reading float points

[davidoc85]

I was reading integer values good so far, however when trying to read float points, the message is encoded differently.

Example reading Temperature value using 2 registers and Float-BigEndian is giving me the following result: 17/11/2016, 15:14:09Indexlvl/1 : msg.payload : buffer [4]bf99999a So it is reading bf99999a. Can we add modbus the ability to support float points?

See nodes example below:

modbusfloat.txt

[hardillb]

You need to look at reading different data types from buffers: https://nodejs.org/dist/latest-v6.x/docs/api/buffer.html

The modbus node should not make any attempt to decode the values it gets back from the device, you need to do it in a function node down stream.

There was some discussion today at lunch about making a generic node that can unpack buffers into objects, but this is not something likely to be implemented soon

[davidoc85]

Would this help?

https://flows.nodered.org/node/node-red-contrib-protocolbuffersnode

[hardillb]

No, that is specific to Google's Proto buffer packing format

[davidoc85]

Please can you point me in the right direction with an example like how to convert a 0003 buffer value to a number so it can be plotted? How about a raw float value to a number?

I will get more informed meanwhile.

[hardillb]

It will depend if it's Little Endian or Big Endian. But something like this in a function node:

var float = msg.payload.readFloatLE() msg.payload = float return msg;

If that doesn't give a sensible number try swapping LE for BE at the end of readFloat