Starlight Xpress SX Universal filter wheel - Manual (Page 5)

Handbook for the SX Universal Filter Wheel - Issue 1, May 2009
- 5 -
or
Zero = filters moving
Get Filter Total Current Filter number
or
Zero = filters moving Zero
NB: The ‘Get Filter Total’ command responds straight away with a “filters
moving” message. However there is a delay of several seconds before the
Total Filters data is available to the “Request Current Filter Number”
command. This is the time taken for the wheel to complete between one and
two complete rotations. During this period the Total Filters will be reported as
zero. When this command is completed filter 1 is automatically selected.
Serial Port Protocol:
The SX filter wheel implements a four-character format, which has just three
commands thus:
Notes: Checksum is 8 bit addition of Header + Command + Data
0xA5 is the hexadecimal number = decimal number 165
0x20 is the hexadecimal number = decimal number 32
Output Command / Data from PC
Description Header
(1)
Command
(2)
Data
(3)
Checksum
(4)
Select Filter 0xA5 1 0x20 4 = 1+2+3
Request Current
Filter 0xA5 2 0x20 4 = 1+2+3
Get Filter Total 0xA5 3 0x20 4 = 1+2+3
Input Data to PC
Description Header
(1)
Response
(2)
Data
(3)
Checksum
(4)
Select Filter 0xA5 0x81 New Filter
Number
4 = 1+2+3
Request Current
Filter 0xA5 0x82 Filter Number
+ 0x30
4 = 1+2+3
Get Filter Total 0xA5 0x83 Total Filters +
0x30
4 = 1+2+3
Examples, (all characters expressed in hexadecimal):
Select Filter Number 3:
PC -> Filter Wheel, 0xA5, 0x01, 0x03, 0xA9
Filter Wheel -> PC, 0xA5, 0x81, 0x03, 0x29
Request Current Filter (which is 2):
PC -> Filter Wheel, 0xA5, 0x02, 0x20, 0xC7
Filter Wheel -> PC, 0xA5, 0x82, 0x32, 0x59