eryksun added the comment:
No, ctypes.Structure should use native endianness. So on a little-endian it's
the same as ctypes.LittleEndianStructure, and on a big-endian system it's the
same as ctypes.BigEndianStructure. ARM processors can work in either mode.
IIRC, the Raspberry Pi is built as
eryksun added the comment:
It seems you want a BigEndianStructure:
from ctypes import *
class SAEJ1939MsgId(BigEndianStructure):
_fields_ = (('reserved', c_uint8, 3),
('priority', c_uint8, 3),
('extended_data_page',
zeero added the comment:
Thanks for the advise. I'll give it a try.
So ctypes.Structure is always little endian regardless from the underlying
architecture.
I just checked on a raspberry pi 2 that should be a big endian device, and got
the same results as before.
I'm still not sure if it's
zeero added the comment:
Sorry for the inconvenience.
The format specification can be found in chapter 2.1 in
http://vector.com/portal/medien/cmc/application_notes/AN-ION-1-3100_Introduction_to_J1939.pdf
So I would write down the field contents in that order
_fields_ =
Martin Panter added the comment:
It would be helpful if you could trim down your example code a bit. Without
studying the whole file, it is hard to see exactly what order you are seeing
and what order you expect, since there are two versions with different orders
in the code.
My
