Created attachment 565 [details]
code example in python

I own a Voltcraft K204 temperature datalogger for k type thermocouples.
https://sigrok.org/wiki/Voltcraft_K204

If i read temperatures via libsigrok e.g. via smuview (https://github.com/knarfS/smuview) i get nonsense values in negative temperatur range.

I dont really understand C code, but the protokoll seems to be implemented in https://sigrok.org/gitweb/?p=libsigrok.git;a=blob;f=src/hardware/center-3xx/protocol.c

I wrote a tiny python script to decode the positive temperatures (eg. T1) this way:

if data(byte8) < 240: T1 = (data[byte8]*256 + data[byte9])*0.1

For negative temp values i have to do:

if data(byte1) >= 240: T1 = ((data[byte8]-255)*256 + (data[byte9]-256))*0.1

It looks a bit weired, but i get right values over the whole temp range.

Byte 4 to 7 contains some status Bits fpr channel 1-4. 
Byte 4, Bit 2 -> T1 "OL"
Byte 4, Bit 1 -> T1 "normal Operation"

and so on.

I attached my python script. Maybe there is somebody who can fix decodeing negative temperatures in libsigrok.