Tools: start of script to help decode stm32 ICSR register

pbarker@bluebottle:~/rc/ardupilot(master)$ ./Tools/scripts/decode-ICSR.py 4196355
VECTACTIVE: 3  (Hard fault)
RESERVED1: 0
ROTOBASE: 1
VECTPENDING: 0
RESERVED2: 0
ISRPENDING: 1
RESERVED3: 0
PENDSTCLR: 0
PENDSVCLR: 0
PENDSVSET: 0
RESERVED4: 0
NMIPENDSET: 0
pbarker@bluebottle:~/rc/ardupilot(master)$

Tools/scripts/decode-ICSR.py

@@ -0,0 +1,87 @@
+#!/usr/bin/env python
+'''
+decode an stm32 ICSR register value
+'''
+
+import sys
+import optparse
+
+
+def num(s):
+    try:
+        return int(s)
+    except ValueError:
+        return int(s, 16)
+
+
+parser = optparse.OptionParser(__file__)
+
+opts, args = parser.parse_args()
+
+if len(args) == 0:
+    print(parser.usage)
+    sys.exit(0)
+
+ICSR = num(args[0])
+
+# https://www.st.com/content/ccc/resource/technical/document/programming_manual/6c/3a/cb/e7/e4/ea/44/9b/DM00046982.pdf/files/DM00046982.pdf/jcr:content/translations/en.DM00046982.pdf
+# page 255
+
+
+def decoder_m4_vectactive(value):
+    exceptions = {
+        0: "Thread mode",
+        1: "Reserved",
+        2: "NMI",
+        3: "Hard fault",
+        4: "Memory management fault",
+        5: "Bus fault",
+        6: "Usage fault",
+        7: "Reserved....",
+        10: "Reserved",
+        11: "SVCall",
+        12: "Reserved for Debug",
+        13: "Reserved",
+        14: "PendSV",
+        15: "SysTick",
+    }
+    if value in exceptions:
+        exception = "%s" % str(exceptions[value])
+    else:
+        exception = "IRQ%u" % (value - 16)
+
+    sys.stdout.write(" (%s)" % exception)
+
+
+M4_BITS = [
+    ("0-8", "VECTACTIVE", decoder_m4_vectactive),
+    ("9-10", "RESERVED1", None),
+    ("11", "ROTOBASE", None),
+    ("12-18", "VECTPENDING", None),
+    ("19-21", "RESERVED2", None),
+    ("22", "ISRPENDING", None),
+    ("23-24", "RESERVED3", None),
+    ("25", "PENDSTCLR", None),
+    ("27", "PENDSVCLR", None),
+    ("28", "PENDSVSET", None),
+    ("29-30", "RESERVED4", None),
+    ("31", "NMIPENDSET", None),
+]
+
+for bit in M4_BITS:
+    (bits, name, decoder) = bit
+    if "-" in bits:
+        (start_bit, stop_bit) = bits.split("-")
+        start_bit = int(start_bit)
+        stop_bit = int(stop_bit)
+    else:
+        start_bit = int(bits)
+        stop_bit = int(bits)
+    mask = 0
+    for i in range(start_bit, stop_bit+1):
+        mask |= (1 << i)
+    value = (ICSR & mask) >> start_bit
+    sys.stdout.write("%s: %u" % (name, value)),
+    if decoder is not None:
+        decoder(value)
+    print("")