Decoding data on chirsStack

Nabila · August 4, 2021, 12:52pm

Hello,
I need your help please! I don’t found a function to converter base64 to hexa. I have tried to do it with parseInt() but it gives false result. for exemple it give me 15 for F, while F must be 17 in hexa.

Thenk you

eugenev · August 4, 2021, 1:03pm

where and on which language. please specify.

Nabila · August 4, 2021, 1:10pm

in JavaScript with Node Js

alwint3r · August 5, 2021, 9:20am

Hello,

Are you trying to decode data on a separate application written in JS and use Node.js rather than using the decoder function in the ChirpStack Application Server? Because ChirpStack Application Server does not use Node.js as far as I know.

If you are indeed trying to convert the base64 string to an array of hexadecimal numbers using Node.js, you should see this documentation of Buffer in Node.js. You can use the base64 encoding when converting from base64 string using Buffer.

Nabila · August 5, 2021, 11:27am

Thank you for your rethink.
Indeed,i realized afterwards that i had to use the " BUFFER". Now I try to check just the code working on Node Js before copying it on ChirpStack. I hope there won’t be much difference between the two.

Good day

donsez · August 10, 2021, 12:56pm

Hi, I’m using these functions for replacing Buffer’s ones

github.com

CampusIoT/payload-codec/blob/master/src/main/ttn_chirpstack/buf.js

// Javascript functions for décoding and encoding the frame payloads
// From https://github.com/feross/buffer/blob/master/index.js

function readUInt16LE (buf, offset) {
  offset = offset >>> 0;
  return buf[offset] | (buf[offset + 1] << 8);
}

function readUInt16BE (buf, offset) {
  offset = offset >>> 0;
  return (buf[offset] << 8) | buf[offset + 1];
}

function readInt16LE (buf, offset) {
  offset = offset >>> 0;
  var val = buf[offset] | (buf[offset + 1] << 8);
  return (val & 0x8000) ? val | 0xFFFF0000 : val;
}

function readInt16BE (buf, offset) {

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Nabila · August 11, 2021, 6:08am

Thank you for your replay

Nabila · August 11, 2021, 6:19am

Hello,
Ineed your help please!

I am looking for a fonction to round to the unit(fonction equivalent to “Math.round()”) and fonction tohave two digits after the decimal point(fonction equivalent to “toFixed(2)” , which i can use in ChirpStack.

Good Day

eugenev · August 11, 2021, 11:52am

Nabila · August 11, 2021, 12:52pm

Thank you for your replay, but this fonctions are not recognized in chirpStack:(

Moss · August 16, 2021, 6:16pm

Try this one:
var result = “”;
for(var i = 0; i < bytes.length; ++i){
result+= (String.fromCharCode(bytes[i]));
}
var decodedStr = (result).toString(‘base64’);

Nabila · August 17, 2021, 6:12am

Thank you for your replay,i try this one