build/documentation/Enabling_hardware_features.md

Enable Hardware Features
========================

Some boards require some manual configuration to turn on/off certain features

In some cases, the procedure is "less than obvious", so we document some basic examples here.

# Generic howto for Allwinner devices

## Legacy or Vanilla kernel ?

Many Armbian images come in two flavours : Legacy (using an older kernel version) and Vanilla (up-to-date kernel). Depending on kernel version, the procedure to enable/disable features is not the same :
 * Legacy kernel : FEX
 * Vanilla kernel : DT (Device Tree)

## What flavour am I using ?

Best way to know is by checking your kernel version :

```
root@bananapipro:~# uname -a
Linux bananapipro 4.5.2-sunxi #11 SMP Thu Apr 28 21:53:25 CEST 2016 armv7l GNU/Linux
```

In this example the kernel version is 4.5.2 so you can use DT to tweak some settings. If you get a kernel version 3.X then you'll be certainly using FEX like on an Orange Pi Plus 2E :

```
root@orangepiplus2e:~# uname -a
Linux orangepiplus2e 3.4.112-sun8i #10 SMP PREEMPT Wed Jun 1 19:43:08 CEST 2016 armv7l GNU/Linux
```

## FEX

### Which file should I edit

Armbian embed a lot of BIN files, but a symlink point to the one in use :

```
root@orangepiplus2e:~# ls -la /boot/script.bin
lrwxrwxrwx 1 root root 22 Jun  1 20:30 /boot/script.bin -> bin/orangepiplus2e.bin
```

### Updating a FEX

You may need to use `sudo` with all the following commands.

The whole process won't overwrite any of your files. If you're paranoid, you can make a proper backup of your BIN file :

```
cp /boot/script.bin /boot/bin/script.bin.backup
```

Then you can decompile your BIN into a FEX :

```
bin2fex /boot/script.bin /tmp/custom.fex
```

Finally you can edit your FEX file with your favorite text editor and compile it back to a BIN :

```
fex2bin /tmp/custom.fex /boot/bin/custom.bin
```

The last step is to change the symlink to use your custom BIN :

```
ln -sf /boot/bin/custom.bin /boot/script.bin
```

## Device Tree

### Which file should I edit

I use the following command and try to guess which file to use in `/boot/dtb/` :

```
cat /proc/device-tree/model
```

# H3 based Orange Pi, legacy kernel

## Enable serial /dev/ttyS3 on pins 8 and 10 of the 40 pin header

Update the FEX configuration (which is compiled into a .bin) located at /boot/script.bin

Decompile .bin to .fex
```
cd /boot
bin2fex script.bin > custom.fex
rm script.bin # only removes symbolic link
```

Edit .fex file
```
[uart3]
uart_used = 1 ; Change from 0 to 1
uart_port = 3
uart_type = 2 ; In this case we have a 2 pin UART
uart_tx = port:PA13<3><1><default><default>
uart_rx = port:PA14<3><1><default><default>
```

Compile .fex to .bin
```
fex2bin custom.fex > script.bin
```

Reboot

Notice that /dev/ttyS3 appears. That is your new UART device.

****