LoRaWAN adds \n to binary value in JSON
Toni Juola
Petr Gotthard
Hi. I am not aware of this. Could you share the entire JSON please?
Petr
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Toni Juola
Fields#{ data => #{ test => [#{ value => Test }]}};
(Fields, _) ->
Fields
torstai 20. kesäkuuta 2019 18.33.16 UTC+3 Petr Gotthard kirjoitti:
Hi. I am not aware of this. Could you share the entire JSON please?
Petr
From: lorawan...@googlegroups.com [mailto:lorawan...@googlegroups.com] On Behalf Of Toni Juola
Sent: 20 June 2019 17:25
To: LoRaWAN Server Users <lorawan...@googlegroups.com>
Subject: LoRaWAN adds \n to binary value in JSON
Hi!
I was just wondering why LoRaWAN adds "\n" this to start of binary value in JSON ? How to overcome this? I am pretty sure there is some easy workaround but just can't figure out what it is.
Example: Binary value is "0000" but in JSON as it is sent from connector to application it is "\n0000"
If someone could figure this out I would be very grateful. Thanks in advance!
Br,
Stonde
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Toni Juola
Petr Gotthard
It’s a UNICODE character, thus ‘\uXXXX’.
You are likely inserting a non-printable binary value to a JSON, which is textual.
The default Uplink Fields get converted automatically, but if you want to have own field with a binary value, you need to convert it yourself using the “lorawan_utils:binary_to_hex” function, e.g.:
fun(#{port := 46}=Fields, <<Test:1/binary>>) ->
Fields#{ data => #{ test => [#{ value => lorawan_utils:binary_to_hex(Test) }]}};
(Fields, _) ->
Fields
end.
Alternatively, if it’s a binary-encoded number (integer or float), not a binary value, parse it as a number, not a binary value. See Section 4.3 in http://erlang.org/documentation/doc-6.4/doc/programming_examples/bit_syntax.html. For example:
fun(#{port := 46}=Fields, <<Test:8>>) ->
Fields#{ data => #{ test => [#{ value => Test }]}};
(Fields, _) ->
Fields
end.
Regards,
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Petr Gotthard
You likely send 8 bits, which is represented by 2 hex-digits. In which encoding you want these 4 digits?
It’s it’s bits, why don’t you parse it as bits? The Erlang binary parsing is super-powerful. If you are getting 1 byte (8 bits), where the first 5 bits are useless and then the last 3 bits indicate what you said, then you can do:
fun(#{port := 46}=Fields, <<_:5,Batt:1,Temp:1,Smoke:1>>) ->
Fields#{ data => #{ test => [#{ batt => Batt, temp => Temp, smoke => Smoke }]}};
(Fields, _) ->
Fields
end.
Petr
From: Toni Juola [mailto:juol...@gmail.com]
Sent: 20 June 2019 18:56
To: Petr Gotthard <petr.g...@centrum.cz>
Subject: Re: LoRaWAN adds \n to binary value in JSON
Or hmmmmm.... not completely. I need this "0000" as straight "0000". This converts it to: "00" and the other one to plain "0"
Here some description:
Bit 0: smoke alarm status: bit0=1 represents there is a smoke alarm, bit0=0 represents there is no smoke alarm
Bit 1: temperature alarm status, bit1=1 represents there is high temperature alarm, bit1=0 represents there is no temperature alarm
Bit 2: low battery voltage status, bit2=1 represents there is a low battery level alarm, bit2=0 represents there is no battery level alarm
The handling for the bits are done in the receiving side.
Br,
Stonde
to 20. kesäk. 2019 klo 19.48 Toni Juola (juol...@gmail.com) kirjoitti:
Thank you again Petr. You are the greatest. This one solved the issue: lorawan_utils:binary_to_hex(Test)
-Toni
To view this discussion on the web visit https://groups.google.com/d/msgid/lorawan-server/00d601d52786%24b085d740%24119185c0%24%40centrum.cz.
Petr Gotthard
So you are pretty advanced, I didn’t know, sorry J
lorawan_utils:binary_to_hex() encodes X bytes to 2X hexa-digits, so if you want 4 digits, you need to send 2 bytes
if you want “00XX”, where 00 is fixed and XX are hex-digits based on this 1-byte you can do
lorawan_utils:binary_to_hex(<<0,Test/binary>>)
which prepends additional byte before the 1-byte Test, so it will produce 2*(n+1) hexa-digits, where n is the number of bytes in Test
Am I missing something?
Petr
From: Toni Juola [mailto:juol...@gmail.com]
Sent: 20 June 2019 19:23
To: Petr Gotthard <petr.g...@centrum.cz>
Subject: Re: LoRaWAN adds \n to binary value in JSON
The reason why I dont parse as plain bits is because I need only some values as bits. And for those bit values I provide extra field binary that the receiving end knows that it needs its own parsing in the receiving side.
This is the complete handler structure currently:
fun(#{port := 46}=Fields, <<16#0101:16, Smoke:8, Temp:16/big-signed-integer, Hum:8/unsigned-integer, Bat:8, Alarm:1/binary, Fault:1/binary, Pollution:8, Wvol:8>>) ->
Fields#{ sensor => 'AN-102C', data => #{smoke => [#{ index => 0, value => (Smoke/100), unit => 'dBm' }], temperature => [#{ index => 0, value => (Temp/100), unit => 'celsius' }], battery => [#{ index => 0, value => Bat, unit => 'percent' }], alarm => [#{ index => 0, value => Alarm, unit => 'binary' }], fault => [#{ index => 0, value => Fault, unit => 'binary' }], test => [#{ index => 0, value => 'null', unit => 'binary' }]}};
(Fields, <<16#0102:16, Test:1/binary>>) ->
Fields#{ sensor => 'AN-102C', data => #{test => [#{ index => 0, value => Test, unit => 'binary' }], smoke => [#{ index => 0, value => 'null', unit => 'dBm' }], temperature => [#{ index => 0, value => 'null', unit => 'celsius' }], battery => [#{ index => 0, value => 'null', unit => 'percent' }], alarm => [#{ index => 0, value => 'null', unit => 'binary' }], fault => [#{ index => 0, value => 'null', unit => 'binary' }]}};
(Fields, <<16#0103:16, Alarm:1/binary, Fault:1/binary, Smoke:8, Temp:16/big-signed-integer, Hum:8/unsigned-integer, Bat:8, Pollution:8>>) ->
Fields#{ sensor => 'AN-102C', data => #{alarm => [#{ index => 0, value => Alarm, unit => 'binary' }], fault => [#{ index => 0, value => Fault, unit => 'binary' }], smoke => [#{ index => 0, value => (Smoke/100), unit => 'dBm' }], temperature => [#{ index => 0, value => (Temp/100), unit => 'celsius' }], battery => [#{ index => 0, value => Bat, unit => 'percent' }], test => [#{ index => 0, value => 'null', unit => 'binary' }]}};
(Fields, _) ->
Fields
end.
All would be perfect without the "\n" at the start of the binary values when sending forward as JSON. For example for the test it creates JSON like this:
{"data":{"alarm":[{"index":0,"unit":"binary","value":null}],"battery":[{"index":0,"unit":"percent","value":null}],"fault":[{"index":0,"unit":"binary","value":null}],"smoke":[{"index":0,"unit":"dBm","value":null}],"temperature":[{"index":0,"unit":"celsius","value":null}],"test":[{"index":0,"unit":"binary","value":"\u0000"}]},"datetime":"2019-06-20T17:21:51Z","deveui":"FFFFFF10000074BA","port":46,"sensor":"AN-102C"}
The only problem bolded. This is from the test button of the sensor.
-Stonde