CAN bus: minimum safe distance between nodes

For everything that doesn't fit into the other (sub-) forums

CAN bus: minimum safe distance between nodes

Postby FranciscoSan » Sun Jun 07, 2015 12:50 pm

CAN bus proper wiring connecting my AQ6 and ESC32 required some investigation. CAN is a bus collision sense (CSMA/CA) protocol. There are guidelines to maintain signal integrity on the bus. Maximum bus length vs speed is not a limitation on multi-rotors. Minimum distance between adjacent nodes could be in some cases a parameter to consider.
Technical details can be found in several documents. (http://www.ti.com/general/docs/lit/getl ... er=slla279 ) Bus error likelihood increases with speed, number of nodes and uneven spacing:
-AQ is operating at/near maximum CAN bus speed (1Mbps)
-More than 10 CAN nodes onboard are realistic for some multi-rotors (AQ, 8x ESC32, OSD, gimbal controller, sensors, custom nodes –autonomous navigation, advanced sensor processing…)
-CAN wiring is custom (not tested)
To minimize error probability, following the guidelines, I wired using FTP cat5e cable, leaving 0.4m between adjacent CAN nodes and stubs below 0.1m. FTP shield connected to GND only on AQ side and bus termination on one bus end since DIMU includes a termination.
CAN is robust and takes care of errors. Errors appear only in extreme situations and are unlikely but cannot be excluded 100%. These errors are difficult to replicate and may or may not affect the operation of the multi-rotor. Since an aircraft I prefer to be on the safer side.
FranciscoSan
 
Posts: 1
Joined: Wed Jun 03, 2015 10:05 pm

Return to General Discussion

Who is online

Users browsing this forum: No registered users and 9 guests

cron