here's the situation:
I have two stamps, one connected to port: /dev/ttyUSB1, and one external one, unconnected. The external one has a (Contiki based) program on it to send (every 2 seconds) a single letter across to the stamp that is plugged into the computer. stamp plugged into the computer has a program, also Contiki based, which reads this information via a radio signal.
Now, I have written a python program, making use of pyserial, which aims to read the information coming into the port and display it in terminal. I know the message is arriving correctly as I can print the message from the stamp connected via USB to terminal fine. But I am having trouble reading the information from the python code.
import serial, time, threading
ser = serial.Serial()
ser.port = "/dev/ttyUSB1"
ser.baudrate = 9600
ser.bytesize = serial.SEVENBITS
ser.parity = serial.PARITY_EVEN
ser.timeout = 0.1
ser.rtscts = 1
try:
ser.open()
except Exception, e:
print "error open serial port: " + str(e)
exit()
if ser.isOpen():
try:
numOfLines = 0
while True:
print ser.read()
numOfLines = numOfLines + 1
time.sleep(2)
if (numOfLines >= 50):
break
ser.close()
except Exception, e1:
print "error communicating...: " + str(e1)
else:
print "cannot open serial port "
When run, instead of printing the expected letter sent from the stamp every couple of seconds, it will print a few consistent, yet random letters. For example:
w
z
z
w
g
z
g
z
z
z
w
z
w
There is no output from the program when I remove the USB connected to the stamp. So it must be reading something from the port... Any help would be much appreciated.
It sounds like it could be a problem with the baudrate. you didn't post the code that does this:
ser = serial.Serial('/dev/ttyUSB1', timeout=1, baudrate=9600, rtscts=1)
Related
I am using 2 XBee pro S1, I want to read the packets received by the co-ordinator on my PC , it is enabled with API_2 and all other connections are done properly, I can see the packets with XCTU, I am using the python xbee library , but it gives no output :
The Code :
import serial.tools.list_ports
from xbee import XBee
import serial
ports = list(serial.tools.list_ports.comports())
for p in ports: #print the list of ports
print p
def toHex(s):
lst = []
for ch in s:
hv = hex(ord(ch)).replace('0x', '')
if len(hv) == 1:
hv = '0'+hv
hv = '0x' + hv
lst.append(hv)
def decodeReceivedFrame(data):
source_addr_long = toHex(data['source_addr_long'])
source_addr = toHex(data['source_addr'])
id = data['id']
samples = data['samples']
options = toHex(data['options'])
return [source_addr_long, source_addr, id, samples]
PORT = '/dev/ttyUSB0'
BAUD_RATE = 9600
ser = serial.Serial(PORT, BAUD_RATE)
print "Serial ports initialised...."
xbee = XBee(ser,escaped=True)
print "XBee object created"
while True:
try:
response = xbee.wait_read_frame()
sleep(0.5)
decodedData = decodeReceivedFrame(response)
print decodedData
print "data decoded"
except KeyboardInterrupt:
break
ser.close()
The port number and baudrate are connect, I change it to the appropriate portnumber every time I replug the coordinator to my PC.
My output looks like :
Serial ports initialised....
XBee object created
It stays like that and gives no output, even if I see the RX led blinking.
Below is the code written with only pyserial :
import serial
from time import sleep
port = '/dev/ttyUSB0'
baud = 9600
ser = serial.Serial(port, baud)
data = ""
while True:
try:
while ser.in_waiting:
sleep(1)
data = ser.read()
print data
except KeyboardInterrupt:
break
ser.close()
It gives the following output.
Could someone kindly help.
Are you sure you have the correct serial port and baud rate? Does the xbee package support API mode 2? It might only work with API mode 1.
Does that package have methods for accessing the raw byte stream instead of trying to read frames? Can you configure it to throw exceptions on parsing errors?
I would start with just printing response until you see that you're receiving data. And why include the sleep() call in that loop?
I'm not sure what you're trying to accomplish in toHex() but you might want to look at the Python method struct.unpack() or replace all of the work you do on hv with '0x%02X' % ord(ch).
#!/usr/bin/python
I am struggling with quite the simple problem. I want to read some data from the serial port first than start writing the data. The data reading and writing works well. The problem is I need to read first around 7 lines like
X7_SEM_V3_6
ICAP OK
SA OK
IC OK
RBDK OK
status OK
S OK
Then send 'I' followed by N and C, then 9 hex digits from the text file. The code below read one line and went into the writing section and read the whole text file;
X7_SEM_V3_6
000062240
000062241
ICAP
000062240
000062241
so on
after doing this to all seven read lines than it send I. I want it read all seven lines once than send I and start working. this is in while loop. If I use something else it just read first line and stuck. Please some one help.
import serial, time
import binascii
ser = serial.Serial()
ser.port = "/dev/ttyUSB1"
ser.baudrate = 38400
ser.bytesize = serial.EIGHTBITS
ser.parity = serial.PARITY_NONE
ser.stopbits = serial.STOPBITS_ONE
ser.xonxoff = False
ser.rtscts = False
ser.dsrdtr = False
number_address = 1341602
number_char = 9
timeout=1
f=open('lut.txt','r')
try:
ser.open()
except Exception, e:
print "error open serial port: " + str(e)
exit()
if ser.isOpen():
try:
ser.flushInput()
ser.flushOutput()
# reading
max_packet = 20
lines = 0
while True:
byteData = ser.read_until('\r',max_packet)
newdata=str(byteData)
print newdata.strip()
#ser.write('I')
ser.write('I')
time.sleep(0.01)
for line in f.readlines():
print line
ser.write('N')
time.sleep(0.01)
ser.write(' ')
time.sleep(0.01)
ser.write('C')
time.sleep(0.01)
for i in line:
newdata=i
ser.write(newdata)
time.sleep(0.01)
except Exception, e1:
print "error communicating...: " + str(e1)
else:
print "cannot open serial port "
I am trying to the first time to send and receive information through serial port. The manual for the device with which I am trying to talk can be found here. I am trying for a start to send a set of hexadecimals to ask about the condition of the system and my purpose is to ask in real time about the temperature and store it. Until now my code is this:
import serial
import time
#import serial.tools.list_ports
#ports = list(serial.tools.list_ports.comports())
#for p in ports:
# print p
ser = serial.Serial(port= '/dev/ttyUSB0',
baudrate=9600,
parity=serial.PARITY_EVEN,
stopbits=serial.STOPBITS_ONE,
bytesize=serial.EIGHTBITS, timeout=0, xonxoff=1, rtscts=1, dsrdtr=1)
command = "\x10\xFF\x29\x2C\x16"
command = command.decode("hex")
ser.write(command)
print command
#time.sleep(10)
ReceivedData = "\n nothing"
while ser.inWaiting() > 0:
ReceivedData = ser.read()
print ReceivedData
The problem is that I cannot get any response.
EDIT:
So I solved the communication problem. It turned out I was using an extension cable so the T and R channels were not correctly connected. Now The response that I receive is "\x00\x10\xFF\x29\x2C\x16" which is the same that I put in only with a \x00 in the front. Does this mean it is an error message? How do I calculate the 4th bit? Until now I am using an example from the manual.
dont use command = command.decode("hex")
just
command = "\x10\xFF\x29\x2C\x16"
ser.write(command)
should work i am sure it expects bytes like this
to put it differently
START_BYTE = "\x10"
ADDR_BYTE = "\xff"
FN_BYTE = "\x29"
CS_BYTE = "\x2C" # We assume you have calculated this right
END_BYTE = "\x16"
msg = START_BYTE+ADDR_BYTE+FN_BYTE+CS_BYTE+END_BYTE
ser.write(msg)
you can abstract this out since start and end and address are always the same
def send_fn(ser,FN_CMD):
START_BYTE = "\x10"
ADDR_BYTE = "\xff"
END_BYTE = "\x16"
CS_BYTE = chr((ord(ADDR_BYTE) + ord(FN_CMD))&0xFF)
msg = START_BYTE+ADDR_BYTE+FN_CMD+CS_BYTE+END_BYTE
ser.write(msg)
I have a task where I have to send keystrokes to a machine and to achieve the same I have two machine out of which one is Host Machine (running python scripts) and other is the target machine (where I have to send keystrokes). I am using "L3 Systems Inc's KeyAT device" on COM1.
Now the problem is I am unable to send keystrokes and following is the code I am running.
import serial, time
#initialization and open the port
#possible timeout values:
# 1. None: wait forever, block call
# 2. 0: non-blocking mode, return immediately
# 3. x, x is bigger than 0, float allowed, timeout block call
ser = serial.Serial()
#ser.port = "/dev/ttyUSB0"
ser.port = "COM1"
#ser.port = "/dev/ttyS2"
ser.baudrate = 9600
ser.bytesize = serial.EIGHTBITS #number of bits per bytes
ser.parity = serial.PARITY_NONE #set parity check: no parity
ser.stopbits = serial.STOPBITS_ONE #number of stop bits
#ser.timeout = None #block read
ser.timeout = 1 #non-block read
#ser.timeout = 2 #timeout block read
ser.xonxoff = False #disable software flow control
ser.rtscts = False #disable hardware (RTS/CTS) flow control
ser.dsrdtr = False #disable hardware (DSR/DTR) flow control
ser.writeTimeout = 2 #timeout for write
try:
ser.open()
except Exception, e:
print "error open serial port: " + str(e)
exit()
if ser.isOpen():
try:
ser.flushInput() #flush input buffer, discarding all its contents
ser.flushOutput()#flush output buffer, aborting current output
#and discard all that is in buffer
#write data
# ser.write("AT+CSQ")
ser.write("~~~~~~~~~~\r")
ser.write("~:04\r")
# ser.write('\x03')
#print("write data: AT+CSQ")
time.sleep(0.5) #give the serial port sometime to receive the data
numOfLines = 0
while True:
response = ser.readline()
print("read data: " + response)
numOfLines = numOfLines + 1
if (numOfLines >= 5):
break
ser.close()
except Exception, e1:
print "error communicating...: " + str(e1)
else:
print "cannot open serial port "
Can anyone please help
Thanks,
Vipul
The only problem is the ser.readline() returns binary , you need transform it into string: str(response), so it will work perfectly!
I'm writing a code used to send order to an avr. I send several information but between each write, I have to wait for an answer (I have to wait for the robot to reach a point on the coordinate system). As I read in the documentation, readline() should at least read until the timeout but as soon as I send the first coordinate, the readline() automatically return :
SerialException: device reports readiness to read but returned no data (device disconnected?)
When I put a sleep() between each write() in the for loop, everything works fine. I tried to use inWaiting() but it still does not work. Here is an example of how I used it:
for i in chemin_python:
self.serieInstance.ecrire("goto\n" + str(float(i.x)) + '\n' + str(float(-i.y)) + '\n')
while self.serieInstance.inWaiting():
pass
lu = self.serieInstance.readline()
lu = lu.split("\r\n")[0]
reponse = self.serieInstance.file_attente.get(lu)
if reponse != "FIN_GOTO":
log.logger.debug("Erreur asservissement (goto) : " + reponse)
Here an snipet how to use serial in python
s.write(command);
st = ''
initTime = time.time()
while True:
st += s.readline()
if timeout and (time.time() - initTime > t) : return TIMEOUT
if st != ERROR: return OK
else: return ERROR
This method allows you to separately control the timeout for gathering all the data for each line, and a different timeout for waiting on additional lines.
def serial_com(self, cmd):
'''Serial communications: send a command; get a response'''
# open serial port
try:
serial_port = serial.Serial(com_port, baudrate=115200, timeout=1)
except serial.SerialException as e:
print("could not open serial port '{}': {}".format(com_port, e))
# write to serial port
cmd += '\r'
serial_port.write(cmd.encode('utf-8'))
# read response from serial port
lines = []
while True:
line = serial_port.readline()
lines.append(line.decode('utf-8').rstrip())
# wait for new data after each line
timeout = time.time() + 0.1
while not serial_port.inWaiting() and timeout > time.time():
pass
if not serial_port.inWaiting():
break
#close the serial port
serial_port.close()
return lines