when i got the exception:ModbusInvalidResponseError, "Invalid CRC in response" , it can't execute

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What steps will reproduce the problem?
1.master = modbus_rtu.RtuMaster(seri)
2.
while(True):
    try:
        logger.info(master.execute(1, cst.READ_HOLDING_REGISTERS, 13, 1))
    except modbus_tk.modbus.ModbusError, e:
        logger.error("%s- Code=%d" % (e, e.get_exception_code()))
    except modbus_tk.modbus_rtu.ModbusInvalidResponseError, e:
        logger.error("ModbusInvalidResponseError: %s"%e)

3.
    when i got the exception:ModbusInvalidResponseError, it could not work
and has no reponse in the loop. in the console it displays: 
DEBUG   modbus.execute  Thread-1 -> 1-3-0-13-0-1-21-201

What is the expected output? 
A:ModbusInvalidResponseError, "Invalid CRC in response"

What do you see instead?
A:DEBUG modbus.execute  Thread-1 -> 1-3-0-13-0-1-21-201

What version of the product are you using? 
A:0.3.2

On what operating system?
A:windows xp sp3

Please provide any additional information below.
Forgive my poor English

Original issue reported on code.google.com by bcw...@gmail.com on 10 May 2010 at 5:34

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additional, i have run that code in a thread like this:
self.thread = threading.Thread(target=self.Run, args=(self.dct, self.dctname))
self.thread.setDaemon(1)
self.thread.start()
self.alive.set()

def Run(self, dct, dctname):
    while self.alive.isSet():
        master....

Original comment by bcw...@gmail.com on 10 May 2010 at 5:39

[GoogleCodeExporter]

Hello

I am not sure that I understand your problem.

Do you miss a modbus_tk.modbus_rtu.ModbusInvalidResponseError exception when the
slave returns an bad CRC?

Is it right?

Original comment by luc.jean@gmail.com on 10 May 2010 at 5:41

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i find a method to resolve this problem:
when catch this type of exception:
i try to do master.close(),
then it can work normaly

Original comment by bcw...@gmail.com on 10 May 2010 at 5:46

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So the problem was that you were not able to communicate anymore after a bad CRC
query. Right?

Normaly, the master should "flush" the buffer before sending a query so you 
shouldn't
have this problem. I 'll look at this pb.

However if you have a workaround that fix the pb, it's perfect.

Best 

Original comment by luc.jean@gmail.com on 10 May 2010 at 7:18

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when modbus_tk.modbus_rtu.ModbusInvalidResponseError exception raised, i try to 
use
master.close() to fix it.
unfortunately , it raised a new Exception like this:
Response length is invalid 0- Code=ModbusInvalidResponseError.
although I tried to use master.close() to make it work, it also return "Response
length is invalid 0- Code=ModbusInvalidResponseError" on the next loop every 
time.

this is my log:

2010-05-11 15:22:16,407 ERROR   main.Run    Thread-1    Invalid CRC in response-
Code=ModbusInvalidResponseError
2010-05-11 15:22:16,407 DEBUG   modbus.execute  Thread-1    -> 1-3-0-13-0-1-21-201
2010-05-11 15:22:18,421 DEBUG   modbus.execute  Thread-1    <-
2010-05-11 15:22:18,421 ERROR   main.Run    Thread-1    Response length is invalid 0-
Code=ModbusInvalidResponseError
2010-05-11 15:22:18,421 DEBUG   modbus.execute  Thread-1    -> 1-3-0-15-0-1-180-9
2010-05-11 15:22:20,436 DEBUG   modbus.execute  Thread-1    <-
2010-05-11 15:22:20,436 ERROR   main.Run    Thread-1    Response length is invalid 0-
Code=ModbusInvalidResponseError
2010-05-11 15:22:20,436 DEBUG   modbus.execute  Thread-1    -> 1-3-0-16-0-41-133-209

Original comment by bcw...@gmail.com on 11 May 2010 at 7:29

[GoogleCodeExporter]

It seems that you don't receive any answer at all. Maybe you should investigate 
why
the device doesn't answer. Maybe teh query is not Oh (wrong slave id?)

Have you set a timeout? master.set_timeout(1.0) set a 1 sec timeout. If no 
answer is
received before the to elapsed an exception should be raised. Maybe the 
Exception
name should be improved.

But getting an exception is not a problem, you should catch it.

Original comment by luc.jean@gmail.com on 11 May 2010 at 9:48

[GoogleCodeExporter]

I have set the timeout 3.0s, and catched it.
my code like this:

>>modbus code:

    master = modbus_rtu.RtuMaster(serial)
    master.set_timeout(3.0)
    master.set_verbose(True)
    while True:
            try:
                resp = self.master.execute(1, cst.READ_HOLDING_REGISTERS, 13, 1)
            except modbus_tk.modbus.ModbusError, e:
                logger.error("%s- Code=%d" % (e, e.get_exception_code()))
            except modbus_tk.modbus_rtu.ModbusInvalidResponseError, e:
                logger.error("%s- Code=ModbusInvalidResponseError" % (e))
                self.master.close()
            except:
                logger.debug("other")

Original comment by bcw...@gmail.com on 12 May 2010 at 12:37

[GoogleCodeExporter]

Hi Luc,

I have found another pb,

>>code:
    logger.info(master.execute(4, cst.READ_HOLDING_REGISTERS, 16, 
    expected_length = 38))

when the expected_length=38 it raise a exception like this:
   "modbus_tk.modbus.ModbusInvalidResponseError: Response address 3 is different from
request address 4 "

when the expected_length>=39 it raise a exception like this:
    "modbus_tk.modbus.ModbusInvalidResponseError: Invalid CRC in response"

Original comment by bcw...@gmail.com on 12 May 2010 at 1:33

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i think may be my device has some problem

Original comment by bcw...@gmail.com on 12 May 2010 at 1:35

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i use another tool to test my device , it work nice.
i think there are some thing wrong in pyserial.
when it read the serial port ,it can't read the whole respose byte.
so i got a bad CRC

Original comment by bcw...@gmail.com on 12 May 2010 at 5:29

[GoogleCodeExporter]

Have you tried to remove the expected length? it should calculate the right 
length
for you

Original comment by luc.jean@gmail.com on 21 May 2010 at 8:29

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Please try the expected_length and rev 110 where reopen of the port has been 
slightly
improved

Original comment by luc.jean@gmail.com on 26 May 2010 at 3:08

• Changed state: Accepted