Function to cut text message

Hello everyone.

On the Raspberry Pi I connect to the USB input a module that has 8 A/D inputs.
The module sends to the serial port every 500 MS the reading of 8 channels in analog input.
I need a function that will filter the channel I use let's say ch1
Which function will do this?
this is a sample reading "
"CH1: 2004 > 1.645V"
"CH2: 2134 > 0.640V"
"CH3: 2304 > 1.145V"
''
"CH8: 3304 > 1.005V"

I need to send just the "CH2: 0.640V"
thanks

Are these seperate msg's? If so, and if the string is in msg.payload, you could use a switch node to use the 'contains' option and compare it to the channel number you want to pass thru, like 'CH2'

Are you sure you want a string
"CH2: 0.640V"
and not a javascript object
{CH2: 0.64}
which, if it was in msg.payload, would allow you to use msg.payload.CH2 to access the value 0.64

The module send every 500msec the all 8 analog value of his input at once message.
With using Switch I thing I can’t do it

How have you configured the serial port? Try setting it to split on \n and it may give you separate messages. If that doesn't work feed the message into a debug node and show us what it looks like.

Thanks I will try it tomorrow and will report about it