import  ch.psi.pshell.epics.ChannelDouble as ChannelDouble
A1 = ChannelDouble("x",            "SARUN13-DBPM070:X-REF-FB")
A2 = ChannelDouble("y",            "SARUN13-DBPM070:Y-REF-FB")
camera_name  = "SARBD01-DSCR110"
cam_server.start(camera_name+"_sp1", True)    #True for shared pipeline 
wait_cam_server_message()
S1   = cam_server.stream.getChild("intensity")

A1.initialize()
A2.initialize()
S1.initialize()
A1_init = A1.read()
A2_init = A2.read()
A1i    = A1_init-0.1
A1f    = A1_init+0.1
A2i    = A2_init-0.1
A2f    = A2_init+0.1
nstep  = 11
lat    = 5.0
nav    = 10


def data_ok():
    return (mps_beam_ok.read() == 1)

#def before_sample(record, scan):    
#    while not data_ok():
#        time.sleep(1.0)

def after_sample(record, scan):    
    if not data_ok():       
        time.sleep(1.0)
        record.invalidate()    
        print "Invalidating record: " + str(record)
try:
    S1_averager = create_averager(S1, nav, 0.1)
    r = ascan((A1,A2), (S1_averager), (A1i,A2i), (A1f,A2f), (nstep,nstep), latency=lat, after_read = after_sample)
    Act1     = r.getPositions(0)
    S1mean   = [val.mean for val in r.getReadable(0)]
    S1rms    = [val.stdev for val in r.getReadable(0)]
finally:
    A1.write(A1_init)
    A1.close()
    S1.close()
    #S2.close()