232直接转成全双工（4线制）485接口 只用一片MAX488即能转换成功，其实是422通信方式，已经测试通过。 带有配套电源电路-232 be transferred directly into a full-duplex (4 wire system) 485 with only a MAX488 that is able to convert successfully, in fact, is a 422 means of

RS485转RS232电路原理图及PCB图-RS232 RS485 switch PCB circuit diagram and map

232转485电路，电路从串口取电，无需外接电源-232 to 485 circuits, the circuit to take power from the serial port, no external power supply

232转485非常好的资料，有程序有电路图。-Very good information