Starlight Xpress SXV-AO unit - Manual (Page 11)

Handbook for the Starlight Xpress AO unit
Issue 1 21/8/2005
(hit limit)
G W 0 0 0 0 1 AO 1 step West G or L
(hit limit)
M N 0 0 0 0 1 Mount 1 step N M
M S 0 0 0 0 1 Mount 1 step S M
M T 0 0 0 0 1 Mount 1 step E M
M W 0 0 0 0 1 Mount 1 step W M
R Centre at low
speed (unjam)
K
L Get Limit switch
status
Character
with an ASCII
value between
0x30 and
0x3F
V Code version
number
V + 3 digits
X Handshake Y
U Update firmware U = Success,
Z = Fail
Parallel mode - the pulse width input specification
In pulse width mode, the input is a pulse width encoded signal with four direction lines
and a common ground, similar to that used for telescope mount control. However, the
pulse width per motor step is greatly reduced, so as to minimise the response time. The
minimum control pulse width is 10mS, which steps by 1 step in the appropriate direction.
Longer pulses follow in a linear progression, increasing by 1 motor step for each 10mS
incremental increase in pulse length. Note that only ONE input can be low at any one
time, otherwise other control functions may be inadvertently initiated.
Various different functions can be triggered by ‘abnormal’ input pulse patterns. The most
useful of these is the ‘centre’ mode, which should be used before beginning any guiding
sequence. In this, the inputs are all taken low and then simultaneously released. The AO
unit will then rapidly cycle between its limit switches and adjust the window to be
centred in the dynamic range and normal to the incoming light. Other functions include
the transmission of commands through the AO system to the mount (for ‘bumping’ the
mount position) and various setup modes, mostly used for calibration during assembly.
Please note that mount commands in serial mode can take place while further AO
commands are being received and acted upon. This allows the AO unit to follow the
mount correction and ‘back off’ the AO error without trailing the image. This is not
available in parallel mode at the present time, but may be added later. Be careful not to
send multiple commands without allowing time for the previous one to complete.