Installing a CP210x USB to Serial converter

[lilzz]

dmesg | grep tty
usb 6-2: cp210x converter now attached to ttyUSB0


then I started Putty
Putty configuration
/dev/ttyUSB0 baud:9600

connect (open)

But it complains unable to open serial port.

[B.Goode]

Maybe the user account you are using does not have permission to access /dev/ttyUSB0 ?

[scruss]

Yes, that's most likely. I've used CP210s without problems, and your system looks like it is doing the happy thing.

Check for this:

Code: Select all

$ groups
pi adm dialout cdrom sudo audio video plugdev games users netdev input indiecity
pi@rpi ~ $ ls -la /dev/ttyUSB0 
crw-rw---T 1 root dialout 188, 0 Mar 28 11:45 /dev/ttyUSB0

You need to be part of the ‘dialout’ group to have read/write access to the serial port.

[lilzz]

well, I did
groups
lilzz adm sudo dip plugdev lpadmin

so, I added

useradd -G dialout lilzz

but it complains
useradd: user 'lilzz' already exists

[lilzz]

I can't add myself to dialout group.
sudo usermod -a -G dialout lilzz

then I check with groups
dialout still not there

[scruss]

you need to log out and log back in again

[lilzz]

OK, my putty is finally launched now.

but it's a blank. it has a small green rectangular shape and nothing else.

I try to type in something but nothing shown.

[scruss]

Is the device you're talking to really 9600 baud?
Have you crossed TX with RX, and vice versa, to make the null modem connection work?

[lilzz]

OK, I got something back like this.

But I can't type any command. What does this mean from the picture I shown? Is the communication OK? I attached a ESP8266 wifi module to the CP201x.

[DirkS]

I attached a ESP8266 wifi module to the CP201x.

Apparently the default rate may depend on the firmware version (although the ones I have all started off at 9k6)
Try higher speeds, up to 115k2.
Another thing to be aware of is that ESPs expect a CR+LF for entering commands. I'm not sure if Putty does this by default.

[DougieLawson]

That sort of error usually means the baud rate is wrong.

[lilzz]

Ok, I set the baud rate to 115200, I see something now.

but I type AT, and hit enter button.

I expect to see OK as response but nothing happened.

what's CR+LF? same as enter button?

[DirkS]

what's CR+LF? same as enter button?

No, that depends on the system.
You will have to make Putty send both a carriage return and a linefeed when you hit enter.

IIRC There are settings in Putty about implied linefeed when sending, but I'm not 100% sure about that.