Siemens HMI (char & string) question

Hi Guys,

I'm hoping for a bit of help with this one please as I am not very experienced in the world of Siemens stuff !

PLC Siemens S7-300 CPU314, Siemens HMI TP177B

I'm working with a barcode scanner which puts 4 off "characters" (data type CHAR) into a DB to work with.

For diagnostic purposes I want to show these characters on my local HMI so that the site can check that the barcode scanner is working.

But ....... there doesn't seem to be a CHAR data type in the HMI, I can only see a STRING data type.

How would I put / turn these four characters into a STRING that I could then show ?

Many thanks,

Mark.

I think you mean that there is a CHAR tag type, but no way to display with CHAR format.

Try this:

Create a STRING[4], in both the PLC and HMI.
Bytes 0 and 1 is the full length and used length. Dont touch these.
Manually load the character bytes into bytes 2..5.

// STRING[4] starts at DB10.DBB0
L "scannerbyte_0"
T DB10.DBB2
L "scannerbyte_1"
T DB10.DBB3
L "scannerbyte_2"
T DB10.DBB4
L "scannerbyte_3"
T DB10.DBB5

Or you could just use the String tag type, starting at the start char and using a fixed length of 4.
Which can be configured in the General > Settings and Properties tabs

No dont start the STRING tag at the address of the 1st CHAR. The 1st CHAR must be the 3rd byte of the STRING tag, and so forth.

Jeebs said:

Or you could just use the String tag type, starting at the start char and using a fixed length of 4.
Which can be configured in the General > Settings and Properties tabs

Click to expand...

Thanks JesperMP I have changed both the PLC and HMI as you have suggested.

As this is a remote site to me (in Denmark actually !) I have to connect via a VPN.

I have successfully connected and downloaded the new blocks to the PLC, and I can monitor to check things look okay, but WinCC flexible won't let me connect to the HMI and download the updated program - it tells me that it cannot connect and I must check my settings etc.

Now, nothing has changed since I was last on site and I can successfully connect to the PLC (all devices are on ethernet by the way), can you suggest where I may be going wrong and why I cannot connect to transfer the HMI program ?

Many thanks,

Mark.