I've connected a USB to Serial bridge dongle, and running `dmesg | grep tty` outputted the following:

```
[    0.000000] console [tty0] enabled
[603199.380677] usb 2-2: cp210x converter now attached to ttyUSB0

```

So now I'm trying to write to it as per [the answer in this previous question](https://superuser.com/questions/191654/how-can-i-send-data-to-the-serial-port-from-a-linux-shell) by running the following:

```
cat hello.txt > /dev/ttyUSB0

```

and 

```
sudo cat hello.txt > /dev/ttyUSB0

```

But both result in the following error:

```
bash: /dev/ttyUSB0: Permission denied

```

What am I doing wrong?

Thanks