Cannot open REPL terminal on my Ubuntu server

[banishlight]

I have a ESP32-CAM connected with the ESP32-CAM-MB adapter. On my macbook I can connect to my REPL terminal using
screen /dev/tty.usbserial-142420 115200
but on my Ubuntu server where I want to do my development I try
screen /dev/ttyUSB0 115200
and the terminal is just blank and I am not sure why...
I gave myself dialout permissions and I confirmed that it is connected using

sudo dmesg

I get the following:

[446863.355054] usb 3-7: new full-speed USB device number 4 using xhci_hcd
[446863.503894] usb 3-7: New USB device found, idVendor=1a86, idProduct=7523, bcdDevice= 2.64
[446863.503903] usb 3-7: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[446863.503907] usb 3-7: Product: USB Serial
[446863.504638] ch341 3-7:1.0: ch341-uart converter detected
[446863.505114] usb 3-7: ch341-uart converter now attached to ttyUSB0

not sure why it is acting different on this machine.

[ricksorensen]

/dev/ttyACM0 instead of /dev/ttyUSB0?

[davefes]

Hard reset is pressing the button by the 3V3 regulator.

[Josverl]

On ubuntu desktop I have the experience that I do need to remove the braille reader support as that driver has rather broad assumptions about what a braille reader is. It assumes that anything connected using a CP210x USB to UART Bridge is considered to be a braille reader , and it then locks that device.
The CP210X is often combined with a esp8266, but not exclusively, I 've seen many different combinations, including a few with an ESP32 IIRC.

While I complete agree that accessibility is part of an OS, it appears to be a rather assuming implementation.
note that I'm not sure if brltty is part of the server image as well, if not apt will let you know.

My documented fix is:
Remove conflicting packages

# remove braille support as it conflicts with esp8266
sudo apt remove brltty

[banishlight]

• With screen /dev/ttyUSB0 115200 && reset button
• rsusb
  no connection, blank display on my terminal...

[davefes]

When you do a rsusb do you get any messages?

Which camera firmware did you put on the ESP32-CAM and you removed the link for flashing.

[banishlight]

This is what I get from rsusb:

$ rsusb
Using buffer-size of 30
Connecting to /dev/ttyUSB0 (buffer-size 30)...
Trying to connect to REPL ....................Unable to connect to REPL
Welcome to rshell. Use Control-D (or the exit command) to exit rshell.

No MicroPython boards connected - use the connect command to add one

and I am not sure how to remove the link for flashing with the board that I am using to connect via usb

[shariltumin]

ESP32-CAM with ESP32-CAM-MB adapter will not give a REPL because the Linux serial driver sets RTS and DTR to high by default. This means that the board is in programming mode when connected to USB. This makes it easy to flash new firmware, but does not reset the board to normal operating mode.

This is what you can do (assuming the ESP32-CAM-MB is connected to /dev/ttyUSB0):

$ miniterm --rts 0 --dtr 0 /dev/ttyUSB0 115200

You are still in boot loader mode. We need to do a hard reset. Locate the reset button on the ESP32-CAM (underneath the PCB, marked RST, near the 5V PIN). Press this button to initiate a hard reset. The RST on the ESP32-CAM-MB does not work.

"Ctrl+alt+)" (which is Ctrl+]) to quit miniterm. Now

$ screen /dev/ttyUSB0 115200

will give you REPL after a few 'Enter' keystrokes, "Ctrl-a k" will quit screen.

Now all serial terminal programs; tio, mpremote, Thonny etc. will work normally.

Note that you can also try gtkterm -p /dev/ttyUSB0 and unset DTR and RTS from "Control signals" menu.

Hope this helps.

[banishlight]

You are absolutely right this actually got me into my REPL
miniterm --rts 0 --dtr 0 /dev/ttyUSB0 115200
incredible!
I still cannot connect using screen /dev/ttyUSB0 115200 but I will post what I find from here thank you :)