St 4.Command.Codes
St 4.Command.Codes
Game Manuals · PDF
| Filename | st-4.command.codes_.pdf |
|---|---|
| Size | 0.02 MB |
| Subsection | St 4.Command.Codes |
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SBIG SANTA BARBARA INSTRUMENT G ROUP
Applications Note
Interfacing to the ST-4
This note describes the operation of the ST-4 from a remote control standpoint. First
of all some general points of interest about the camera are:
• The ST-4 camera consists of a 192 (h) by 165 (v) element CCD, with readout
electronics, an 8 bit A/D converter, and a microcomputer with image storage
buffers for two images (light and dark frames). Although the CCD has more
horizontal elements than vertical elements, the size of each pixel is such
that the overall CCD array has an aspect ratio of 1:1.
• The ST-4 can be run stand-alone as a star tracker, controlling the relays
associated with the telescope drive to keep a star positioned at a fixed
position in the CCD array.
• The ST-4 can be controlled remotely over a three-wire serial interface
(Transmit Data, Receive Data and Ground) at various baud rates. Upon
power-up the camera starts at 9600 baud and can be switched remotely to
higher or lower baud rates. In our software we commonly use 57.6K baud,
but 19.2K, 9600 and 1200 are also supported for installations with longer
runs between the ST-4 and the computer. To communicate with the camera
you need 8 bits of data, even parity, and 1 stop bit.
• Instructions are sent to the camera and data is received from the camera in
packets, with each packet containing a checksum. Instructions sent to the
ST-4 are acknowledged by the ST-4 in different ways depending on the type of
instruction sent.
• Each packet contains a single checksum byte at the end to allow detection of
corrupted packets. The checksum byte is the sum of all the byte values in
the packet, excluding the checksum itself. Since it is a single byte, the
checksum wraps around to 0 at 256. For users computing the checksum you
would want to use an unsigned char type or the least significant byte of an
unsigned int.
• The majority of the remote control of the camera is achieved by setting bits
or writing bytes to memory inside the ST-4. The ST-4 then interprets those
bits and bytes and acts accordingly.
• Image data and image data alone sent from the ST-4 to the remote computer
can be compressed if the remote computer enables data compression in the
ST-4. The image data is sent as compressed data only if the compressed data
is shorter than the uncompressed data would be.
• The ST-4 has a special half-frame mode where an image in the lower half of
the CCD (83 lines) can be transferred to the top half at a high speed
(avoiding streaking due to integrating while reading out) and then those 83
lines are digitized as a half-frame image.
With these items in mind, below is a description of the instructions you can send to
the camera. There are only…
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