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CAN TRANSCIEVER ISO1050 Recieve issue

Sneha Thakur
Expert 2660 points
Other Parts Discussed in Thread: ISO1050EVM, ISO1050

Hi

I have been working with CAN in F28335 and CAN transciever ISO1050EVM.I am facing certain issues with the CAN communication..

The present status is that I can transmit but can not receive the acknowledgement from receiver.The connections are as follows:

TXD pin of ISO is the input to the board.

1. ISO1050 (1) is the circuit created by me similar to texas ISO1050 EVM with the difference that it does not have the 60 ohm terminating resistor.

2. ISO1050 (2) is texas EVM board with 60 ohm terminating resistor.

3.Running the CAN program and transmitting the data from DSP1 to DSP2.following program runs succesfully.

cantx.txt

initialization.txt

loopcount increments,CANES = 00080001 i.e. ACKE is set = The CAN module received no acknowledge. and also TM bit is set = The CAN module is transmitting a message.

TXd waveform on iso1050 (1) is similar to RXD waveform on iso1050 (2).

4. Now when I try to run the same program from DSP2 to DSP1 (i.e the same program in reverse direction,as CAN is bidirectional ) with texas ISO1050 (2) with 60 ohm terminating resistance transmission does not happen.Loopcount increments but CANES is set in which some or the error bits are set,there is no pulse observed on CANTX of DSP2 similar to DSP1 nor on Txd pin.

5. even though the connections are same,why isn't the transmission happeneing when a CAN transciever with 60 ohm terminating resistor comes first into the loop.

6.I guess once this works bidirectionally  my reciever would work fine too.

7.As the code works fine in one direction with the given hardware,it eliminates issues with code or with hardware.So is the problem with ISO1050 (2).To eliminate this possibility I created one more board simlar to EVM with 60 ohm terminating resistor and checking waveforms at each and every point.But the problem remains the same.

I can only come to conclusion that with EVM ,with 60 ohm terminating resistor the code needs to be changed or there is a problem with attaching the 60 ohm resistor......

I am actually confused.

thanks 

Sneha

Thanks

Sneha

  • 0
    Guru 27285 points
    Hi A fundamental test seems to be missing, what happen if program loaded on 1 and 2 get exchanged? transmission still fail 2 to 1 or reverse direction of fault?
    This to see if software is ok and initialization of ECAN too, if this reverse, then is software issue else you need try if defect can be ISO or some possible trouble in processor soldering or in the worst case port damaged.
  • 0 in reply to Roberto Romano
    Expert 2660 points

    Hi Roberto

    The transmission fails from 2 to1 in reverse and also if the program is exchanged.It doesnt even execute the transmission program of 1 to 2 which was successfully running in direction 1 to 2.

    So the problem particularly arises only when this ISO module having TXD resistor comes into picture.To elimiate any hardware issue I myself came up with the transciever  and it worked successfully in either direction after removal of this 50 ohm resistor in between TXD and GND1.

    Thanks

    Sneha

  • 0 in reply to Sneha Thakur
    Guru 27285 points

    On your description terminating was specified @60Ohm and 60 Ohm is the parallel resistance on CANBUS.
    50 Ohm standard terminating resistor on dev kit are there to do measurement with instrumentation and reduce cable ringing. When you attach them to a processor or another digital device they must be removed, this case you feed signal from pin not SMA connectors.

     About 60Ohm resistor, till you are testing very short connection one parallel load can be ok, when you use a real bus also 60Ohm has to be removed and TWO and ONLY TWO resistor @120Ohm need be placed at both end of transmission line. (both end of transmission cable)