Develop Reference

read write communication pySerial

Hello I have trouble with read/write from or to device. I wanted to make a serial connection via rs 485 (half-duplex) . When I call read and write functions they didnt receive a data. Anyone know what I do wrong?
def Transmission(ser,data):
if ser.isOpen():
try:
print(data)
ser.flushInput()
ser.flushOutput()
ser.rtscts = True
ser.write(data)
time.sleep(0.1)
numOfLines = 0
print("write: " + data)
while True:
response = ser.readline()
print("read data: " + response)
ser.rtscts = False
numOfLines = numOfLines + 1
if(numOfLines >= 5):
ser.close()
except Exception, e1:
print "error communicating...: " + str(e1)
else:
print "cannot open serial port "
return response
Terminal didnt show receiving data:
powah
write: powah
read data:
read data:
read data:
read data:
read data:
I tried to write with read in the loop (with changing ser.rtscts). How to fix that problem? Thank You

Opening 2 serial ports simultaneously in python (one tx one for rx)

I am making a throughput test for a bluetooth link, and I need to send data through a serial port to one bluetooth device which will then transport that data wirelessly to another bluetooth device. The other device will then complete the circuit by sending the data back to the host PC via a different serial port.
The problem seems to be when I attempt to open up 2 different instances of PySerial, the program simply hangs. I have isolated it down to running vs. hanging when I comment out one of the two serial port instantiations. Anyone see a problem with how I'm doing this? If so, what is the proper way to do this? See code below:
#/usr/bin/python
import serial
import time
import sys
DEFAULT_BAUD = 115200
SEND_SIZE = 100
def addPath(file):
pth, fl = os.path.split(__file__)
return os.path.join(pth, file)
def is_number(s):
try:
int(s, 16)
return True
except:
return False
class SerialReader():
def __init__(self, portRx, portTx):
self.portTx = portTx
self.portRx = portRx
self.start_time__sec = time.time()
self.interval__sec = 0
self.buffer = []
self.sendtext = ''.join([str(i) for i in range(SEND_SIZE)])
# send first batch of data
self.portTx.write(self.sendtext)
def didDataArrive(self):
# Read port
self.buffer.extend(list(self.portRx.read(1024)))
# Step through the buffer byte and byte and see if the tick text
# is at the front.
while len(self.buffer) >= len(self.sendtext):
if self.buffer[:len(self.sendtext)] == self.sendtext:
# Discard the tick text
self.buffer = self.buffer[len(self.sendtext):]
# Record time
snapshot__sec = time.time()
self.interval__sec = snapshot__sec - self.start_time__sec
self.start_time__sec = snapshot__sec
# send more data
self.portTx.write(self.sendtext)
return True
else:
self.buffer.pop(0)
return False
def main(port1, port2, baudrate1 = DEFAULT_BAUD, baudrate2 = DEFAULT_BAUD):
try:
import serial
except:
traceback.print_exc()
print "="*60
print "You need to install PySerial"
print "Windows: easy_install pyserial"
print "Mac/Linux: sudo easy_install pyserial"
try:
s1 = serial.Serial(port1, baudrate1, timeout = 0.1)
s2 = serial.Serial(port2, baudrate2, timeout = 0.1)
print "Loading serial ports"
except:
print "Serial port error"
exit()
plot_stop = False
dataread = SerialReader(s2, s1)
try:
while plot_stop == False:
if dataread.didDataArrive():
print dataread.interval__sec
except KeyboardInterrupt:
print "Keyboard Interrupt"
plot_stop = True
finally:
print "Closing"
s1.close()
s2.close()
if __name__ == '__main__':
if (len(sys.argv) < 3):
print "Usage: python extract_data.py phonelink_serialport phonelinkclient_serialport [baudrate1] [baudrate2]"
else:
main(*sys.argv[1:])
If I remove one of the following lines (doesn't matter which one), the python script runs (although it eventually crashes because in the code it eventually tries to reference both ports). If I leave these lines in, the program seems to just hang (it just seems to sit there and run indefinitely):
s1 = serial.Serial(port1, baudrate1, timeout = 0.1)
s2 = serial.Serial(port2, baudrate2, timeout = 0.1)

Python Socket Connection Error/Exception Handling?

so I have the below loop that works great until it hits certain hosts that simply cause a connection error. Unfortunately, instead of skipping over these instances, it causes the script to crash. I know to catch and avoid this exception it is best to through the troubling statement (serveroutput = tn.read_until(b'STARTTLS')) in a try: except block. I can do that, however I am not sure how to catch the error and tell it to move on. If I add a break, it will break the loop and cause the script to stop prematurely anyway. How can I continue iterating through j? I've heard I can use 'continue' as a way to continue iteration, but am I even catching the right exception here?
My Code:
def getServers():
fp = open("mailserverdata.csv", "r")
pt = from_csv(fp)
fp.close()
domains = txt_domains.get(1.0, 'end').splitlines()
symbols = txt_symbols.get(1.0, 'end').splitlines()
for x in range(len(domains)):
#Start Get MX Record
answers = dns.resolver.query(str(domains[x]), 'MX')
#End Get MX Record
#Start Get Employees
if symbols[x]!='':
xml = urllib.request.urlopen('https://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.stocks%20where%20symbol%3D%22'+symbols[x]+'%22&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys')
dom = parse(xml)
numemployees = dom.getElementsByTagName('FullTimeEmployees')
if len(numemployees)!=0:
numemployees = numemployees[0].firstChild.nodeValue
else:
numemployees = 0
#End Get Employees
j=0
tlsbool = 'N'
verified = 'N'
for rdata in answers:
#Start Trim Domains
output = str(rdata.exchange)
output = output[:len(output)-1]
print(output)
#End Trim Domains
#Start Telnet
tn = telnetlib.Telnet(output,25)
tn.write(b'ehlo a.com\r\n')
serveroutput = tn.read_until(b'STARTTLS')
checkvar = "STARTTLS"
for checkvar in serveroutput:
tlsbool = 'Y'
break
#End Telnet
#Start verification
if output.find(domains[x])>-1:
verified = 'Y'
#End verification
if j==0:
pt.add_row([domains[x],output,tlsbool,numemployees,verified])
else:
pt.add_row(['',output,tlsbool,'',verified])
j = j + 1
txt_tableout.delete(1.0, 'end')
txt_tableout.insert('end',pt)
root.ptglobal = pt
Try Catch Code:
try:
serveroutput = tn.read_until(b'STARTTLS')
except SocketError as e:
if e.errno != errno.ECONNRESET:
raise # Not error we are looking for
pass # Handle error here.
Full Stack Error:
Traceback (most recent call last):
File "C:\Python34\lib\tkinter\__init__.py", line 1487, in __call__
return self.func(*args)
File "C:\Users\kylec\Desktop\Data Motion\Mail Server Finder\mailserverfinder.py", line 58, in getServers
serveroutput = tn.read_until(b'STARTTLS')
File "C:\Python34\lib\telnetlib.py", line 317, in read_until
self.fill_rawq()
File "C:\Python34\lib\telnetlib.py", line 526, in fill_rawq
buf = self.sock.recv(50)
ConnectionResetError: [WinError 10054] An existing connection was forcibly closed by the remote host
UPDATE:
I tried the following code but I received the following error.
Code:
try:
serveroutput = tn.read_until(b'STARTTLS')
except tn.ConnectionsResetError:
continue
Error:
AttributeError: 'Telnet' object has no attribute 'ConnectionsResetError'

What ended up working for me in the end was a modification of what #user3570335 had suggested.
try:
serveroutput = tn.read_until(b'STARTTLS')
except Exception as e:
tlsbool = '?'

Python checking for serial string in If statement

As a newbie to python, I'm trying to use it to read a file and write each line of the file to the RS-232 port. My code bellow seems to work for the most part, except for my listen and react segments. From poking around, it seems that my if statements can't read if I've received a "Start\r", or "End\r" string from my device (RS-232). Can anyone provide feedback on what is missing?
import serial
import time
port = "/dev/ttyS0"
speed = 9600
print("\n\n\n\nScript Starting\n\n\n")
ser = serial.Serial(port, speed, timeout=0)
ser.flushInput() #flush input buffer, discarding all its contents
ser.flushOutput()#flush output buffer, aborting current output and discard all that is in buffer
text_file = open("my.file", "r")
lines = text_file.read().split('\n')
i = 0
counter = 0
while i<len(lines):
response = ser.readline()
if (counter == 0):
print("\n\nProbing With Off Data\n")
ser.write('FFF')
ser.write('\r')
counter+=1
if (response == 'Start'):
ser.write('FFF')
ser.write('\r')
if (response == 'End'):
print("\nString Transmitted:")
print lines
make_list_a_string = ''.join(map(str, lines))
ser.write(make_list_a_string)
ser.write('\r')
print("\n")
i+=1
text_file.close()
exit(0)

Try using strip() to get rid of any trailing or preceding '\r's:
if (response.strip() == 'Start'):

How to read a string of integers received on python from serial arduino

I'm sending a list of values (e.g. 80,539,345,677) from Arduino to a Python app running on my RPi. I have not been successful in extracting the values and assigning them to respective variables or objects in the app.
Here's my code:
def read_values():
#if DEBUG:
print "reading arduino data"
ser = serial.Serial('/dev/ttyUSB0', 9600)
print "receiving arduino data"
ser_line = ser.readline()
print ser_line
ser.close()
ser_list = [int(x) for x in ser_line.split(',')]
ambientLight = ser_list[1]
print ambientLight
return ambientLight
What I'm getting from Python is:
reading arduino data
receiving arduino data
80,477,82,2
Traceback (most recent call last):
File "serialXivelyTest4c.py", line 77, in <module>
run()
File "serialXivelyTest4c.py", line 63, in run
ambientLight = read_values()
File "serialXivelyTest4c.py", line 27, in read_values
ser_list = [int(x) for x in ser_line.split(',')]
ValueError: invalid literal for int() with base 10: '8254\r80'
You can see that I'm getting values, but that they're being truncated. Can anyone please tell me where I'm going wrong here. Thanks so much.

I've never used an Arduino but here's how I read from serial with a different board. I used serial.
import streamUtils as su # see below
ser = su.connectPort("/dev/tty.SLAB_USBtoUART") # make sure you have the right port name
data = ""
while True:
try:
data = data + ser.read(1) # read one, blocking
time.sleep(1) # give it time to put more in waiting
n = ser.inWaiting() # look if there is more
if n:
data = data + ser.read(n) # get as much as possible
# I needed to save the data until I had complete
# output.
if data:
# make sure you have the whole line and format
else:
break
except serial.SerialException:
sys.stderr.write("Waiting for %s to be available" % (ser.name))
sys.exit(1)
sys.stderr.write("Closing port\n")
ser.close()
Here's the streamUtils.connectPort():
import serial
def connectPort(portname):
# connect to serial port
ser = serial.Serial()
ser.port = portname
ser.baudrate = 9600
ser.parity = serial.PARITY_NONE
ser.stopbits = serial.STOPBITS_ONE
ser.bytesize = serial.EIGHTBITS
ser.timeout = 15 # need some value for timeout so the read will end
try:
ser.open()
except serial.SerialException:
sys.stderr.write("Could not open serial port %s\n" % (ser.name))
sys.exit(1)
return (ser)