I'm working with a CAN bus based on CANOPEN protocol. My bus lenght is about 200m and the speed is 250Kb/s. I have 10 nodes on this bus, the master is at one end of the bus, on the other end I've got the resistance of 120 Ohm. The system works in a curious mode. Sometimes the master receives messages with RTR bit at 1, when it should be 0, for example in SDO messages, and sometimes not. Even if I reduce the speed at 125, the same thing happens! So, I don't think is a speed problem. I made a test, and it works: if I put a resistance also on the second last node, I do not receive unexpected RTR bit at 1, and the bus works correctly from the first to the last node. Can somebody explain this to me?