Protocol Scan Function

[PH from Brazil]

Dear, how are you? I have a problem and would appreciate any help.

I use a serial port from Visio 230 to read data from a Vaisala WXT520 weather station. It´s all right but the rain message. I´ll explain.

I receive repeatdly the rain message in the following format:

0R3,Rc=9.9M,Rd=8s,Ri=7.7M,Hc=6.6M,Hd=5s,Hi=4.4M,Rp=9.9M,Hp=2.2M<CR><LF>

But dependent on the intensity of rain, the message changes its long and may be like this

0R3,Rc=19.9M,Rd=18s,Ri=27.7M,Hc=16.6M,Hd=25s,Hi=14.4M,Rp=91.9M,Hp=22.2M<CR><LF>

In resume: only the dividers are constant, but the numbers are not. The message lenght changes because of numbers change.

How can I use Protocol Scan to read this message "all the time", independent on values or string length?

I tried to use 8 Variables at the configuration protocol to this message, but it not worked.

Some doubts:

- What configurations may I do on message properties? I tried to use Numeric, Decimal ASCII with no fixed length, with No Prefix. It should be working?

- When I use only one variable to transfer all the message to, it worked, but it´s very difficult solve the values when the positions are not fixed.

[Simon]

There are a few of options I have used.

1. Check the features of the Vaisala instrument - maybe you can change the numeric format to have "leading zeroes". That will make the numeric fields always have a constant length.

2. Determine the number of different possible messages based on the different length numeric variables that can be sent. If there are not "too many" different messages then create a protocol scan message for each different option. When the input message is received the PLC will match it to the scan message that fits.

3. If there are too many variations to use option 2, then the only other option is to use the "stream" variable type to catch the string as a stream and decode it using ladder programming. This is by far the more complex option, so I would look very closely at whether you can solve it with option 2 above.

[Gabriel Franco]

So, just using protocol scan FB, It's not possible to get numeric data with different lengths even there's control char or any other characters as a separation between values ?

I have a similar issue, 5 values to get, all numeric, all with different lengths, so, there's so many combinations.

Decimal ASCII no fixed length confuses me.

[Ag Automation]

I am using a V130 to control irrigation and control greenhouse climate. I would like to add weather sensors, wind speed, direction, rainfall amounts to the PLC so that i can automatically make adjustments based on outside weather. and suggestions where to find such sensors? It would not need to be highly accurate.

[AlexUT]

Ag Automation,

Please open a new topic.

This will help to organize Q&As.

Thanks.

[Joe Tauser]

You're going to have to read the whole string and parse it in logic by searching for the commas and breaking it into pieces. Then you can use the ASCII->NUM functions to get your numbers out.

I just went through this with a comma separated barcode that had variable fields like yours. It wasn't too bad once I figured out what I had to do. Post your code and maybe we can help.

Joe T.

[razor_rich]

Hi,

 

I need some help with the Protocol Scan FB.  I'm reading the following output from a scale, and I just need to get the weight (the XXXXX.XX part).  Can anybody advise me on how to setup the "Protocol Message" in the Protocol Scan FB?

 

[razor_rich]

Via Termite (http://www.compuphase.com/software_termite.htm), I'm getting the following string:

 

[02]   402.2LG 

 

There is a space (aka "<SP>") on the end of that string for the "status" field.  

 

The weight is 402.2.  I need to extract this weight from the string and store it with my V130.

 

The "L" is for "pounds" and the "G" is for "gross."  I'm assuming the "[02]" indicates the <STX> control character.

[razor_rich]

I'm trying to figure this out on my own, but a key sentence in the Help manual is missworded.  Can somebody please explain to me in plain English what the third green call-out box is trying to say?

 

[Gabriel Franco]

Try this way.

 

Set MI523 = 10 (1 decimal place) and use an ML instead MI to link your weigh value.