[Dcm] Vehicle Diagnostic Communication Part 82 [Simulation 21]

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https://www.simulationroom999.com/blog/diagnostic-communication-en-back-issue/

Introduction.
Python code for simulating WriteDataByIdentifier
Python code explanation for simulation of WriteDataByIdentifier
Conclusion.

Introduction.

Explanation of the AUTOSAR-Dcm simulation.
In this article, we will explain the Python code for the simulation of WriteDataByIdentifier.

Python code for simulating WriteDataByIdentifier

In this article, the WriteDataByIdentifier service will be explained.
The Python code for testing is shown as follows.

import isotp
import logging
import time
import threading

from can.interfaces.vector import VectorBus

class ThreadedApp:
   def __init__(self):
      isotp_params = {
         'stmin' : 0, 
         'blocksize' : 4,
         'wftmax' : 0,
         'll_data_length' : 8,
         'tx_padding' : 0xCC,
         'rx_flowcontrol_timeout' : 1000,
         'rx_consecutive_frame_timeout' : 1000,
         'squash_stmin_requirement' : False,
         'can_fd' : False,
         'tx_data_min_length' : 8
      }
      self.exit_requested = False
      #self.bus = VectorBus(channel='0', bitrate=500000)
      self.bus = VectorBus(channel='0', bitrate=500000, fd=True)
      addr = isotp.Address(isotp.AddressingMode.NormalFixed_29bits, source_address=0xF1, target_address=0x10) 
      self.stack = isotp.CanStack(self.bus, address=addr, params=isotp_params, error_handler=self.my_error_handler)

   def start(self):
      self.exit_requested = False
      self.thread = threading.Thread(target = self.thread_task)
      self.thread.start()

   def stop(self):
      self.exit_requested = True
      if self.thread.isAlive():
         self.thread.join()
   
   def send(self, msg):
      self.stack.send(msg)
   
   def my_error_handler(self, error):
      logging.warning('IsoTp error happened : %s - %s' % (error.__class__.__name__, str(error)))

   def thread_task(self):
      while self.exit_requested == False:
         self.stack.process()                # Non-blocking
         #time.sleep(self.stack.sleep_time()) # Variable sleep time based on state machine state
         time.sleep(0.001) # Variable sleep time based on state machine state

   def shutdown(self):
      self.stop()
      self.bus.shutdown()

def sendrecv( app, msg ):
   
   if msg[0] == 0x00:
      tsleep = msg[1]*0x100+msg[2]
      tsleep = tsleep / 1000
      print("sleep : %f [ms]" % tsleep)
      time.sleep(tsleep)
   else:
      print("Send msg : %s" % (msg.hex()))
      app.send(msg)
      t1 = time.time()
      p2 = 1.0   # P2時間
      while time.time() - t1 < p2:
         if app.stack.available():
            payload = app.stack.recv()
            print("Recv msg : %s" % (payload.hex()))
            if payload[0] == 0x7F and payload[2] == 0x78:
               t1 = time.time()
               p2 = 5.0    # P2*時間
            else:
               break
         time.sleep(0.001)


if __name__ == '__main__':
   app = ThreadedApp()
   app.start()
   
   datas=[
      bytes([0x22, 0x56, 0x78]),
      bytes([0x2E, 0x56, 0x78, 0x11, 0x22, 0x33, 0x44]),
      bytes([0x10, 0x03]),
      bytes([0x22, 0x56, 0x78]),
      bytes([0x2E, 0x56, 0x78, 0x11, 0x22, 0x33, 0x44]),
      bytes([0x27, 0x13]),
      bytes([0x22, 0x56, 0x78]),
      bytes([0x27, 0x14, 0xDE, 0xAD, 0xBE, 0xEF]),
      bytes([0x2E, 0x56, 0x78, 0x11, 0x22, 0x33, 0x44]),
      bytes([0x22, 0x56, 0x78]),
      bytes([0x2E, 0x56, 0x78, 0x01, 0x02, 0x03, 0x04]),
      bytes([0x22, 0x56, 0x78]),
   ]
   
   #while True:
   for i in range(len(datas)):
      sendrecv(app, datas[i])

   print("Exiting")
   app.shutdown()

Python code explanation for simulation of WriteDataByIdentifier

This time, I changed the code a little to support NRC$78.
Basically, it times out in P2 hours, but when NRC$78 is received, it times out in P2* hours and resets the timeout time.

The flow of the message being thrown is as follows.

(1)Check the value of DID=5678
(2)Write to DID=5678
(3)Transit to extendDiagnosticSession
(4)Check the value of DID=5678 (confirm that it has not changed)
(5)Write to DID=5678
(6)Seed request
(7)Confirms value of DID=5678 (confirms that it has not changed)
(8)Key is sent
(9)Write to DID=5678
(10)Confirm value of DID=5678 (Confirm rewriting)
(11)Write to DID=5678
(12)Confirms the value of DID=5678 (confirms that it has been rewritten)

WriteDataByIdentifier is protected by session and security, so the main thing is to check that area.

ReadDataByIdentifier is the opposite of WriteDataByIdentifier, so it is read each time and checked to see if the value changes or not.

Conclusion.

I wrote Python code to simulate WriteDataByIdentifier.
WriteDataByIdentifier is often protected by session and security, so the main test is to test it.

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