Cubecell payload problems

haggishm · March 3, 2020, 6:42am

After some advice please to decode the payload from the cubecell LoRaWan BMP280 example.

I have Chirpstack running on RakWireless Gateway. Within node-red I have extracted the payload data field, applied base64 decryption and have the hex output but can’t work out how to get the decimal results from this.

Battery level is the last two bytes, which are 0x10 and 0x60, this as 0x1060 is the correct voltage od 4.162 but this system does work for other values for example Pressure reading is 1004.57 hpa. These are the hex bytes for pressure 03 2c 7b 44 I don’t know how to get the correct result from this.

Any help appreciated.

Thanks
Craig

wasn · March 3, 2020, 7:02am

Have look at this Decoder

github.com

HelTecAutomation/ASR650x-Arduino/blob/master/libraries/LoRa/examples/LoRaWAN/LoRaWAN_Sensors/LoRaWan_MultiSensor/TTN/chirpstack-decode.js

function bytesToInt(by) {
  f = by[0] | by[1]<<8 | by[2]<<16 | by[3]<<24;
  return f;
} 

function bytesToFloat(by) {
  var bits = by[3]<<24 | by[2]<<16 | by[1]<<8 | by[0];
  var sign = (bits>>>31 === 0) ? 1.0 : -1.0;
  var e = bits>>>23 & 0xff;
  var m = (e === 0) ? (bits & 0x7fffff)<<1 : (bits & 0x7fffff) | 0x800000;
  var f = sign * m * Math.pow(2, e - 150);
  return f;
} 

function Decode(port, bytes) {

var decoded = {};
i = 0;
//decoded.AppDataSize = bytes.length;

This file has been truncated. show original

haggishm · March 3, 2020, 7:41am

Hi, Thank you for your quick reply, I have tried that before, is there any preprocessing that needs to be done to get from msg.payload.data to this decoder, how should it be called?

Thanks in advance
Craig

haggishm · March 3, 2020, 7:58am

This is what I get from mqtt in node-red

object
applicationID: “4”
applicationName: “CubeCell”
devEUI: “2232330000888802”
deviceName: “dev-2232330000888802”
timestamp: 1583221828
fCnt: 7
fPort: 2
data: buffer[26]
data_encode: “base64”
object: object
adr: true
rxInfo: array[1]
txInfo: object

This is the buffer expanded, I have turned off all data except pressure and battery level bytes.

data: buffer[26][raw]
[0 … 9]
0: 0x0
1: 0x0
2: 0x0
3: 0x0
4: 0x0
5: 0x0
6: 0x0
7: 0x0
8: 0x0
9: 0x0
[10 … 19]
10: 0x0
11: 0x0
12: 0xd2
13: 0x2f
14: 0x7b
15: 0x44
16: 0x0
17: 0x0
18: 0x0
19: 0x0
[20 … 25]
20: 0x0
21: 0x0
22: 0x0
23: 0x0
24: 0x10
25: 0x40

Bytes, 12-15 are pressure reading 1004.90 and bytes 24 and 25 are battery level is 4166 which is 0x1040 in hex. Do I need to convert from the buffer to be able to use your decoder?

Thanks
Craig