CAMERA = "SARBD01-DSCR110"
GAP = "SARUN04-UPHS060"
SAMPLES = 20
TOLERANCE = 0.01
TIMEOUT = 10.0

#shared stream - make sure the camera is running on a screenpanel on the same console!
cam_server.start(CAMERA + "_sp1", True)

intensity = cam_server.stream.getChild("intensity")


gap = Channel(GAP + ":GAP_SP", alias = "gap")
readout = Channel(GAP + ":GAP")

av = create_averager(intensity, SAMPLES, interval = -1, name = None)

def before(position, scan):    
    caput(GAP + ":GO", 1)  
    start = time.time()  
    while abs(readout.read() - gap.read()) > TOLERANCE:        
        time.sleep(0.1)
        if time.time() - start > TIMEOUT:
            raise Exception ("Timeout waiting gap change")    

ret = lscan (gap, av, 17.5, 19.5, 40, latency=10.0, before_read=before)


#run("CPython/wrapper")
#xdata = ret.getPositions(0)
#ydata   =  ret.getReadable(0)   
#(fit_amplitude, fit_phase_deg, fit_offset, ph_crest, fit_x, fit_y) = hfitoff(ydata , xdata)
#print fit_amplitude, fit_phase_deg, fit_offset
#plt = get_plots()[0]
#if plt is not None:
#    plt.addSeries(LinePlotErrorSeries("fit"))
#    plt.getSeries(1).setData(fit_x, fit_y)
#    plt.getSeries(1).setPointsVisible(False)
#    plt.setLegendVisible(True)