Improve sequence offset seeking

FofbTool/Operation.py

@@ -66,7 +66,16 @@ def align_ccn(node_tangopath, comlbpif=0):
         time.sleep(2+np.random.uniform())
         prx.ccnpack0_control=2 # latch it
         time.sleep(2)
-        N.append(prx.ccnpack0_latchedseq1-prx.ccnpack0_latchedseq2)
+
+        _N = prx.ccnpack0_latchedseq1-prx.ccnpack0_latchedseq2
+
+        # handle diff going from 17 bits to 16bits offset
+        if _N > 0x7FFF:
+            _N=_N-0x10000
+        if -_N > 0x8000:
+            _N=_N+0x10000
+
+        N.append(_N)
 
         logger.debug("seq ({}, {}, {})".format(prx.ccnpack0_latchedseq1, prx.ccnpack0_latchedseq2, N[-1]))
 
@@ -76,12 +85,6 @@ def align_ccn(node_tangopath, comlbpif=0):
     if N in (-1, 0, 1):
         logger.warning("Sequence offset measured = {}, something might be wrong".format(N))
 
-    # handle diff going from 17 bits to 16bits offset
-    if N > 0x7FFF:
-        N=N-0x10000
-    if -N > 0x8000:
-        N=N+0x10000
-
 
     logger.debug("Setting sequence offset to {}".format(N))
     prx["comlbp{}_seqoffset".format(comlbpif)]=N