Serial communication Tx/Rx

[boylesg]

I tried the following but I get a permission denied error in Python:

Code: Select all

import serial
port = serial.Serial("/dev/ttyAMA0", baudrate=115200, bytesize=8, parity='N', stopbits=1, timeout=3.0)

So how do you do this correctly.

I am a complete newbie to python by the way.

[DougieLawson]

Add your userid to the dialout group.
sudo usermod -G dialout $(whoami)

[boylesg]

Still get permission denied.

Do you need to restart the Pi or something for the change to take effect?

[joan]

Still get permission denied.

Do you need to restart the Pi or something for the change to take effect?

You need to log out and log back in for user permission changes to take effect.

If it doesn't work could you say what ls -l /dev/ttyAMA0 reports?

[bensimmo]

Is it not serial0 now, especially if using the Pi3?
Would the Bluetooth deny access to ttyAMA0 ?

Of course it could be the other Pi's?


I never had to alter any groups (but I am 'pi') to get serial working.

[boylesg]

Is it not serial0 now, especially if using the Pi3?
Would the Bluetooth deny access to ttyAMA0 ?

Of course it could be the other Pi's?


I never had to alter any groups (but I am 'pi') to get serial working.

Pi 2 B+ I think it is.

[boylesg]

Still get permission denied.

Do you need to restart the Pi or something for the change to take effect?

You need to log out and log back in for user permission changes to take effect.

If it doesn't work could you say what ls -l /dev/ttyAMA0 reports?

crw--w---- 1 root tty 204, 64 Jul 3 23:48 /dev/ttyAMA0

[boylesg]

sudo chown pi:pi /dev/ttyACM0

This did the trick.

[boylesg]

I have my arduino uno connected to my pi tx/rx pins on the pi and D5 and D6 on the uno.

I am using SoftwareSerial on the Uno. I seem to be getting a bit of garbage in ArduinIDE serial monitor. I am wondering if software serial on the UNO is a problem for the Pi - I was reading some where that software serial on the Pi is not possible because it is not a real time operating system.

All I want to do at this stage is write some text to the serial port in Python and then see that text in the ArduinoIDE serial monitor.

I am getting a serial write exception Errno 5 in python though.

But I am getting a rapsberry pi password request (as well as the garbage) in the arduino serial monitor.

WTF is going on here?

[DougieLawson]

sudo chown pi:pi /dev/ttyACM0

This did the trick.

That's an ugly temporary hack. Add user pi to the tty group or your program will break next time you reboot your RPi.

[boylesg]

sudo chown pi:pi /dev/ttyACM0

This did the trick.

That's an ugly temporary hack. Add user pi to the tty group or your program will break next time you reboot your RPi.

'sudo adduser pi dialout' does nothing to solve the problem in python.

The 'ugly hack' is the only thing that works at present.

[DougieLawson]

How about sudo adduser -G tty pi ? Or you've got to write a udev rule to change the ownership every time you reboot.

[boylesg]

How about sudo adduser -G tty pi ? Or you've got to write a udev rule to change the ownership every time you reboot.

Option g is ambiguous (gecos, gid, group)

[boylesg]

Why is this so bloody difficult???

Raspberry Pi Serial GPIO Configuration

0. if you have not seen my article on how to remote access your Raspberry Pi, take a look here:

https://oscarliang.com/setup-raspberry- ... te-access/

1. In order to use the Raspberry Pi’s serial port, we need to disable getty (the program that displays login screen) by find this line in file /etc/inittab

Found the above except there no such file as /etc/inittab on my pi.

So what do I do?

[boylesg]

Looks like this ttyAMA0 business is bogus.
It appears as though the serial port is tty1 because port = serial.Serial('/dev/tty1', baudrate=9600) works in python for me.
Found tty1 in /boot/cmdline.txt
You are supposed to remove console=tty1 from the line of text in that file which, as I understand it, should prevent the RPi from sending the login rubbish to my arduino.

Does that sound right?

I have been reading this: https://oscarliang.com/raspberry-pi-and ... rial-gpio/

[boylesg]

Ah ha!

Found this for disabling pi login over serial.

http://www.instructables.com/id/Read-an ... pberry-Pi/

[joan]

Are you using?

• the Pi's UART (/dev/ttyAMA0) which means you use pins 8/10 at the Pi or
• an Arduino to Pi USB dongle (/dev/ttyACM0) which means you use USB at the Pi end.

That makes a difference.

[gordon77]

I have my arduino uno connected to my pi tx/rx pins on the pi and D5 and D6 on the uno.

I am using SoftwareSerial on the Uno. I seem to be getting a bit of garbage in ArduinIDE serial monitor. I am wondering if software serial on the UNO is a problem for the Pi - I was reading some where that software serial on the Pi is not possible because it is not a real time operating system.

All I want to do at this stage is write some text to the serial port in Python and then see that text in the ArduinoIDE serial monitor.

I am getting a serial write exception Errno 5 in python though.

But I am getting a rapsberry pi password request (as well as the garbage) in the arduino serial monitor.

WTF is going on here?

Try...
Hcorr = 'test'
ser.write(bytes(Hcorr.encode('ascii')))

You may need to add some delay after opening the port for the uno to settle.

[boylesg]

Don't know how but it appears my serial port has renamed from ttyAMA0 to tty0.
And I still get permission denied when I try to open it in python.
Any further suggestions.

[boylesg]

Don't know how but it appears my serial port has renamed from ttyAMA0 to tty0.
And I still get permission denied when I try to open it in python.
Any further suggestions.

Actually what had happened here is that I disabled login over serial in raspi-config which apparently also disables the UART serial port as well.
So I went into config.txt and changed UART=0 to UART=1 and ttyAMA0 re-appeared.
And now when I open it in python it works!
And I can send text from the Python to the serial monitor of Arduino IDE.....cool.

If I send text the other way how does one view it in python?