Re: serial communication error for loop

[MRAB]

On 2018-03-14 00:23, Dhileepan Kumar wrote:


#!/usr/bin/python

import serial
import MySQLdb
while True:
#establish connection to MySQL. You'll have to change this for your database.
dbConn = MySQLdb.connect("localhost","root","1234","ifet") or die ("could 
not connect to database")
#open a cursor to the database
cursor = dbConn.cursor()

device = 'com3' #this will have to be changed to the serial port you 
are using
arduino = serial.Serial(device, 9600)


try:
  data = arduino.readline()  #read the data from the arduino
  if not data.strip():
   continue
  pieces = data.split("\t")  #split the data by the tab
  #Here we are going to insert the data into the Database
  try:
cursor.execute("INSERT INTO answer1 (voltage,current) VALUES 
(%s,%s)", (pieces[0],pieces[1]))
dbConn.commit() #commit the insert
cursor.close()  #close the cursor
  except MySQLdb.IntegrityError:
print "failed to insert data"
  finally:
cursor.close()  #close just incase it failed
except:
  print "Failed to get data from Arduino!"


it is my program.if do not use while true loop successfully run but can't get a 
continues data from arduino so i have decide to using while loop  but if using 
while loop shows some error


(project) C:\Users\DHILEEPAN\project\project>python mysql.py
Traceback (most recent call last):
   File "mysql.py", line 13, in 
 arduino = serial.Serial(device, 9600)
   File 
"C:\Users\DHILEEPAN\Envs\project\lib\site-packages\serial\serialwin32.py", line 
31, in __init_
 super(Serial, self).__init__(*args, **kwargs)
   File 
"C:\Users\DHILEEPAN\Envs\project\lib\site-packages\serial\serialutil.py", line 
240, in __init_
 self.open()
   File 
"C:\Users\DHILEEPAN\Envs\project\lib\site-packages\serial\serialwin32.py", line 
62, in open
 raise SerialException("could not open port {!r}: 
{!r}".format(self.portstr, ctypes.WinError()))
serial.serialutil.SerialException: could not open port 'com3': WindowsError(5, 
'Access is denied.')

please any one fix this

It cannot open the port the second time because the port is already open 
from the first time.


You have put too much inside the loop. It should be more like:
# open database and serial
while True:
# do read and insertion
# close database and serial

Even better, use the 'with' statement, which is neater:

with :
with :
while True:
# do read and insertion
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Re: serial communication error for loop

[Chris Angelico]

On Wed, Mar 14, 2018 at 11:23 AM, Dhileepan Kumar  wrote:
>
> #!/usr/bin/python
>
> import serial
> import MySQLdb
> while True:
> #establish connection to MySQL. You'll have to change this for your database.
> dbConn = MySQLdb.connect("localhost","root","1234","ifet") or die 
> ("could not connect to database")

Ah, you've come from Perl I see.

> #open a cursor to the database
> cursor = dbConn.cursor()
>
> device = 'com3' #this will have to be changed to the serial port you 
> are using
> arduino = serial.Serial(device, 9600)

You're opening the database AND the serial port every time you go
through the loop. Is that intentional?

> try:
>   data = arduino.readline()  #read the data from the arduino
>   if not data.strip():
>continue
>   pieces = data.split("\t")  #split the data by the tab
>   #Here we are going to insert the data into the Database
>   try:
> cursor.execute("INSERT INTO answer1 (voltage,current) VALUES 
> (%s,%s)", (pieces[0],pieces[1]))
> dbConn.commit() #commit the insert
> cursor.close()  #close the cursor
>   except MySQLdb.IntegrityError:
> print "failed to insert data"
>   finally:
> cursor.close()  #close just incase it failed
> except:
>   print "Failed to get data from Arduino!"

Ouch. Any exception, you just print out a generic message and move on?
You're blinding yourself. Let the exception get properly displayed. It
might help you.

> 
> it is my program.if do not use while true loop successfully run but can't get 
> a continues data from arduino so i have decide to using while loop  but if 
> using while loop shows some error
>
>
> (project) C:\Users\DHILEEPAN\project\project>python mysql.py
> Traceback (most recent call last):
>   File "mysql.py", line 13, in 
> arduino = serial.Serial(device, 9600)
>   File 
> "C:\Users\DHILEEPAN\Envs\project\lib\site-packages\serial\serialwin32.py", 
> line 31, in __init_
> super(Serial, self).__init__(*args, **kwargs)
>   File 
> "C:\Users\DHILEEPAN\Envs\project\lib\site-packages\serial\serialutil.py", 
> line 240, in __init_
> self.open()
>   File 
> "C:\Users\DHILEEPAN\Envs\project\lib\site-packages\serial\serialwin32.py", 
> line 62, in open
> raise SerialException("could not open port {!r}: 
> {!r}".format(self.portstr, ctypes.WinError()))
> serial.serialutil.SerialException: could not open port 'com3': 
> WindowsError(5, 'Access is denied.')
>
> please any one fix this
>

This looks like possibly the device is already in use. Try opening the
device _just once_, or if you have to reopen it every time through the
loop, make sure you close it.

ChrisA
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