
CONFIG_BOOTLOADER_MCUBOOT=y
CONFIG_IMG_MANAGER=y
CONFIG_MCUBOOT_IMG_MANAGER=y
# SPI
CONFIG_SPI=y
CONFIG_SPI_NRFX=y
CONFIG_SPI_2=y
CONFIG_SPI_2_NRF_SPIM=y
CONFIG_SPI_3=y
CONFIG_SPI_3_NRF_SPIM=y
# I2C
CONFIG_I2C=y
CONFIG_I2C_NRFX=y
CONFIG_I2C_1=y
CONFIG_I2C_1_NRF_TWIM=y
CONFIG_I2C_2=n
CONFIG_I2C_2_NRF_TWIM=n
CONFIG_I2C_INIT_PRIORITY=60
# UART
CONFIG_SERIAL=y
CONFIG_UART_INTERRUPT_DRIVEN=y
#CONFIG_UART_LINE_CTRL=y
#CONFIG_UART_0_NRF_UART=y
#CONFIG_UART_0_NRF_UARTE=y
#CONFIG_UART_0_NRF_FLOW_CONTROL=n
#CONFIG_UART_1_NRF_UARTE=n
#CONFIG_UART_1_NRF_FLOW_CONTROL=n
# Use smaller buffers for net_buf as CANBUS packets are quite small.
CONFIG_NET_BUF_DATA_SIZE=64
CONFIG_NET_BUF_USER_DATA_SIZE=1
# Main thread
CONFIG_MAIN_STACK_SIZE=8192
CONFIG_HEAP_MEM_POOL_SIZE=4096
