nRF9160: Simple MQTT¶
The Simple MQTT sample demonstrates how to easily connect an nRF9160 SiP to an MQTT broker and send and receive data.
The sample supports the following development kit:
Additionally, the sample supports X86 Emulation (QEMU).
The sample is configured to compile and run as a non-secure application on nRF91’s Cortex-M33. Therefore, it automatically includes the Secure Partition Manager that prepares the required peripherals to be available for the application.
You can also configure it to use TF-M instead of Secure Partition Manager.
The sample connects to an MQTT broker and publishes the data it receives on the configured subscribe topic to the configured publish topic. On a button press event, the sample publishes the configured message to the configured publish topic. By default, the sample can establish a secure (TLS) connection or a non-secure connection to the configured MQTT broker. The sample disables power saving modes (PSM and eDRX) so that network events are processed as soon as possible.
See Configuring your application for information about how to permanently or temporarily change the configuration.
Check and configure the following configuration options for the sample:
- MQTT Broker host name¶
This configuration option defines the MQTT Broker host name.
- MQTT Client ID¶
This configuration option specifies the MQTT Client ID.
- MQTT Subscribe topic¶
This configuration option sets the MQTT Subscribe topic.
- MQTT Publish topic¶
This configuration option sets the MQTT Publish topic.
- MQTT Broker Port¶
This configuration option specifies the port number associated with the MQTT broker.
- Button event publish message¶
This configuration option specifies the message text which is published on a button press.
- Button number for publish¶
This configuration option specifies the button number which, when pressed, will publish an MQTT message.
- MQTT broker reconnect delay¶
This configuration option specifies the delay (in seconds) before attempting to reconnect to the broker.
- LTE connection retry delay¶
This configuration option specifies delay (in seconds) before attempting to retry LTE connection.
The sample provides the following predefined configuration files for the following development kits:
prj.conf- For nRF9160 DK
prj_qemu_x86.conf- For x86 Emulation (QEMU)
In addition, the sample provides overlay configuration files, which are used to enable additional features in the sample:
overlay-tls.conf- TLS overlay configuration file for nRF9160 DK
overlay-qemu-x86-tls.conf- TLS overlay configuration file for x86 Emulation (QEMU)
overlay-carrier.conf- LWM2M carrier support for nRF9160 DK
They are located in
To add a specific overlay configuration file to the build, add the
-- -DOVERLAY_CONFIG=<overlay_config_file> parameter to the
west build command.
The following command builds the sample with the TLS configuration for nRF9160 DK:
west build -b nrf9160dk_nrf9160ns -- -DOVERLAY_CONFIG=overlay-tls.conf
The CA certificate for the default MQTT broker is included in the project and automatically provisioned after boot if the sample is built with the TLS configuration.
This sample can be found under
samples/nrf9160/mqtt_simple in the nRF Connect SDK folder structure.
The sample is built as a non-secure firmware image for the nrf9160dk_nrf9160ns build target. Because of this, it automatically includes the Secure Partition Manager. You can also configure it to use TF-M instead of SPM.
See Building and programming a sample application for information about how to build and program the application.
After programming the sample to your development kit, test it by performing the following steps:
Connect the kit to the computer using a USB cable. The kit is assigned a COM port (Windows) or ttyACM device (Linux), which is visible in the Device Manager.
Connect to the kit with a terminal emulator (for example, PuTTY). See How to connect with PuTTY for the required settings.
Reset your nRF9160 DK.
Observe that the sample displays the following information in the terminal:
The MQTT simple sample started
Observe that the development kit connects to the configured MQTT broker (
CONFIG_MQTT_BROKER_HOSTNAME) after it gets the LTE connection. At this stage, the development kit is ready to echo the data sent to it on the configured subscribe topic (
Use an MQTT client like Mosquitto to subscribe to and publish data to the broker. Observe that the development kit publishes all the data that you publish to
The following serial UART output is displayed in the terminal emulator:
*** Booting Zephyr OS build v2.4.0-ncs1-rc1-6-g45f2d5cf8ea4 *** <inf> mqtt_simple: The MQTT simple sample started <inf> mqtt_simple: LTE Link Connecting... <inf> mqtt_simple: LTE Link Connected! <inf> mqtt_simple: Disabling PSM and eDRX <inf> mqtt_simple: IPv4 Address found 220.127.116.11 <inf> mqtt_simple: MQTT client connected <inf> mqtt_simple: Subscribing to: my/subscribe/topic len 18 <inf> mqtt_simple: SUBACK packet id: 1234 <inf> mqtt_simple: Publishing: Hello from nRF91 MQTT Simple Sample <inf> mqtt_simple: to topic: my/publish/topic len: 16 <inf> mqtt_simple: PUBACK packet id: 51700
Public MQTT brokers might be unstable.
If you experience problems connecting to the MQTT broker, try switching to another MQTT broker by changing the value of the
CONFIG_MQTT_BROKER_HOSTNAME configuration option.
CONFIG_MQTT_BROKER_HOSTNAME configuration option is changed and the overlay TLS configuration is used, the included CA certificate must be updated with the CA certificate for
the newly configurated MQTT broker.