For testing and debugging it is a good idea to make an interface for the PC. This interface should be able to act as master and as slave. The master part is clear, the slave part is needed in order to monitor the bus and display all commands for example. The schematic can be downloaded here.
It uses a MAX232 as a RS232-to-5V convertor, next to the transmit and receive line it also offers one output and one input to the PC. The input is for detecting the interrupt signal, the output is for disconnecting the PC from the bus if it is placed in “listen” mode when another master is active in the setup. Also here the RS485 bus is created using the MAX489 and two RJ45 connectors in order to be part of the daisy chained slaves. The jumpers for terminating the bus and to activate the pull-up on the interrupt line only needs to be placed if the PC is the active master, in “listen” mode both should be removed.
Also this board is now being produced at EuroCircuits.