Description:

This driver controls a Dwin HD-700 (or HD-500) CRT Front Projection unit. The Dwin HD-700/500 are very popular projectors, due to their small size and weight (65lbs), high light output, complete silence, and reasonable price (reasonable being a relative term of course.) It is a 7" CRT projector, with a real world resolution somewhere around the 1280x720 range on a 16:9 screen. Unlike many projectors these are very, very quiet, effectively silent, which is important when it is hanging right over your head.

This driver just happens to have a client side driver, though it doesn't require any configuration. Here is a screen shot of the interface:

Like many projectors, there isn't a lot of need for interaction with the Dwin on a daily basis. The driver allows you to power the projector on and off, and select from the available sources. The list of sources that are legal for the current input format (whose attributes are shown in the lower right), are shown in the list box. The currently highlighted entry is the active one.

Quirks and Limitations:

The Dwin has two concepts of 'power'. There is a hardware power button, which will completely power it down, but in almost all cases that would be left on all the time, and the 'soft' power setting used to control the projector. The soft power mode will put the projector into a kind of hibernation mode, but it will still respond to the control port (and can optionally be set to power on automatically upon sensing an input signal.) In this mode, you can power up the projector via CQC, which is definitely the desired mode.

The Dwin communications protocol is not very good. Its difficult to write a really high quality driver for it, because it has long periods (5 seconds or more) where it will just not respond to the communications port. For instance, when it is first soft powered on or off, or when it sees a new signal type. Because of this, the driver must be very tolerant of these long delays without being fooled into thinking the Dwin has disappeared. Because of this, it tends to be a little slow.

It also means that, when you are writing macros, you must do things like turn it on, then wait to make sure its turned on before trying to send it another command. Or, if you cause your video switcher to send it a different signal, you'll either need to sleep for 4 or 5 seconds before attempting to select a projector memory (if you have more than one legal one for that signal type and want the macro to select a particular one), or you can wait until you see the new signal refresh rate if it is different.

The Dwin protocol does not really provide full access to the setup services of the projector. Beyond just the basic controls, provided by the client interface, it really just provides the ability to send 'cursor up', 'cursor down', 'digit 1', etc... types of commands, i.e. you can kind of drive the interface in a simple way but not really control it in a powerful way that allows you to really see the menus from the computer interface. So this driver does not really attempt to provide any projector configuration functionality.

Connection Details

The Dwin uses a serial connection. It requires a three wire 9-pin null modem serial cable (NOT a straight through cable!) The serial port parameters are fixed, so you are not given a chance to configure them, you just get to choose the serial port. The parameters are 9600 baud, 8 bits, one stop bit, no parity, no flow control.

The Dwin protocol is very simple and text based. So you can confirm your cable connection by using a terminal program (such as the HyperTerminal one that comes with Windows) to set up the serial port and then type

<S>

which should cause the Dwin to respond with a string of status data. Don't press enter, since the trailing > character is what triggers it to reply. If you turn on local echo, you can see better what you are typing. If this works, then you can be sure that any problems you have are not cable related.

Driver Fields

This section lists the fields that the driver makes available, their types, minimum and maximum values, etc...

Name	Type	R/W	Description/Limits
ActiveSource	String	R/W	The name of the active source. It is writeable to allow you to force selection of a particular source if more than one are available for a particular signal type.
Brightness	Card	R/W	The brightness value of the currently active source. It will be from 0 to 100.
Contrast	Card	R/W	The contrast value of the currently active source. It will be from 0 to 100.
Frequency	Float	R	The current horizontal scan frequency for the currently active source. It is a floating point value, since the scan frequencies aren't necessarily integral values.
Power	Boolean	R/W	This field indicates the power state. It is writeable to that you can power the projector on or off as needed.
Rate	Float	R	The frame rate for the currently active source, in frames per second.