Technical Specifications

Technical Specifications

HomeWorks Interactive processors require the use of a standard 9-pin DB9 serial cable for communications with external equipment. This cable must be a 9-wire, straight through cable, not a 3-wire cable.

The available baud rates are 9600, 19200, 38400, 57600, and 115,200 baud. When dip switch #1 on S2 is up the baud rate is 9600 baud, and when it is down the baud rate is set to the user setting according to the SETBAUD command

The HomeWorks Interactive processors use hardware handshaking for flow control by default. Software handshaking will not work. The hardware handshaking may be disabled using the SETHAND command. If hardware handshaking is disabled, Lutron recommends using a low baud rate to avoid buffer overflow problems.

Other communication settings include, 8 data bits, 1 stop bit, and no parity bit

HWI Pin Number	HWI Pin Name	Description for HWI Processor	Required for Hardware Handshaking	Required for Simple Communications (hardware handshaking disabled)
1	DCD	Data Carrier Detect (input)
2	TX	Transmit Data (output)	X	X
3	RX	Receive Data (input)	X	X
4	DSR	Data Set Ready (input)	X
5	GND	Ground	X	X
6	DTR	Data Terminal Ready (output)	X
7	CTS	Clear To Send (input)	X
8	RTS	Request To Send (output)	X
9	RI	Ring Indicate (input)

General Specifications

The HWI processor connects to the serial port on a laptop using a standard DB-9 serial cable (all pins straight through)
The default configuration for the HWI processor is to use hardware handshaking, which requires the pin connections as shown in the table above. The SETHAND command can be used to disable hardware handshaking if needed.
When hardware handshaking is used, communications with the HWI processor will be reliable up to 115200 bps. (Note: Some older laptops cannot communicate reliably at 115200 bps)
The DTR output from the HWI processor is used by the HWI programming software. It indicates to the software that the processor is powered and ready for communications. This line is optional, and the DTR check can be disabled in the HWI programming software. Contact Lutron for more information.
The DSR input to the HWI processor is used to determine if an external device is controlling the handshaking lines. The DSR line must be asserted for the hardware handshaking to work properly. If the DSR line is unasserted while hardware handshaking is enabled, the processor will ignore the CTS input and always transmit characters.
All communications lines indicated in the Hardware Handshaking column are required when connecting a modem to an HWI processor.

Using Simple 3-Wire Communications

If hardware handshaking communications lines are not available on the external serial device, it is possible to communicate to the HWI processor using a simple 3-wire interface. The pins required are shown in the table above.
The hardware handshaking should be disabled on the processor using the SETHAND command.
In this configuration, the HWI processor will be unable to tell the external equipment to stop sending data, and the external equipment will be unable to tell the HWI processor to stop sending data. This can result in buffer overruns if the communications rates are too high.
Care must be taken to understand the amount of data being sent to/from the HWI processor using the 3-wire interface. Unnecessary monitoring messages should be disabled on the HWI processor to minimize communications.
Lutron does not recommend using the simple 3-wire interface to connect to external equipment that may send continuous data at a high data rate, or if your external equipment cannot process a continuous stream of monitoring output from the HWI processor.
The 3-wire interface cannot be used to connect a modem to an HWI processor.