This DIP switch setup is compatible with the USB-to-serial CH340 adapter and can be used as a quick reference when setting up your Roland DXY machine.
DXY-1200 RS232 Wiring
Preferred CH340 USB-RS232 wiring: use the full hardware-handshake cable shown in the diagram. This lets the plotter control host transmission during large HPGL transfers.
DB25 pin 2 -> DB9 pin 2DXY TXD output to host RXD
DB25 pin 3 -> DB9 pin 3DXY RXD input from host TXD
DB25 pin 4 -> DB9 pin 4DXY RTS output to host DTR
DB25 pin 5 -> DB9 pin 6DXY CTS input from host DSR
DB25 pin 6 -> DB9 pin 7DXY DSR input from host RTS
DB25 pin 7 -> DB9 pin 5Ground reference, required
DB25 pin 20 -> DB9 pin 8DXY DTR output to host CTS
Most important handshake line: DB25 pin 20 DTR to DB9 pin 8 CTS lets the DXY-1200 slow or stop the host when its receive buffer is filling.
DXY-1200 DB25 Pin Functions
Pin 2TXD, plotter output to host RX
Pin 3RXD, plotter input from host TX
Pin 4RTS output, always ON at about +12V
Pin 5CTS input to plotter
Pin 6DSR input to plotter
Pin 7SG signal ground
Pin 20DTR output from plotter
Minimum 3-wire connection: DXY pin 2 to host RX, pin 3 to host TX, and pin 7 to host GND.
TX/RX must be crossed: DXY pin 2 is the plotter's TXD output, so it must go to the adapter RXD. DXY pin 3 is the plotter's RXD input, so it must go to the adapter TXD. This cannot be swapped in software.
CTS and DSR can be left unconnected for normal use. The Roland manual states the plotter behaves as if CTS and DSR are ON when those inputs are unconnected. In the app, choose No-CTS paced sending when using a 3-wire cable.
DB9 reference: pin 2 RXD, pin 3 TXD, pin 5 GND, pin 7 RTS, pin 8 CTS.
Do not use pins 14 S.TXD or 16 S.RXD for normal serial communication; these are for Y-connection use.
DB25 numbering at the plotter connector: top row left to right is 13 to 1; bottom row left to right is 25 to 14.