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Active20 days ago
I am trying to establish a two-way communication via Python3. There is a laser range finder plugged into one of my USB ports and I'd like to send/receive commands to that. I have a sheet of commands which can be sent and what they would return, so this part is already there.
- Nov 16, 2016 Now, launch the program to read messages sent on the serial port from your device (for example an Arduino). Sudo python readserial.py Reading the messages of a Gateway MySensors on the serial port of a Raspberry Pi.
- The Adafruit IO Python library will export the UART device tree overlays as a convenience. There are five serial ports brought to the expansion headers (UART3 only has a single direction, TX), and one (UART0) with dedicated headers that aren't available to use in your Python programs.
What I need is a convenient way to do it in real-time. So far I have the following code:
PySerial includes a small console based terminal program called serial.tools.miniterm. It ca be started with python-m serial.tools.miniterm (use option -h to get a listing of all options).
So in the above code I am sending '1' which should trigger 'getDistance()' function of the laser finder and return the distance in mm. I tried this on Putty and it works, returns distances up to 4 digits. However, when I launch the above Python script, my output is only the following:
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and it goes forever. There is no read data or whatsoever.
Where am I mistaken?
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3 Answers
Apparently much more simpler version of the code solved the issue.
Output, as desired:
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It seems to me that your
ser.timeout = None
may be causing a problem here. The first cycle of your while
loop seems to go through fine, but your program hangs when it tries ser.readline()
for the second time.There are a few ways to solve this. My preferred way would be to specify a non-
None
timeout, perhaps of one second. This would allow ser.readline()
to return a value even when the device does not send an endline character.Python Programming Serial Port
Another way would be to change your
ser.readline()
to be something like ser.read(ser.in_waiting)
or ser.read(ser.inWaiting())
in order to return all of the characters available in the buffer.Alton CampbellAlton Campbell
Reyhaneh TrbReyhaneh Trb
Python Serial Programming Pdf
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Active4 years, 7 months ago
I am sending serial data from a Raspberry Pi to an Arduino using a Python program. I am running Python 2.7.3. The program is:
The problem is that nothing seems to be sent by these three lines if they are run in a program. But if I run them line by line in a Python shell, they work fine.
Also, if I have the Arduino Serial Monitor open, the program works fine as well, without running the lines one by one in the shell.
EDITED TO ADD:
Pyserial
It seems that there is some delay in sending to the Arduino. So when I run the code in interpretive mode, it works, but if as a program, it doesn't. I think that because I tried the same program on a Windows machine.
If I run the program in interpretive mode, or even in debugging mode with a breakpoint on the ser.write command, it works. But not if run as a program.
EDITED TO ADD MORE:
It turns out that the Arduino has an auto-reset on serial communications that has to be disabled:
I used a 220 uF capacitor between the RESET pin and ground. That works.
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Tough to be bitten by a bug like that! It still smarts.
Daanii
DaaniiDaanii
Python Serial Read
1 Answer
Try this. If you can't run it under idle or etc, try terminal by typing python name.py. I also suggest you to check the data coming or written from/to Rpi with putty to be sure.
Python Import Serial
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