Help with a codec

1

Hi,

I need some help to add some parameters to an existing working codec.

I am already retrieving the alert flags which result in a number like so

alert_flags:2048

the details of this perameter are:

Parameter: Alerts Flags
Length: 2
Description: Bit Map of Alerts Volcano flags LSB First

I then have a table representing the bits. What I need is one additional parameter which is bit 3

How do I achieve this in the chirpstack codec? I think I need to convert to binary first?

Any help would be greatly appreciated

2

This guide may help you.

The node will need to upload the integer as two bytes.
Then the codec will convert the two bytes back to integer.

3

ok, I think I got it. if anyone can spot anything wrong, please let me know

// Decode decodes an array of bytes into an object.
//  - fPort contains the LoRaWAN fPort number
//  - bytes is an array of bytes, e.g. [225, 230, 255, 0]
//  - variables contains the device variables e.g. {"calibration": "3.5"} (both the key / value are of type string)
// The function must return an object, e.g. {"temperature": 22.5}
function Decode(fport, bytes, variables) {
  console.log(bytes)
  var decoded = {};
  var frame_id = bytes[0];
  decoded.frame_id = frame_id;
  var firmware_version_1 = bytes[1];
  decoded.firmware_version_1 = firmware_version_1;
  var firmware_version_2 = bytes[2];
  decoded.firmware_version_2 = firmware_version_2;
  var eu_rssi = bytes[3];
  decoded.eu_rssi = (256 - eu_rssi) * -1;
  var last_stored_read = ((bytes[4] << 0) & 0xFF) + ((bytes[5] << 8) & 0xFFFF) + ((bytes[6] << 16) & 0xFFFFFF) + ((bytes[7] << 24) & 0xFFFFFFFF);
  decoded.last_stored_read = last_stored_read;
  var factor = bytes[8];
  decoded.factor = factor;
  var last_dl = (bytes[10] << 8) | bytes[9];
  decoded.last_dl = last_dl; 
  var dl_interval = (bytes[12] << 8) | bytes[11];
  decoded.dl_interval = dl_interval;
  var alert_flags = (bytes[14] << 8) | bytes[13];
  decoded.alert_flags = alert_flags;
  var battery_level = (bytes[16] << 8) | bytes[15];
  decoded.battery_level = battery_level / 1000;
  var number_of_deltas = (bytes.length - 17) / 2;
  decoded.number_of_deltas = number_of_deltas;
  var water_volume = decoded.last_stored_read * decoded.factor
  decoded.water_volume = water_volume;
  
  // Call the decodeVolcanoFlags function to decode the volcano alert flags
  const volcanoFlags = decodeVolcanoFlags(bytes, 15);
  decoded = { ...decoded, ...volcanoFlags }; // Add the decoded flags to the decoded object

  return decoded;
}

// Decode the 2-byte bitmap starting from the specified offset
function decodeVolcanoFlags(bytes, offset) {
  const flags = {};

  const bitmap = (bytes[offset + 1] << 8) | bytes[offset];

  // Loop through each bit in the bitmap and extract the alert flag
  for (let i = 0; i < 16; i++) {
    const alertNumber = i + 1;
    const bitValue = (bitmap & (1 << i)) >> i;
    flags[`alert${alertNumber}`] = Boolean(bitValue);
  }

  return flags;
}

Thanks for your help

4

execute js error: js vm error: (anonymous): Line 35:3 Unexpected reserved word (and 9 more errors

5

is there a secret to merging

decoded = { ...decoded, ...volcanoFlags }; // Merge the decoded and volcanoFlags objects

this seems to be throwing this error:


"execute js error: js vm error: (anonymous): Line 31:18 Unexpected token . (and 11 more errors)"

I have also tried

decoded = Object.assign({}, decoded, volcanoFlags);

But that is also in error. I have checked and can’t seem to see where I am going wrong any help would be greatly apprecaited. Herewith my latest version.

by the way, this if for an Arad Water meter. I have looked everywhere but can’t find a decent codec anywhere and hence trying to get this to work


function Decode(fport, bytes, variables) {
    console.log(bytes)
    var decoded = {};
    var frame_id = bytes[0];
    decoded.frame_id = frame_id;
    var firmware_version_1 = bytes[1];
    decoded.firmware_version_1 = firmware_version_1;
    var firmware_version_2 = bytes[2];
    decoded.firmware_version_2 = firmware_version_2;
    var eu_rssi = bytes[3];
    decoded.eu_rssi = (256 - eu_rssi) * -1;
    var last_stored_read = ((bytes[4] << 0) & 0xFF) + ((bytes[5] << 8) & 0xFFFF) + ((bytes[6] << 16) & 0xFFFFFF) + ((bytes[7] << 24) & 0xFFFFFFFF);
    decoded.last_stored_read = last_stored_read;
    var factor = bytes[8];
    decoded.factor = factor;
    var last_dl = (bytes[10] << 8) | bytes[9];
    decoded.last_dl = last_dl;
    var dl_interval = (bytes[12] << 8) | bytes[11];
    decoded.dl_interval = dl_interval;
    var alert_flags = (bytes[14] << 8) | bytes[13];
    decoded.alert_flags = alert_flags;
    var battery_level = (bytes[16] << 8) | bytes[15];
    decoded.battery_level = battery_level / 1000;
    var number_of_deltas = (bytes.length - 17) / 2;
    decoded.number_of_deltas = number_of_deltas;
    var water_volume = decoded.last_stored_read * decoded.factor
    decoded.water_volume = water_volume;

    // Call the decodeVolcanoFlags function to decode the volcano alert flags
    var volcanoFlags = decodeVolcanoFlags(bytes, 15);
    decoded = { ...decoded, ...volcanoFlags }; // Merge the decoded and volcanoFlags objects

    return decoded;
}

// Decode the 2-byte bitmap starting from the specified offset
function decodeVolcanoFlags(bytes, offset) {
    var flags = {};

    var bitmap = (bytes[offset + 1] << 8) | bytes[offset];

    flags.tamper = !!(bitmap & 0x01); // Bit 0 represents alert 1
    flags.cut_wire = !!(bitmap & 0x02); // Bit 1 represents alert 2
    flags.battery = !!(bitmap & 0x04); // Bit 2 represents alert 3
    flags.leak = !!(bitmap & 0x08); // Bit 3 represents alert 4
    flags.ccw = !!(bitmap & 0x10); // Bit 4 represents alert 5
    flags.power_down = !!(bitmap & 0x20); // Bit 5 represents alert 6
    flags.field_configuration = !!(bitmap & 0x40); // Bit 6 represents alert 7
    flags.res = !!(bitmap & 0x80); // Bit 7 represents alert 8
    flags.low_temp = !!(bitmap & 0x0100); // Bit 8 represents alert 9
    flags.qmax = !!(bitmap & 0x0200); // Bit 9 represents alert 10
    flags.poor_rf = !!(bitmap & 0x0400); // Bit 10 represents alert 11
    flags.dl_active = !!(bitmap & 0x0800); // Bit 11 represents alert 12
    flags.dl_mem_err = !!(bitmap & 0x1000); // Bit 12 represents alert 13
    flags.dl_delta_of = !!(bitmap & 0x2000); // Bit 13 represents alert 14
    flags.dl_delta_size = !!(bitmap & 0x4000); // Bit 14 represents alert 15
    flags.res2 = !!(bitmap & 0x8000); // Bit 15 represents alert 16

    return flags;
}
6

I finally got it working …

This is the codec for Arad water meters. It works on both Gladiator and Octave ranges.

They are pricey, but solid, utilities grade meters.

function Decode(fport, bytes, variables) {
    console.log(bytes)
    var decoded = {};
    var frame_id = bytes[0];
    decoded.frame_id = frame_id;
    var firmware_version_1 = bytes[1];
    decoded.firmware_version_1 = firmware_version_1;
    var firmware_version_2 = bytes[2];
    decoded.firmware_version_2 = firmware_version_2;
    var eu_rssi = bytes[3];
    decoded.eu_rssi = (256 - eu_rssi) * -1;
    var last_stored_read = ((bytes[4] << 0) & 0xFF) + ((bytes[5] << 8) & 0xFFFF) + ((bytes[6] << 16) & 0xFFFFFF) + ((bytes[7] << 24) & 0xFFFFFFFF);
    decoded.last_stored_read = last_stored_read;
    var factor = bytes[8];
    decoded.factor = factor;
    var last_dl = (bytes[10] << 8) | bytes[9];
    decoded.last_dl = last_dl;
    var dl_interval = (bytes[12] << 8) | bytes[11];
    decoded.dl_interval = dl_interval;
    var alert_flags = (bytes[14] << 8) | bytes[13];
    decoded.alert_flags = alert_flags;
    var flags = {};
    var bitmap = (bytes[14] << 8) | bytes[13];
    flags.tamper = !!(bitmap & 0x01);
    flags.cut_wire = !!(bitmap & 0x02);
    flags.battery = !!(bitmap & 0x04);
    flags.leak = !!(bitmap & 0x08);
    flags.ccw = !!(bitmap & 0x10);
    flags.power_down = !!(bitmap & 0x20);
    flags.field_configuration = !!(bitmap & 0x40);
    flags.res = !!(bitmap & 0x80);
    flags.low_temp = !!(bitmap & 0x0100);
    flags.qmax = !!(bitmap & 0x0200);
    flags.poor_rf = !!(bitmap & 0x0400);
    flags.dl_active = !!(bitmap & 0x0800);
    flags.dl_mem_err = !!(bitmap & 0x1000);
    flags.dl_delta_of = !!(bitmap & 0x2000);
    flags.dl_delta_size = !!(bitmap & 0x4000);
    decoded.flags = flags;
    return decoded;
}
1 Like
7

The codec is basically JavaScript.
The codec should be in simple JavaScript.
Glad you can make it working.