Node-red Convert Hex number into signed floating number

[Akshay Bhavsar]

Hi there,

How can I convert Hex number into signed floating number in node-RED ?
I have tried parseInt(a,16), but it doesn’t work.

Thanks

[Peter Ferland]

That should work. Are you using a LoRa input node? If so, go to the node’s configuration and confirm that it is in byte mode and not UTF-8 mode.

[Akshay Bhavsar]

It is in byte mode, but doesn’t give me any data. Is there any alternative ?

[Peter Ferland]

Can you post the node red flow?

[Akshay Bhavsar]

Here is the flow

var longitude= ((msg.payload).slice((msg.payload.length)-4,msg.payload.length));
longitude = parseInt(longitude,16);
return longitude;

https://drive.google.com/open?id=0B8vP1Z3v0Sw8NHpvZ2ZlUGZVOXM

[Peter Ferland]

Ok, can you post the output of a debug node on output of the LoRa node?

[Akshay Bhavsar]

The output of debug node, without the function is as follow

00820dfdbd803008a08856

I want to slice 4 hex number at the end and convert it into decimal.
I just found that slice doesn’t written data type in hex. If I just assign hard value of hex number as
var a = 0xfb5216ff

It does convert into number by using parseInt command.

[Akshay Bhavsar]

Hi Peter,

Have you find anything ?

Thanks
Akshay

• This reply was modified 7 years, 2 months ago by Akshay Bhavsar.

[Akshay Bhavsar]

Hi there,

I have solved this by using following command.

var battery = ((msg.payload).slice((msg.payload.length)-9,(msg.payload.length)-8));
var rBuf_battery = new Buffer(battery,'hex');
var battery_val = (rBuf_battery.readInt8(0));

readInt8(0) function can be readUInt8(0) for unsigned number. Also depending the length of hex number this function can also be write as readInt16(0) and readInt32(0).

Thanks

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