Data format for hex answer

[Yoruk]

Hello there,

I have issues to create the good data format mask to extract the data received from an RS-232 device.

The communication is working fine :

But I didn't manage to set up a good format mask.

Here is the answer, in hex :

01 04 02 00 1B F9 3B

I want to keep only the bytes 4 and 5 (in bold in this example). The first 3 ones are header, the two last are CRC, so I can skip them.

I tried this :

6x 4ah 4x

But doesn't works. Maybe because this syntax works only with ascii characters ?

I tried to find a suitable sample in the help, but I didn't find anything.

Is there a way to skip bytes ?

Thanks in advance !

[Yoruk]

Ok I tried to use

"\x01\x04\x02"2ah

as data format mask. Regarding the RS232 monitor my data is correctly detected :

So my data (in red) is 0x00 0x1B , which is correct. But why the output is still 0 ?? 

0x00 0x1B should be 27 in decimal...???

[hw70]

You need to read the last two bytes, too, to complete analysing the entire message.

Instead of '2ah' try 'i' (for signed short int) oder 'w' (word -- unsigned short), or 'iy' / 'wy' (Big-Endian versions).

Add another channel, read one 'i' (two byte), but do not connect the output, just read the bytes and ignore the output of the message's last two bytes.

[Yoruk]

Many thanks !

So I created a second channel, with only "i" as a measurement data format.

Going into the RS232 monitor, I now have a value : 😀

But I don't see why the data value is 0.15353E05. My incoming data is "00 1B" in hex so I should have 27 in decimal...?

[hw70 · Accepted solution]

Because '2ah' ist not correct, use i, w, iy, or wy instead, please.

One uses 'ah' as format string if a device sends hex numbers as ASCII text, e.g. 'F1<CR>' (= 241dec).

That would be "46 31 0D" as hex. (ASCII table 'F' = 46h, '1' = 31h, '<CR>'=0Dh).

But that is not the case for your example, you can interpret the bytes... "directly".

[Yoruk]

Ok I got it !

So finally I used

"\x01\x04\x02"iy2x

And it works directly, even if I don't have anymore the color highlighting :

The output value is now ok ! And thanks to the last "2x" in the mask I didn't need a second channel to finish reading the data ! 😀

Thanks a lot for your help !