--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/pygpibtoolkit/gpib_utils.py Mon Feb 25 18:38:27 2008 +0100
@@ -0,0 +1,128 @@
+#
+"""
+Several untity functions for GPIB data conversions
+"""
+import struct
+import re
+import numpy
+
+########################################
+# internal binary types decoders
+
+def decode_float(s):
+ """
+ Decode a Float from the HP binary representation.
+ """
+ if len(s) == 4:
+ i1, i2, e = struct.unpack('>hbb', s)
+ i2 = i2 * 2**(-23)
+ return (i1/32768. + i2)*2**e
+ else:
+ i1, i2, i3, i4, e = struct.unpack('>hhhbb', s)
+ if i2 < 0:
+ i2 = (i2+32768.)*2**(-15)
+ else:
+ i2 = i2*2**(-15)
+ if i3 < 0:
+ i3 = (i3+32768.)*2**(-30)
+ else:
+ i3 = i3*2**(-15)
+ i4 = i4 * 2**(-38)
+ return (i1+i2+i3+i4)*2**(e-15)
+
+def decode_string(s):
+ """
+ Decode a string from the HP binay representation.
+ """
+ nb = ord(s[0])
+ s = s[1:nb+2]
+ r = ""
+ # XXX why do we need to do this? It's not described in the manual...
+ for c in s:
+ r += chr(ord(c) & 0x7F)
+ return r
+
+###
+# Datavlock useful functions
+def format_datablock_header(header, head_struct, columns=80):
+ """
+ Pretty print a data block (trace, state or coord)
+ """
+ bool_re = re.compile(r'((?P<before>.*) )?(?P<flag>\w+/\w+)( (?P<after>.*))?')
+
+ todisp = []
+ for row in head_struct:
+ key = row[0]
+ typ = row[1]
+ if typ is None:
+ continue
+ val = header.get(key, "N/A")
+ if isinstance(val, basestring):
+ val = repr(val)
+ elif typ is bool and isinstance(val, typ):
+ m = bool_re.match(key)
+ if m:
+ d = m.groupdict()
+ key = ""
+ if d['before']:
+ key += d['before']
+ if d['after']:
+ key += d['after']
+ key = key.capitalize()
+ val = d['flag'].split('/')[not val]
+ else:
+ val = str(val)
+ else:
+ val = str(val)
+ todisp.append((key+":", val))
+ maxk = max([len(k) for k, v in todisp])
+ maxv = max([len(v) for k, v in todisp])
+ fmt = "%%-%ds %%-%ds"%(maxk, maxv)
+ w = maxk+maxv+4
+ ncols = columns/w
+ if ncols:
+ nrows = len(todisp)/ncols
+ else:
+ nrows = len(todisp)
+ res = ""
+ for i in range(nrows):
+ res += "| ".join([fmt%todisp[j*nrows+i] for j in range(ncols)]) + "\n"
+ return res
+
+def decode_datablock_header(data, header_struct, idx=0):
+ d = data
+ if d[idx:].startswith('#'):
+ # we have a preliminary header here...
+ typ = d[idx:idx+2]
+ assert typ == "#A"
+ idx += 2
+ totlen = struct.unpack('>h', d[idx:idx+2])[0]
+ idx += 2
+ tt=0
+ header = {}
+ for i, (nam, dtype, fmt, nbytes) in enumerate(header_struct):
+ if dtype is None:
+ idx += nbytes
+ continue
+ elif dtype == str:
+ val = decode_string(d[idx:])
+ else:
+ if fmt:
+ v = struct.unpack('>'+fmt, d[idx: idx+nbytes])[0]
+ if isinstance(dtype, dict):
+ val = dtype.get(int(v), "N/A")
+ else:
+ val = dtype(v)
+ else:
+ val = dtype(d[idx: idx+nbytes])
+ header[nam] = val
+ idx += nbytes
+ return header, idx
+
+def read_datablock_trace(data, idx, nelts):
+ assert len(data[idx:]) >= (nelts*4), "data[idx:] is too small (%s for %s)"%(len(data[idx:]), (nelts*4))
+ resu = []
+ for i in range(nelts):
+ resu.append(decode_float(data[idx: idx+4]))
+ idx += 4
+ return numpy.array(resu, dtype=float)