If the signals on the oscilloscope are really the labeled ones, then you have a hardware echo. The wiring of the ISL41387 in the schematic diagram of the DK looks like that shouldn't be the case, the pins DEN and /RXEN are both connected to P9.14. But then there is RS_ON and RXEN. I would study the Datasheet of the ISL together with the schematic to find out which configuration allows RS485 without hardware echo. The ISL41387 has a lot of possible configurations, including an internal loopback mode, even if A/B are not shorted to Y/Z it is possible to receive the sent data. www.intersil.com/.../isl81387-41387.pdf Edit: Internal loopback should be off since the RS_ON level is high, but if the A/B are shorted to Y/Z it seems that an external loopback is possible (for RS422). Setting switch 4 (Half) to "ON" should tie RXEN to GND, which should be the right configuration for RS485/half duplex. See Fig. 8 in the datasheet.
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