AnsweredAssumed Answered

k20 FLEXCAN example set to loopback, setup

Question asked by Robert Lewis on Oct 10, 2015
Latest reply on Oct 13, 2015 by Robert Lewis



I have been trying to get the flexcan example to run in loopback on our board without success. I have a 60 ohm resistor on each CAN-H and CAN-L pair and have tied CAN-H to CAN-L.


I looped the TCAN-H and CAN-L pins in order to follow the suggestion on this forum (twr-k20d72m and can) to allow the Tx line to toggle. I added a separate ISR for the Rx and Tx. What I need  to do is to check the HW functionality at this point using a single board and verify the signal levels.


I checked the init_gpio.c and we are using the default settings for the port pins PTA12 & PTA13 so no changes were needed. I didn't see any setting to enable the FLEXCAN modules in user_config.h. I can step through the init fcns for the CAN system and they do not return any error however I don't see any activity on the Tx line even when I set the code to loop transmitting the text string. I do get one single Tx interrupt but thats it.


So I am wondering if there is another setting somewhere I have missed. The k20dx256 is the same bsp as the k40dx256 so I used the example code for the k40.


I am trying to run this on MQX 4.01. Is loopback a reasonable mode to set the code to run in?


Can anyone tell me my error please. I can try the newer MQX 4.2 but would prefer to get this working under MQX 4.0.1 before expanding the project and potential problems.


Any advice would be appreciated.