Hello talker001,
The filter is just a bit mask, so you can create a pattern to let only
one particular ID through, but as soon as you need multiple IDs you
would need to be less restrictive with that bit mask to let both IDs
through which in turn means you'll potentially get IDs that you don't
want.
Let's say both IDs (102 and 112) are decimal. As the filer is a bit
mask, a binary representation of the numbers is easier to understand.
So you would need a mask that lets
1100110 (decimal 102) and
1110000 (decimal 112)
through. Obviously, a single mask cannot work, but both IDs have to
following common bits: 11x0xx0. Thus, you can create a filter for all
IDs that match the 000011x0xx0 pattern. For the bits that can be either
or, the mask needs to be '0', so the mask looks like this:
11111101001 (decimal 2025)
The comparator needs to be 00001100000 (decimal 96). The bit
positions with the x don't matter as the mask is set to ignore those
bits and are set to '0'.
So the above filter configuration lets IDs pass that match the
000011x0xx0 pattern. That means that the filter will block all IDs but the follwoing ones:
00001100000 (decimal 96)
00001100010 (decimal 98)
00001100100 (decimal 100)
00001100110 (decimal 102)
00001110000 (decimal 112)
00001110010 (decimal 114)
00001110100 (decimal 116)
00001110110 (decimal 118)
Please note that if you are using Series 2 CAN hardware, you should use
the 'Series 2 Filter' attributes to set the filter bit masks rather
than the regular mask/comparator attributes (which are provided for compatibility
with Series 1 CAN hardware). The needed values for the Series 2 filters
are similar to the above ones; however you need to add 21 zeros at the
end:
Series 2 Mask: 11111101001000000000000000000000
Series 2 Comparator: 00001100000000000000000000000000
Set the 'Series 2 Filter Mode' to 0 (Single Standard).
-B2k
