# Serial Console

## Output to Serial Console
Make sure the kernel is started with the following parameter…
```
console=ttyS0,115200
```

## Change Size (rows/cols)
Often the expected size of the TTY session isn't what you would want and feels constrained. You can change a bunch of setting using the `stty` command. Below will change the number of columns because that is what I most often feel I need to change…

```
stty cols 140
```

## Dual Output

It is possible to have the kernel write to both the standard pseudo-terminal (`tty0`) and the serial console (`ttyS0`) by adding the following kernel parameters…
```
console=ttyS0,9600 console=tty0
```

## View Console

It is possible to view serial console output using the `screen` command. With a USB-to-Serial adapter plugged in you may see a device called something like `/dev/tty.usbserial-AG0JL5ZB` that will act as the tty device.

```bash
screen /dev/tty.usbserial-AG0JL5ZB 115200,cs8,ixon
```

Parameters explained from `man screen`
  
| Parameter | Description|
|--------|-----------|
| `<baud_rate>` | This affects transmission as well as receive speed (usually 300, 1200, 9600 or 19200) |
| `cs8` or `cs7` | Specify the transmission of eight (or seven) bits per byte |
| `ixon` or `-ixon` | Enables (or disables) software flow-control (CTRL-S/CTRL-Q) for sending data |
| `ixoff` or `-ixon` | Enables (or disables) software flow-control for receiving data |
| `istrip` or `-istrip` | Clear (or keep) the eight bit in each received byte |