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CCS/TMS320F28069: CCE error state in canbus

Shiranga Ariyasinghe
Expert 1145 points
Part Number: TMS320F28069
Other Parts Discussed in Thread: ISO1050

Tool/software: Code Composer Studio

Hi,

I am using tms320f28069 micro-controller with iso1050 for canbus communication in a emi noisy environment. It is working few seconds after loading the code in emi environment. But after a few seconds canbus communication was stopped. At that time CCE and BE error bits were set. How can I solve this issue. I am using external oscillator and I have used common mode choke and tvs diode for the ISO1050.

thank you

  • 0
    TI__Guru* 95315 points
    It is evident the node is going into a bus-off condition because of excessive number of error frames. You need to take care of both conducted and radiated noise. What kind of mitigation mechanisms are you using for radiated noise?

    Is the CAN communication able to work for any length of time without the presence of EMI?

    Have you scoped the bus, both with and without the presence of EMI?

    Is the bus terminated correctly? (refer to my app.note SPRA876 for more debugging tips)

    Are any other peripherals (or the chip itself) getting affected because of the noise? Or is it only the eCAN peripheral?
  • 0 in reply to Hareesh Janakiraman
    Expert 1145 points
    Hi Hareesh,

    It seems mostly effected by conducted noise. We have checked can bus with scope, and I will take image again and upload soon. We have seen that noise pulses on can bus are in same frequency as the high power motor controller we are using.

    We are using fully isolated canbus using iso1050 with a common mode choke and a tvs diode and we are using shielded twisted pair automotive grade wire. Other than that we haven used any mechanism to mitigate radiated noise. Are there any mechanism we can use to mitigate the radiated noise other than that?

    Our longest can bus wire length is around 2m.

    I will take scope readings again and upload.

    We have used two 120ohm termination resistors to two nodes. Those two nodes are mostly at the both ends of can bus . There are four nodes in our can bus up to now.

    Up to now we can only see this on canbus. Seems other peripherals are working without an issue for now.
  • 0 in reply to Shiranga Ariyasinghe
    TI__Guru* 95315 points
    It is good you have identified the source of the noise. Often, this is the biggest challenge. Since you know the frequency of interest, it should be relatively easy to come up with the filtering solution. Have you looked at the datasheet of the common-mode choke?

    Regarding shielding for radiated noise, it is very hard to come up with suggestions without looking at the setup, but there are good resources on the web.

    Does lowering the bit-rate help? Try a very low bit-rate like 50 or 25 kbps.
  • 0 in reply to Hareesh Janakiraman
    Expert 1145 points
    I think we will not be able to reduce the can bus speed. We are using 500kbs. We have to maintain that.
  • 0 in reply to Shiranga Ariyasinghe
    TI__Guru* 95315 points
    I suggested lowering the bit-rate merely as a debug aid, not as a permanent solution. I should have clarified that.