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g@rd3n3r
Joined: 14 Jul 2016
Posts: 2
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| can_putd |
 Posted: Tue Nov 14, 2017 2:56 pm |
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revisiting after a long haitus.
can_putd(int32 id, int * data, int len,int priority, int1 ext, int1 rtr);
question about priority. The lower the value the higher the priority the message will be, right? |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19518
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| Posted: Tue Nov 14, 2017 3:39 pm |
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No. The message with the _lowest_ priority is postponed in the event of a conflict.
Read the comments in the driver itself:
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// priority - priority of message. The higher the number, the
// sooner the CAN peripheral will send the message.
// Numbers 0 through 3 are valid.
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0 to 3 only. 3 is the highest priority, 0 the lowest.
This is standard on CAN itself. |
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newguy
Joined: 24 Jun 2004
Posts: 1908
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| Posted: Tue Nov 14, 2017 4:42 pm |
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As Ttelmah has said, this is an internal (to the CAN peripheral) priority which is used to determine which message (if more than one), gets routed to the TX circuitry when a transmit slot opens up on the CAN bus.
For things like J1939 and/or NMEA 2000, you're correct in that the priority there corresponds to the first 3 bits transmitted on the CAN bus, and in that instance, the number of dominant/recessive bits determines who "wins" if more than one device attempt to simultaneously transmit on the bus. |
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