Script to print new bitflips on CAN (#21294)

* Script to print new bitflips on CAN

* also print falling edges

selfdrive/debug/can_print_changes.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python3
+import binascii
+import sys
+from collections import defaultdict
+
+import cereal.messaging as messaging
+from common.realtime import sec_since_boot
+
+
+def can_printer(bus=0):
+  """Collects messages and prints when a new bit transition is observed.
+  This is very useful to find signals based on user triggered actions, such as blinkers and seatbelt.
+  Leave the script running until no new transitions are seen, then perform the action."""
+  logcan = messaging.sub_sock('can')
+
+  low_to_high = defaultdict(int)
+  high_to_low = defaultdict(int)
+
+  while 1:
+    can_recv = messaging.drain_sock(logcan, wait_for_one=True)
+    for x in can_recv:
+      for y in x.can:
+        if y.src == bus:
+          i = int.from_bytes(y.dat, byteorder='big')
+
+          l_h = low_to_high[y.address]
+          h_l = high_to_low[y.address]
+
+          change = None
+          if (i | l_h) != l_h:
+            low_to_high[y.address] = i | l_h
+            change = "+"
+
+          if (~i | h_l) != h_l:
+            high_to_low[y.address] = ~i | h_l
+            change = "-"
+
+          if change:
+            print(f"{sec_since_boot():.2f}\t{hex(y.address)} ({y.address})\t{change}{binascii.hexlify(y.dat)}")
+
+
+if __name__ == "__main__":
+  if len(sys.argv) > 1:
+    can_printer(int(sys.argv[1]))
+  else:
+    can_printer()