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ferrumvir
Joined: 01 Feb 2006
Posts: 64
Location: England
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| CAN Filters issue |
 Posted: Wed May 30, 2007 3:48 pm |
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Hi,
With setting the most restictive mask (0x07FF, all 11bits) for RX0MASK, I only recieve messages through RXFILTER0 (i.e. recieve only rxid1), and do not recieve rxid2?
If I set the mask to 0x00FF then I recieve messages, rxid1 & rxid2. But this means slackening off the filter and allowing many more though.
My two rxIDs are 0x0203 and 0x0503 (b01000000011 and b10100000011, bits 11,10,8 are different), all three bits for the different masks.
| Code: |
void can_filt( int16 rxid1,rxid2,rxid3,rxid4,rxid5,rxid6 )
{
can_set_mode(CAN_OP_CONFIG);
can_set_id(RX0MASK, 0x07FF, 0); //set mask 0 // MATCH MASK 100%
can_set_id(RX0FILTER0, rxid1, 0); //set filter 0 of mask 0
can_set_id(RX0FILTER1, rxid2, 0); //set filter 1 of mask 0
can_set_id(RX1MASK, 0x07FF, 0); //set mask 1 // MATCH MASK 100%
can_set_id(RX1FILTER2, rxid3, 0); //set filter 0 of mask 1
can_set_id(RX1FILTER3, rxid4, 0); //set filter 1 of mask 1
can_set_id(RX1FILTER4, rxid5, 0); //set filter 2 of mask 1
can_set_id(RX1FILTER5, rxid6, 0); //set filter 3 of mask 1
can_set_mode(CAN_OP_NORMAL);
}
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Compiler 3.249, PIC18F2680, CAN 2.0A (i.e. standard 11bit IDs only),
Can anyone explain why the filter mask is causing issues?
Am I missing something?
I've read | Quote: | | For RBX0, two checks are made since it has two acceptance filters. |
on http://www.elecdesign.com/Articles/Print.cfm?AD=1&AD=1&AD=1&ArticleID=10925, but I don't understand how this would work, and having re-read the PIC data sheet understand that should either filter and mask be accepted then the message is written to the buffer. I think this is just confusing my understanding!
Cheers Scott |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed May 30, 2007 4:29 pm |
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| Quote: | | void can_filt( int16 rxid1,rxid2,rxid3,rxid4,rxid5,rxid6 ) |
There's a problem in the line of code above. You're making an
assumption about data type declarations in the parameter list.
Read the section on "parameter list" near the top of this C language guide.
http://www.acm.uiuc.edu/webmonkeys/book/c_guide/1.3.html |
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ferrumvir
Joined: 01 Feb 2006
Posts: 64
Location: England
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| Posted: Thu May 31, 2007 12:53 am |
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Thanks PCM Prorammer,
It's always something simple...  Though I've not tried it, it makes perfect sence. 
Cheers Scott |
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