Starlight Xpress Camera Hackers Page

New! Windows SDK info here.

The Starlight Xpress Cameras are great for the coder.  If you want to write drivers for the cameras themselves, or control the cameras for specialized tasks, this is the place.  Terry Platt has been the force behind these cameras and has always provided very generous support for those who wanted to write code for his cameras.  You can find links to his original source code on the Starlight Xpress site.

The USB interface that SX designed for the parallel port cameras was an ingenious way to improve the performance of the cameras while retaining the investment people had made in their cameras.  It also a most hackable interface.  It is based on the Anchor single chip USB interface with built-in 8051.  It works by showing up as a generic USB device.  A special driver for the generic device downloads code onto on-board RAM and resets the chip.  The device renumerates as another device which then has all the functionality of the downloaded code.  This makes code updates a simple matter of installing a new HEX file on the host PC.  The newer SXV cameras have a more advanced USB chip built right into the camera, but the concept is the same.

Getting the new HEX file

The new camera's code isn't publically available yet, but I've backported the functionality to the original USB interface and made it available under the GPL.  To build, you need a free 8051 compiler available at sdcc.sourceforge.net.  They have both *nix and Windows versions of the compiler available for download.  The two source files you need from here are the EZUSB header file and the main source file:

ezusb.h
sx_ezusb.c

Once the compiler is installed properly, build the hex file like such:

sdcc --stack-after-data sx_ezusb.c
Update:  the latest CVS version of the compiler doesn't require the stack-after-data flag.

This will create a universal HEX file with an uninitialized camera model.  You will need to tell the USB interface which camera is attached.  To do that, you need to know the programmers interface to the USB device.  The programmers reference is available here:

StarlightXpress USB Interface Programmers Reference

Universal HEX file for original USB interface.

SX_EZUSB.HEX

You can also build the HEX file with an initialized camera model by adding one of the following:

-D CAMERA_MODEL=0x45    /*  MX5 */
-D CAMERA_MODEL=0xC5    /*  MX5C */
-D CAMERA_MODEL=0x47    /*  MX7 */
-D CAMERA_MODEL=0xC7    /*  MX7C */
-D CAMERA_MODEL=0x49    /*  MX9 */
-D CAMERA_MODEL=0x05    /*  HX5 */
-D CAMERA_MODEL=0x09    /*  HX9 */

Or, you can download prebuilt versions below:

MX5.HEX
MX5C.HEX
MX7.HEX
MX7C.HEX
MX9.HEX
HX5.HEX
HX9.HEX

These HEX files need to be renamed 05472131.HEX and copied into the \WINDOWS\SYSTEM32\DRIVERS directory.  Beware!  These HEX files are not compatible with the HEX files on the SX website or downloaded with third party software.  When support for the new SXV cameras becomes available, you should be able to substitute this HEX file and have it show up as a compatible SXV camera.  Save your current HEX file!  You can always download the original HEX file or re-install your third party software to revert to original functionality.  You may need a more up-to-date USB driver, now named SXVIO.SYS in the SXV install.  Install it with this INF file.  If you have the SXV camera, you already have the correct HEX file for your camera but probably want the new SXVIO.SYS file anyway.

NEW!
Windows SDK

For connecting and using the cameras.  This SDK takes care of low-level intefacing to the SX USB and USB2 cameras.  It also manages the model setting of the original USB interface and saving it in the registry for future reference when using the universal HEX file.  You will need an updated SXVIO.SYS file installed with SXVIO.INF to work correctly with the SDK.  To simplify the interface to the camera, use the SX USB camera DLL, sxusbcam.dll.  In your code, include the sxusbcam.h file and link to sxusbcam.lib.  You can look at the source to sxusbcam.dll in sxusbcam.c.

I used the free Borland C++ compiler to build the DLL and sample programs.  The first program, sxusbparams.exe (sxusbparams.c), opens all the available cameras and prints out all the camera parameters and capabilites.  It is a console application.  If nothing is returned, no cameras were found.  If you have a camera plugged in and nothing was printed out, make sure the latest SXVIO.SYS was installed.  The second application is a little more fun.  Sxvideo.exe (sxvideo.c) treats your camera as a low-light level video camera similar to the AstroVid StellaCam.  Use the F1 through F10 keys to set the exposure on a semi-log scale.  The space bar cycles through the available palettes.  The README files gives more details.  I hope to port over the TDI (drift scanning) application from Linux, but I'm not sure if it will have an interactive mode like the Linux version.


OK, now for some fun...

Serial Port Hack

One thing that really bugs me is the tangle of cables required to hook all the devices up for imaging.  The USB interface chip has a built-in 8051 MCU which also has its own built-in serial ports.  On the new SXV camera it was easy to build the serial ports into the camera form the outset.  But the idea came from my hacking the original USB controller to give up one of its serial ports for device control.  Now I didn't want to add a lot of hardware and had limited resources.  The RS-232 interface spec sets the pin logic to use -12V for a 1 and +12V for a 0.  There was no way to easily add that kind of control to the existing controller, so I just used a 7404 hex inverter to use 0V for 1 and +5V for 0.  For simple devices, it actually works.  Here is the link for more info.

Drift scanning

Drift scanning, or Time Delay Integration, is a method for imaging large chunks of the sky with a fixed camera.  In essence, you align the camera's pixel rows with lines of right ascension.  The image on the CCD is clocked out at sidereal time, thus imaging the sky as it passes over the CCD.  You need to know the focal length of the camera/telescope and the declination it is pointing in order to calculate the sidereal readout rate.  Look in the samples directory for tdi.c.  This implements a basic drift scan program.  There is also tdi_cal.c which creates calibration frames for drift scanning.

Autoguiding

One feature of the new SXV cameras that I'm particularly fond of is the autoguider mode.  The SXV camera has built-in firmware that communicates through the serial port by default.  If the camera is powered up with a special patch cord, a handheld device like a PalmPilot can talk to the camera and autoguide.  I have written a PalmPilot app to do just this.  It is available under the GPL here.  The name it builds under is star_pilot, but there are already many apps named Star Pilot avaialable so the new name is SXV Pilot.  The build process just doesn't reflect the name change yet.  You can get the pre-built prc file here.