0

I have multiple Modbus variables that I am trying to store on my local disk.

enter image description here

My function script is as follows:

var msgPortBus,msgStbdBus;
if (msg.topic === 'BusVolts') {
    msgPortBus = { payload: msg.payload.Port.Bus.Volts, };
    msgStbdBus = { payload: msg.payload.STBD.Bus.Volts, };
}
msg.payload = [msgPortBus,msgStbdBus]

return msg;

I assume the error is in the code above somewhere.... The topics for both Modbus nodes are 'BusVolts'.

I had used the following code for one input, which gives me my timestamp and then the data I would like from one input, but I was not sure how to differentiate between different payloads. 

msg.payload = new Date().toString() + 
    "," + msg.payload;
return msg;

Thanks in advance.

EDIT: Error is "Type Error: Cannot read property 'Bus' of undefined"

Infernez
  • 73
  • 7

1 Answers1

2

The problem is that you are assuming that the when the function node runs it will see a combined msg object that contains the information from both modbus nodes. This is not the case.

The function node will run separately for each output message from the modbus nodes, so only one of the msg.payload.Port.Bus.Volts or msg.payload.STBD.Bus.Volts will be populated at a time.

If you want to combine the output of multiple nodes before feeding it into the function node you will need to look at either storing data in the Context or using the Join node to batch the outputs together into an array before processing it.

hardillb
  • 54,545
  • 11
  • 67
  • 105
  • Thank you for this, this seems to work. However I have crashed my server with the following error being expressed: `25 Jun 15:56:48 - TypeError: "list" argument must be an Array of Buffer or Uint8Array instances` I tried to set it to a buffer, trial and error. Do you know how I can rectify this? – Infernez Jun 25 '18 at 15:21