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How to do MQTT on EXS82 platform

Tutorial, December 27, 2019 - 3:39am, 8422 views

M2M

Because EXS82 doesn’t support JAVA like PLS62 and ELS61 series, we need to use AT command to achieve MQTT feature.

Environment setting:

Ubuntu 18.04.03 for MQTT broker and client
EXS82 CS2 FW:REVISION 00.038, A-REVISION 01.000.00

Steps:

Ubuntu:

1. Install MQTT related update and

"sudo apt install -y mosquito" (Install Mosquitto MQTT Broker)

"sudo apt install -y mosquitto-clients" (Install Mosquitto Client)

2. Make sure MQTT subscriber/publisher works

mosquitto_sub -h IP -t Topic (Create a subscriber for specific Topic)

ex: "mosquitto_sub -h 60.250.82.33 -t test" means to wait for Topic as test message

mosquitto_pub -h IP -t Topic -m Message (Create a publisher for specific Topic and send message)

ex: "mosquitto_pub -h 60.250.82.33 -t test -m 1234" means to send Topic as test and message is 1234 to the subscriber.

Module (EXS82-W):

AT command for publisher:

AT+COPS?

+COPS: 0,0,"Chunghwa Telecom",7

at^SICA=0,1

AT^SISS=1,srvType,"Mqtt"

AT^SISS=1,conId,"1"

AT^SISS=1,address,"mqtt://60.250.82.33"

AT^SISS=1,cmd,"publish"

AT^SISS=1,hcContLen,4

AT^SISS=1,clientId,"1111"

at^SISS=1,Topic, "test"

at^SISS?

^SISS: 0,"srvType",""

^SISS: 1,"srvType","Mqtt"

^SISS: 1,"conId","1"

^SISS: 1,"address","mqtt://60.250.82.33"

^SISS: 1,"cmd","publish"

^SISS: 1,"hcContLen","4"

^SISS: 1,"clientid","1111"

^SISS: 1,"topic","test"

^SISS: 2,"srvType",""

at^sica=1,1

AT^SISO=1

^SIS: 1,0,8800,"Mqtt connect 60.250.82.33:1883"

^SIS: 1,0,2500,"Connection accepted on clean session."

at^SISW=1,4

^SISW: 1,4,0

Result:

Module side: (After Sending at^SISW=1,4 command, type “abcd”)

Ubuntu side:

You can see the result like:

mosquitto_sub -h 60.250.82.33 -t test

abcd => Receive the message from publisher

Comment

veranith

Jan 31 2020 - 3:19pm

Hello Leon

That's a nice start :)

do you have an example use of the Dynamic setup, making use of ^SISD and ^SISU ?

I'm unable to make it work (I'm on a EXS82-W with REVISION 00.038).

"Static" setup with ^SISW works fine

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veranith

Feb 3 2020 - 3:29pm

Hi Leon

Some precisions / more details :

I'm testing with Cayenne Mydevices (https://developers.mydevices.com/cayenne/features/) where the topic name is a bit long.

Reminder : it works fine when I use the static method (SISO=x, SISW, SISC=x)

I've tried 2 methods for dynamic send (SISO=x,2) :

1/ ^SISU with arguments.

at^sisu=2,"publish","1:v1/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/things/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx/data/2:0:rel_hum,p=40:12"

+CME ERROR: text string too long

--> what's the maximum allowed size for this command ? is it possible to extend it ?

2/ ^SISD + ^SISU without arguments :

remark a/ looks like "GSM" coding is used (it doesn't make sense to me to use this coding schemen here):

at^sisd=2,"setParam","hcContent","rel_hum,p=100"

at^sisd=2,"getParam","hcContent"

^SISD: 2,"hcContent","rel\11hum,p=100"

remark b/ the documentation doesn't seem clear to me because I would expect to define everything with SISD and then just trigger the command with SISU, but SISU seems to expect from me to use SISW (I receive a ^SISW: 2,1 URC, then I write some data, which are transmitted, then I receive a SISW: 2,2 URC but the connection is maintained and I can send some more data, which looks like what I want. But it's a bit confusing).

--> I don't know if I understood well.