Signed Freeform CAN data variables
Hi,
we are using a new 50Hz GPS receiver which transmits its latitude and longitude each as a 32 bit signed integer using big endian format on a single 8 byte CAN ID.
We cant seem to find a way in the GUI to specify the data as signed? ( powervision 2.9 ) There is a big/little endian tick box, can we please request a 'signed' data tick box.
Many thanks.
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Thanks for the suggestion. The issue of big endian signed integers is something that hasn't been a big request. J1939 generally uses a parameter offset rather than signed data. J1939 and NMEA2000 typically use a little endian data format.
A way to work around would be to receive the message with a Free Form Numeric Message and then use two's complement to convert the negative values. For instance this can be done for 32 bit values in a calculation event:
You probably have already something similar. I put it in for other readers too.
If somebody else would like to see this feature added please leave a comment so the higher powers will know you want it.
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I guess something very similar to the Library J1939/NMEA tab, where all the requird data can be specified as you would find in a dbc file, including signed data, would be really nice if the same functioanlity was ported to the freeform can area. :)
Which got we wondering, should all freeform CAN be specified in the Library tab like above, and then only the variable binding to the physical port and a psudo device name be done in the connections area where you would select the protocol type, freeform for example?
Cheers, Dave.
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I agree with Dave - the ability to specify CAN messages/signals as you would in a .dbc file would be hugely valuable for development in environments that do not use J1939 or NMEA2000. Ideally a .dbc parser would be included so you could just select the messages you want to read and the associated signals are automatically generated.
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