Simple MQTT sample for nrf9160

[Joao Filipe]

Hi everyone

I'm trying to implement the MQTT sample on my devkit but I'm a little bit lost. I never used the MQTT before, so its a little bit of a chocking to me.

From what I know, a broker is an element responsible for manage the publish and subscriptions of  mqtt protocol. We need a client and a server and publish/subscribe to topics for the communication happens. Is that alright?

So, I wanted to know if you can guide me.

I followed the instructions here "https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/nrf9160/mqtt_simple/README.html". But I were confused when configuring the mqtt broker.

I installed the Mosquitto for windows https://mosquitto.org/download/.

And checking https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.iotsdk.v0.9.0%2Fiot_sdk_user_guides_mosquitto.html I tried to configure the broker but I was completely lost. 

Like I said, I never used this or something close before and If you could guide me how to get this example working it would be great.

Sorry If this post is not so useful.

Have a nice day

[Didrik Rokhaug]

Hi.

 

From what I know, a broker is an element responsible for manage the publish and subscriptions of  mqtt protocol. We need a client and a server and publish/subscribe to topics for the communication happens. Is that alright?

 Yes, this is correct. In MQTT there is no direct communication between two "devices" (including applications running on servers and similar), but instead everything goes via a Broker. It is kind of similar to you subscribing to a magazine, which is sent to you by the post office, not the magazine itself.

 

And checking https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.iotsdk.v0.9.0%2Fiot_sdk_user_guides_mosquitto.html

 This documentation is for the "IoT SDK", which is now a part of the nRF5 SDK. For the nRF9160, you should stick to the nRF Connect SDK, which is our only SDK with support for the nRF9160.

There are several public MQTT brokers available, and the mqtt_simple sample uses one of those, so you do not need to set up your own broker to test the sample.

What version of NCS do you use (are you on the master branch, or using one of the tags)?

If you use version 1.0.0, you need to change the hostname of the broker to "mqtt.eclipse.org". In later tags, this has already been done.

You can then use an MQTT client (I recommend MQTT.fx) to publish to "/my/subscripe/topic" and subscribe to "/my/publish/topic". What you publish to "/my/subscribe/topic" will be published by the nRF91 to "/my/publish/topic".

If you have further questions, feel free to as them!

Best regards,

Didrik

[Joao Filipe]

Hi. Thanks for fast reply.

My NCS tag version is 1.0.0. 

So I changed the hostname(from "iot.eclipse.org" to "mqtt.eclipse.org" at Kconfig, proj.conf and prj_qemu_x86. I dont know if it was to change in all 3 programs, but I changed in all.

Now, after I flash the MQTT sample to nrf9160 devkit, it says I got a connection.

OUTPUT:

The MQTT simple sample started

LTE Link Connecting ...

LTE Link Connected!

IPv4 Address found 137.135.83.217

[mqtt_evt_handler:166] MQTT client connected!

Subscribing to: my/subscribe/topic len 18

[mqtt_evt_handler:216] SUBACK packet id: 1234

After that I installed MQTT.fx. 

When I open it I have two options: 

->Local Mosquitto;

->M2M eclipse;

Which one should I select? And in any of that two options at "Edit connection Profiles" there's a Broker Address, different from one option to another. At local mosquitto is an ip, and at M2M eclipse is a link. Should I update the correct option to "mqtt.eclipse.org"??

So, until I get a response to this reply, and not knowing if I'm doing it right I choose M2M ecplise but altered the broker from "m2m.eclipse.org" to "mqtt.ecplise.org". Correct me if I'm wrong.

I pressed Connect and it connected, at least it says there.

And now what should I do to see interaction with the devkit?

Sorry if I didn't get there yet.

[Didrik Rokhaug]

MQTT.fx lets you store different brokers. To add a new one, you can press the "+" button at the bottom right of the window in your second screenshot, or you can modify one of the existing ones (as you did). In the second screenshot, you can also change settings such as keep-alive time and TLS.

In the "Publish" (see screenshot), you can publish to a topic by writing your message in the big text box that fills most of the window, and the topic in the small text box I have marked (you can also select topics you have previously published to from the drop-down menu). Also, remember that anyone can see what you are publishing to a public broker, so be careful not to share privet/sensitive information.

You can also change to the "Subscribe" view, where you can subscribe to a topic in a similar way. You can also scan for topics, but the public brokers tend to have too many topics for you to find the one you are looking for.

[Joao Filipe]

I think I'm getting there. So after devkit gets connection to broker, at Link Monitor it says 

Subscribing to: my/subscribe/topic len 18

If I publish and subscribe to that specific topic from MQTT.fx shouldn't I see that messages at link monitor?

Like it says here at point 3/4?? Because I'm not getting anything there.

[Didrik Rokhaug]

From MQTT.fx you should publish to "my/subscribe/topic", and subscribe to "my/publish/topic". You should then see the message you published to "my/subscribe/topic" echoed on "my/publish/topic"

(When testing right now, I had some trouble connecting to mqtt.eclipse.org (a disadvantage of using public brokers is that they are not always available), if you have similar problems, you could also try test.mosquitto.org)

The log should look something like this:

Fullscreen mqtt_simple.txt Download

***** Booting Zephyr OS v1.14.99-ncs2 *****
Flash region		Domain		Permissions
00 0x00000 0x08000 	Secure		rwxl
01 0x08000 0x10000 	Non-Secure	rwxl
02 0x10000 0x18000 	Non-Secure	rwxl
03 0x18000 0x20000 	Non-Secure	rwxl
04 0x20000 0x28000 	Non-Secure	rwxl
05 0x28000 0x30000 	Non-Secure	rwxl
06 0x30000 0x38000 	Non-Secure	rwxl
07 0x38000 0x40000 	Non-Secure	rwxl
08 0x40000 0x48000 	Non-Secure	rwxl
09 0x48000 0x50000 	Non-Secure	rwxl
10 0x50000 0x58000 	Non-Secure	rwxl
11 0x58000 0x60000 	Non-Secure	rwxl
12 0x60000 0x68000 	Non-Secure	rwxl
13 0x68000 0x70000 	Non-Secure	rwxl
14 0x70000 0x78000 	Non-Secure	rwxl
15 0x78000 0x80000 	Non-Secure	rwxl
16 0x80000 0x88000 	Non-Secure	rwxl
17 0x88000 0x90000 	Non-Secure	rwxl
18 0x90000 0x98000 	Non-Secure	rwxl
19 0x98000 0xa0000 	Non-Secure	rwxl
20 0xa0000 0xa8000 	Non-Secure	rwxl
21 0xa8000 0xb0000 	Non-Secure	rwxl
22 0xb0000 0xb8000 	Non-Secure	rwxl
23 0xb8000 0xc0000 	Non-Secure	rwxl
24 0xc0000 0xc8000 	Non-Secure	rwxl
25 0xc8000 0xd0000 	Non-Secure	rwxl
26 0xd0000 0xd8000 	Non-Secure	rwxl
27 0xd8000 0xe0000 	Non-Secure	rwxl
28 0xe0000 0xe8000 	Non-Secure	rwxl
29 0xe8000 0xf0000 	Non-Secure	rwxl
30 0xf0000 0xf8000 	Non-Secure	rwxl
31 0xf8000 0x100000 	Non-Secure	rwxl
Non-secure callable region 0 placed in flash region 0 with size 32.


SRAM region		Domain		Permissions
00 0x00000 0x02000	Secure		rwxl
01 0x02000 0x04000	Secure		rwxl
02 0x04000 0x06000	Secure		rwxl
03 0x06000 0x08000	Secure		rwxl
04 0x08000 0x0a000	Secure		rwxl
05 0x0a000 0x0c000	Secure		rwxl
06 0x0c000 0x0e000	Secure		rwxl
07 0x0e000 0x10000	Secure		rwxl
08 0x10000 0x12000	Non-Secure	rwxl
09 0x12000 0x14000	Non-Secure	rwxl
10 0x14000 0x16000	Non-Secure	rwxl
11 0x16000 0x18000	Non-Secure	rwxl
12 0x18000 0x1a000	Non-Secure	rwxl
13 0x1a000 0x1c000	Non-Secure	rwxl
14 0x1c000 0x1e000	Non-Secure	rwxl
15 0x1e000 0x20000	Non-Secure	rwxl
16 0x20000 0x22000	Non-Secure	rwxl
17 0x22000 0x24000	Non-Secure	rwxl
18 0x24000 0x26000	Non-Secure	rwxl
19 0x26000 0x28000	Non-Secure	rwxl
20 0x28000 0x2a000	Non-Secure	rwxl
21 0x2a000 0x2c000	Non-Secure	rwxl
22 0x2c000 0x2e000	Non-Secure	rwxl
23 0x2e000 0x30000	Non-Secure	rwxl
24 0x30000 0x32000	Non-Secure	rwxl
25 0x32000 0x34000	Non-Secure	rwxl
26 0x34000 0x36000	Non-Secure	rwxl
27 0x36000 0x38000	Non-Secure	rwxl
28 0x38000 0x3a000	Non-Secure	rwxl
29 0x3a000 0x3c000	Non-Secure	rwxl
30 0x3c000 0x3e000	Non-Secure	rwxl
31 0x3e000 0x40000	Non-Secure	rwxl

Peripheral		Domain		Status
00 NRF_P0		Non-Secure	OK
01 NRF_CLOCK		Non-Secure	OK
02 NRF_RTC1		Non-Secure	OK
03 NRF_NVMC		Non-Secure	OK
04 NRF_UARTE1		Non-Secure	OK
05 NRF_UARTE2		Secure		SKIP
06 NRF_TWIM2		Non-Secure	OK
07 NRF_SPIM3		Non-Secure	OK
08 NRF_TIMER0		Non-Secure	OK
09 NRF_TIMER1		Non-Secure	OK
10 NRF_TIMER2		Non-Secure	OK
11 NRF_SAADC		Non-Secure	OK
12 NRF_PWM0		Non-Secure	OK
13 NRF_PWM1		Non-Secure	OK
14 NRF_PWM2		Non-Secure	OK
15 NRF_PWM3		Non-Secure	OK
16 NRF_IPC		Non-Secure	OK
17 NRF_VMC		Non-Secure	OK
18 NRF_FPU		Non-Secure	OK
19 NRF_EGU1		Non-Secure	OK
20 NRF_EGU2		Non-Secure	OK
21 NRF_GPIOTE1		Non-Secure	OK

SPM: NS image at 0xc000
SPM: NS MSP at 0x20024558
SPM: NS reset vector at 0xe2c5
SPM: prepare to jump to Non-Secure image.
***** Booting Zephyr OS v1.14.99-ncs2 *****
The MQTT simple sample started
LTE Link Connecting ...
LTE Link Connected!
IPv4 Address found 5.196.95.208
[mqtt_evt_handler:166] MQTT client connected!
Subscribing to: my/subscribe/topic len 18
[mqtt_evt_handler:216] SUBACK packet id: 1234
[mqtt_evt_handler:181] MQTT PUBLISH result=0 len=5
Received: Hello
Publishing: Hello
to topic: my/publish/topic len: 16
[mqtt_evt_handler:206] PUBACK packet id: 48663

[Joao Filipe]

It worked pretty well. I was already trying that but I was not publishing and subscribing to the right place. So thank you so much about that. One last question. Is it possible to measure the power consumption of MQTT sample? And if so, how is that possible? Is just flash MQTT sample at the devkit, and follow instructions like it says here https://devzone.nordicsemi.com/nordic/cellular-iot-guides/b/hardware-design/posts/measuring-psm-idle-current-on-the-nrf91-dk?

[Didrik Rokhaug]

Yes, by following that guide, you should be able to get a power consumption measurement.