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Unread 01-13-2012, 12:00 PM
dyanoshak dyanoshak is offline
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AKA: David Yanoshak
FRC #2158 (ausTIN CANs)
Team Role: Mentor
 
Join Date: Dec 2007
Rookie Year: 2007
Location: Austin, TX
Posts: 165
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New Jaguar firmware version 101

There is an update to the Jaguar firwmare now available on www.ti.com/jaguar.

It is highly recommended that any teams using CAN update their Jaguar firmware to version 101. The new firmware will improve the Jaguar's ability to recover from errors caused by loose or faulty CAN cables.

Before, these errors could cause the Jaguar to stop responding to commands until it was power-cycled. Now, the Jaguar can recover without a power-cycle.

The detailed explanation:

The updated firmware allows Jaguar to gracefully recover from states where it can no longer communicate on the CAN bus. The Jaguar's CAN controller, by design, will take itself off the CAN bus when it detects too many transmit errors. The idea behind this is the following: If the CAN controller knows it is sending out lots of bad packets, it intelligently removes itself from the bus to prevent the bus from being flooded with bad traffic.

Before the update, Jaguar would stay in this "bus-off" state until the entire controller is reset (after a power-cycle). This would be good if the cause of the error never went away... but since we have found that the biggest cause for bad traffic has been loose or improperly crimped (therefore unreliable) CAN cables, it is better for the overall system that the Jaguar gets back on the bus.

With the new update, the Jaguar will see CAN controller go bus-off, it will report a COMM Fault, it will clear the state, and then it will return to the bus.

Note: Even though the Jaguar will recover and go back on the bus, there is still could be a large amount of bad traffic. Theoretically, if the bad traffic is frequent enough, you will not be communicating effectively with the Jaguar anyway. Be sure to read the Jaguar documentation found on www.ti.com/jaguar for CAN cable techniques or purchase already made cables from some sources listed on these forums.

-David
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