Tools: added param_unpack.py

decode param.pck file

Tools/scripts/param_unpack.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python
+'''
+unpack a param.pck file from @PARAM/param.pck via mavlink FTP
+'''
+
+import struct, sys
+
+from argparse import ArgumentParser
+parser = ArgumentParser(description=__doc__)
+parser.add_argument("file", metavar="LOG")
+
+args = parser.parse_args()
+
+data = open(args.file,'rb').read()
+last_name = ""
+
+magic = 0x671b
+
+# header of 6 bytes
+magic2,num_params,total_params = struct.unpack("<HHH", data[0:6])
+if magic != magic2:
+    print("Bad magic 0x%x expected 0x%x" % (magic2, magic))
+    sys.exit(1)
+
+data = data[6:]
+
+# mapping of data type to type length and format
+data_types = {
+    1: (1, 'b'),
+    2: (2, 'h'),
+    3: (4, 'i'),
+    4: (4, 'f'),
+}
+
+
+# we discard leading pad bytes (zero) on all params
+# pad bytes are inserted to ensure that a value doesn't
+# cross a block boundary
+pad_byte = 0
+if sys.version_info.major < 3:
+    pad_byte = chr(0)
+
+count = 0
+
+while True:
+    # skip pad bytes
+    while len(data) > 0 and data[0] == pad_byte:
+        data = data[1:]
+
+    if len(data) == 0:
+        break
+
+    ptype, plen = struct.unpack("<BB", data[0:2])
+    flags = (ptype>>4) & 0x0F
+    ptype &= 0x0F
+
+    if not ptype in data_types:
+        raise Exception("bad type 0x%x" % ptype)
+
+    (type_len, type_format) = data_types[ptype]
+
+    name_len = ((plen>>4) & 0x0F) + 1
+    common_len = (plen & 0x0F)
+    name = last_name[0:common_len] + data[2:2+name_len].decode('utf-8')
+    vdata = data[2+name_len:2+name_len+type_len]
+    last_name = name
+    data = data[2+name_len+type_len:]
+    v, = struct.unpack("<" + type_format, vdata)
+    count += 1
+    print("%-16s %f" % (name, float(v)))
+
+if count != num_params or count > total_params:
+    print("Error: Got %u params expected %u/%u" % (count, num_params, total_params))
+    sys.exit(1)
+sys.exit(0)