Python serial fails to write - python-2.7

I am using Python 2.7 and serial v 2.6 to listen to a serial port. I can listen to the port just fine, but I cannot write to the port.
import serial
cp = 5
br = 9600
ser = serial.Serial(5,br)
a = ser.readline()
Using this, I can listen to the outcoming data stream. However, if I want to change the status of the instrument (e.g. set GPS to off) I would write a command:
ser.write('gps=off')
When I do this, I get "6L" returned and the gps stay on. However, if I connect via TeraTerm I can see the data stream in in real time. While the data streams in I can type gps=off followed by a return and suddenly my GPS is off. Why is my command in Python not working like TeraTerm?
UPDATE
If I instead do
a = ser.write('gps=on')
"a" is assigned value of 6. I also tried sending a "junk" command via
a = ser.write('lkjdflksdjflksdjf')
with "a" assigned a value of 17, so it seems to be assigning the length of the string to a, which does not make sense.

I think the problem was the ser.write commands were getting stuck in buffer (I am not sure of that, but that is my suspicion). When I checked the input buffer I found it to be full. After flushing it out I was able to write to the instrument.
import serial
ser = serial.Serial(5, 9600)
# the buffer immediately receives data, so ensure it is empty before writing command
while ser.inWaiting()>0:
ser.read(1)
# now issue command
ser.write('gps=off\r')
That works.

Related

Qt Serial Communication not sending all data

I am writing a Qt application for serial communication with a Qorvo MDEK-1001. All built-in serial commands I've had to use work fine except for one: aurs n k, where n and k are integers corresponding to the desired rate of data transmission (e.g. "aurs 1 1\r"). Write function is:
void MainWindow::serialWrite(const QByteArray &command)
{
if(mdek->isOpen())
{
mdek->write(command);
qDebug() << "Command: " << command;
//mdek->flush();
}
}
If I send the command "aurs 1 1\r". It doesn't actually get sent to the device until I send another command for some reason. So if I subsequently send the "quit" command to the device, the returned data from the device is: "aurs 1quit", which registers as an unknown command. Any assistance getting this command to send properly is appreciated.
I've tried a bunch of stuff (setting bytes to write as second parameter in write(), using QDataStream, appending individual hex bytes onto QByteArray and writing that), but nothing has worked. This is the first time I've had to use Qt's serial communication software so I've probably missed something obvious.
On Linux Manjaro (same thing happens on Windows 8.1)
Connection settings: 8 data bits, Baud: 115200, No Flow Control, No Parity, One Stop Bit

Serial Communication in Raspberry pi 3 B+

I want to communicate between Raspberry pi 3 B+ and GSM GPRS A6. I tried and I am unable to send data to GPRS Module from Raspberry pi.
Now, I know that GPIO serial port is disabled by default in newer Operating Systems (in my case Raspbian Stretch), so I have enabled it by adding following line in config.txt file,
enable_uart=1
Here's my Code:
import serial
import time
port = "/dev/ttyS0"
COMM = serial.Serial(port, baudrate=115200)
while(1):
COMM.write("AT\r")
print (COMM.read(5))
This command is supposed to return "OK", but it does not and nothing is printed. I am using python 2.7.
Some people suggested me to send data using this method,
COMM.write('AT' + '\r')
I tried but it didn't help.
There is no problem with my GPRS module. It works file with arduino.
So, what am I doing wrong here?
Thanks in advance!
,
First , be sure to enable the Serial.
sudo raspi-config -> Interfacing Option -> Serial
Second , sudo nano /boot/cmdline.txt
Delete "console=serial,115200"
And Then
sudo nano /boot/config.txt
Add the end
dtoverlay=pi3-disable-bt
core_freq=250
While you use : Serial(/dev/ttyAMA0,9600)
try sending:
import serial
port = "/dev/ttyS0"
comm = serial.Serial(port, baudrate=115200)
while True:
comm.write('AT' + '\n\r')
msg = comm.readline()
print(msg)

Pyserial/Eye-tracker: Reading from serial port whilst displaying stimuli

I am using Pyserial (+Python 2.7) to read in eye-tracking coordinates taken from an eye-tracker (CRS Live-Track set as serial port). Using the code below I am able to successfully start the tracker, read/save a line of coordinates, stop the tracker, and close. My problem is I need to continuously read in the coordinates whilst carrying out other tasks such as stimuli display. As it stands, I can't do anything whilst I'm reading in data ('trial1 = ser.readline'). I have to wait until I've read in the data before I continue. Is there a way to read in the data from the serial port continuously whilst I am displaying stimuli/collecting responses etc.?
I need to turn the tracker on, collect the data for the duration of the trial, and then tracker off.
import serial, time
ser = serial.Serial(
port='COM3',
baudrate=9600,
parity=serial.PARITY_ODD,
stopbits=serial.STOPBITS_TWO,
bytesize=serial.SEVENBITS,
)
x = ser.is_open #check port is open
if x:
print "port is open"
print "port name is: %s" %(ser.name) #check which port
ser.flushInput()
ser.flushOutput()
running = True
while running:
ser.write('$Raw\r') #start eye-tracker
trial1 = ser.readline() #read a line
###i need to do stuff here###
ser.write('$Stop\r') #stop eye-tracker
running = False
ser.flushInput()
ser.flushOutput()
print trial1 #print coordinates output
ser.close()
Cheers,
Steve
ioHub by Sol Simpson provides asynchronous device monitoring from within PsychoPy. i.e it operates on an entirely separate process so you don't have to pause while monitoring the port in the main PsychoPy thread.
Serial port documentation in ioHub seems scarce but there is a demo here: https://github.com/psychopy/psychopy/blob/master/psychopy/demos/coder/iohub/serial/customparser.py
Another option would be to try threads. You could put your eye tracker in one thread and the rest of your code in another. There is a stack overflow answer about multithreading (not using psychopy and eye trackers) from 2010. If you scroll down you will see that someone links to a blog post about an updated approach that they think is easier.

IPv6 destination options header

I'm working on a software-defined networking research project, and what I need is to make a simple UDP server that puts a data tag into the destination options field (IPv6) of the UDP packet. I was expecting to either the sendmsg() recvmsg() commands, or by using setsockopt() and getsockopt(). So, Python 2.7 doesn't have sendmsg() or recvmsg(), and while I can get setsockopt() to correctly load a tag into the packet (I see it in Wireshark), the getsockopt() command just returns a zero, even if the header is there.
#Python 2.7 client
#This code does put the dest opts header onto the packet correctly
#dst_header is a packed binary string (construction details irrelevant--
# it appears correctly formatted and parsed in Wireshark)
addr = ("::", 5000, 0, 0)
s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
s.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_DSTOPTS, dst_header)
s.sendto('This is my message ', addr)
#Python 2.7 server
addr = ("::", 5000, 0, 0)
s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
s.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_RECVDSTOPTS, 1)
s.bind(addr)
data, remote_address = s.recvfrom(MAX)
header_data = s.getsockopt(socket.IPPROTO_IPV6, socket.IPPROTO_DSTOPTS, 1024)
I also tried this in Python 3.4, which does have sendmsg() and recvmsg(), but I just get an error message of "OSError: [Errno 22]: Invalid argument", even though I'm passing it (apparently) correct types:
s.sendmsg(["This is my message"], (socket.IPPROTO_IPV6, socket.IPV6_DSTOPTS, dst_header), 0, addr) #dst_header is same string as for 2.7 version
It looks like 99% of the usage of sendmsg() and recvmsg() is for passing UNIX file descriptors, which isn't what I want to do. Anybody got any ideas? I thought this would be just a four or five line nothing-special program, but I'm stumped.
OK, I'm going to partially answer my own question here, on the off chance that a search engine will bring somebody here with the same issues as I had.
I got the Python 3.4 code working. The problem was not the header, it was the message body. Specifically, both the message body and the header options value fields must be bytes (or bytearray) objects, stored in an iterable container (here, a list). By passing it ["This is my message"] I was sending in a string, not a bytes object; Python let it go, but the OS couldn't cope with that.
You might say I was "byted" by the changes in the handling of strings in Python 3.X...

How to Run a Command on the Serially Connected Device in python

I Have Connected a Telepresence Device serially to my PC and it is connected successfully but i am not able to read or write the Data from the Device,Can Any Buddy Help me..
Here is my Python Script.I Need my script to Execute the command whatever i give in its command prompt.
import serial
ser = serial.Serial()
ser.braudrate = 115200
ser.port = "/dev/ttyUSB0"
ser.open()
print ser.name
if ser.isOpen():
print True
elif ser.isOpen():
print False
ser.readall()
print ser
ser.write("hello\n")
print ser
I'm having a similar problem right now, but, in your case, instead of using ser.write() I'd try using ser.writelines. If you are still looking for documentation try here.