Documentation for Downlink from Mqtt client

ChirpStack Application Server
1

I’ve been using an mqtt client for a while to send downlinks to my sensors, but I’ve noticed lately that the Gateway always sends at the same frequency, and I would like to be able to control the send frequency, or the mode ADR is enabled, but by adding the frequency in my json file, the server application does not take it into account. I have the impression that it is just the field “data” and “fport” which are taken into account…

there is my json data that is sent via mqtt to the application server :

{"frequency":"867300000","confirmed":false, "fPort":46,"data":"af////+AAAA="}

on API Application server :

jj
jj1065×748 126 KB

there is any documentation that descripe all the element we can add on the mqtt message and how writ it on the good format ?

2

The used frequency is defined by the network-server, not by the end-user and depends on how the downlink is scheduled (Class-A, Class-B or Class-C) and if the downlink is scheduled as RX1 or RX2 (Class-A). In other words, you enqueue (through the AS) a payload to be transmitted by the NS and the NS decides which TX parameters to use for transmitting this payload.

I recommend to take a look at the LoRaWAN Regional Parameters specification.

1 Like
3

Thanks for the information ! i will check more informations in the LORAWAN spécification.

4

I have same issue, I see the downlink but i does not appear in my node. please what do i do here

5

Hello sir,

How can I use mqtt to send downlink to chirpstack application server
can you please help me out with downlink to send the data.

6

You do not even give information about your application, or where it’s located and with what programming language, sorry but you have to be more rigorous than that in your work, how do you want us to help you.

7

See “Scheduling a downlink.”

8

Thanks @bconway , but did not work in my case. when I try this command, mosquitto server receives info, but no info goes to app_server, some ideas ?

mosquitto_pub -h my.chirpstack.server -t “application/9/device/dev_eui_DEAD_BEEF/command/down” -m “{“confirmed”: false, “fPort”: 1, “data”: “pgE=”}” -u username -P ‘password’ -d

9

Sorry… review logs, the info ARRIVES to app_server, but with this error…

time=“2021-03-22T17:38:09Z” level=error msg=“integration/mqtt: tx payload unmarshal error: invalid character ‘â’ looking for beginning of object key string” data_base64=e+KAnGNvbmZpcm1lZOKAnTpmYWxzZSzigJxmUG9ydOKAnTogMSzigJxkYXRh4oCdOuKAnHBnRT3igJ19

10

Well it’s fixed !!!

It was a single and double quotes problem.

Thanks and regards !!